JP6800301B2 - How to drive drive devices, air conditioners and electric motors - Google Patents

Description

The present invention relates to a drive device for driving an electric motor, an air conditioner having an electric motor, and a method for driving the electric motor.

Regarding the electric motor used in air conditioners, etc., in order to improve the operating efficiency at low speed rotation and high speed rotation, the connection state of the coil of the electric motor is Y connection (star connection) and delta connection (also called triangular connection or Δ connection). (For example, see Patent Document 1).

Specifically, control is performed in which the rotation speed of the electric motor is compared with the threshold value, and when the rotation speed is higher or lower than the threshold value for a certain period of time, the Y connection is switched to the delta connection (for example). , Patent Document 2).

JP-A-2009-216324 Japanese Patent No. 4619826

However, it is difficult to sufficiently improve the efficiency of the electric motor simply by switching between the Y connection and the delta connection.

The present invention has been made to solve the above problems, and an object of the present invention is to sufficiently improve the efficiency of an electric motor.

The drive device of the present invention is a drive device used in an air conditioner to drive an electric motor having a coil, and includes a converter that generates a bus voltage and an inverter that converts the bus voltage into an AC voltage and supplies the coil. , A connection switching unit for switching the connection state of the coil is provided. The coil connection state includes a first connection state and a second connection state, and the inverter outputs a line voltage lower in the second connection state than in the first connection state. In the heating intermediate condition, connection state of the coils is a first connection state, and bus voltage for the converter to produce the Ru first bus voltage V1 der. Under the heating rated conditions, the coil connection state is the second connection state, and the bus voltage generated by the converter is the second bus voltage V2, which is higher than the first bus voltage V1.

According to the present invention, the converter outputs the first bus voltage V1 under the heating intermediate condition and outputs the second bus voltage V2 higher than the first bus voltage V1 under the heating rated condition, so that the motor efficiency is improved. It can be improved sufficiently.

It is sectional drawing which shows the structure of the electric motor of Embodiment 1. FIG. It is sectional drawing which shows the structure of the rotary compressor of Embodiment 1. FIG. It is a block diagram which shows the structure of the air conditioner of Embodiment 1. FIG. It is a conceptual diagram which shows the basic structure of the control system of the air conditioner of Embodiment 1. FIG. It is a block diagram (A) which shows the control system of the air conditioner of Embodiment 1, and block diagram (B) which shows the part which controls the electric motor of a compressor based on a room temperature. It is a block diagram which shows the structure of the drive device of Embodiment 1. FIG. It is a block diagram which shows the structure of the drive device of Embodiment 1. FIG. It is a schematic diagram (A) and (B) which shows the switching operation of the connection state of the coil of Embodiment 1. FIG. It is a schematic diagram which shows the connection state of the coil of Embodiment 1. FIG. It is a flowchart which shows the basic operation of the air conditioner of Embodiment 1. It is a flowchart which shows the connection switching operation of the air conditioner of Embodiment 1. It is a flowchart which shows the connection switching operation of the air conditioner of Embodiment 1. It is a flowchart (A) and (B) which shows another example of the connection switching operation of the air conditioner of Embodiment 1. FIG. It is a timing chart which shows an example of the operation of the air conditioner of Embodiment 1. FIG. It is a graph which shows the relationship between the line voltage and the rotation speed when a coil is connected by Y connection in an electric motor. It is a graph which shows the relationship between the line voltage and the rotation speed when a coil is connected by Y connection in an electric motor, and field weakening control is performed. It is a graph which shows the relationship between the motor efficiency and the rotation speed when the field weakening control shown in FIG. 16 is performed. It is a graph which shows the relationship between the electric motor torque and the rotation speed when the field weakening control shown in FIG. 16 is performed. It is a graph which shows the relationship between the line voltage and the rotation speed in each of the case where the connection state of the coil is Y connection and the case where it is delta connection. It is a graph which shows the relationship between the line voltage and the rotation speed when switching from Y connection to delta connection. It is a graph which shows the relationship between the motor efficiency and the rotation speed in each of the case where the connection state of the coil is Y connection and the case where it is delta connection. The motor efficiency when the coil connection state is Y connection, the number of turns is adjusted so that the line voltage reaches the inverter maximum output voltage at a rotation speed slightly smaller than the heating intermediate condition, and the Y connection is switched to the delta connection. It is a graph which shows the relationship between and the number of rotations. It is a graph which shows the relationship between the motor torque and the rotation speed in each of the case where the connection state of the coil is Y connection and the case where it is delta connection. The coil connection state is Y connection, the number of turns is adjusted so that the line voltage reaches the maximum output voltage of the inverter at a rotation speed slightly smaller than the heating intermediate condition, and the motor torque when switching from Y connection to delta connection. It is a graph which shows the relationship between and the number of rotations. It is a graph which shows the relationship between the line voltage and the rotation speed when the bus voltage is switched by a converter. FIG. 5 is a graph showing the relationship between the line voltage and the rotation speed when the coil connection state is switched and the bus voltage of the converter is switched in the first embodiment. It is a graph which shows the relationship between the motor efficiency and the rotation speed in each of the case where the connection state of the coil is Y connection and the case where it is delta connection. FIG. 5 is a graph showing the relationship between the motor efficiency and the rotation speed when the coil connection state is switched and the bus voltage of the converter is switched in the first embodiment. It is a graph which shows the relationship between the motor torque and the rotation speed in each of the case where the connection state of the coil is Y connection and the case where it is delta connection. FIG. 5 is a graph showing the relationship between the motor efficiency and the rotation speed when the coil connection state is switched and the bus voltage of the converter is switched in the first embodiment. It is a graph (A), (B) which shows the relationship between the electric motor efficiency and the rotation speed in the 1st modification of Embodiment 1. It is a graph which shows the relationship between the line voltage and the rotation speed in the 2nd modification of Embodiment 1. It is a schematic diagram (A), (B) for demonstrating the operation of switching the connection state of the coil of the 3rd modification of Embodiment 1. FIG. It is a schematic diagram (A), (B) for demonstrating another example of the coil connection state switching operation of the 3rd modification of Embodiment 1. FIG. It is a flowchart which shows the connection switching operation in 4th modification of Embodiment 1. FIG. It is a flowchart which shows the connection switching operation in 5th modification of Embodiment 1. FIG. It is a block diagram which shows the structure of the air conditioner of Embodiment 2. It is a block diagram which shows the control system of the air conditioner of Embodiment 2. It is a block diagram which shows the control system of the drive device of Embodiment 2. It is a flowchart which shows the basic operation of the air conditioner of Embodiment 2. It is a flowchart which shows the basic operation of the air conditioner of the modification of Embodiment 2.

Embodiment 1.
<Composition of electric motor>
Embodiment 1 of the present invention will be described. FIG. 1 is a cross-sectional view showing the configuration of the electric motor 1 according to the first embodiment of the present invention. The electric motor 1 is a permanent magnet embedded motor, and is used, for example, in a rotary compressor. The electric motor 1 includes a stator 10 and a rotor 20 rotatably provided inside the stator 10. An air gap of, for example, 0.3 to 1 mm is formed between the stator 10 and the rotor 20. Note that FIG. 1 is a cross-sectional view of a plane orthogonal to the rotation axis of the rotor 20.

Hereinafter, the axial direction (direction of the rotation axis) of the rotor 20 is simply referred to as "axial direction". Further, the direction along the outer circumference (circumference) of the stator 10 and the rotor 20 is simply referred to as "circumferential direction". The radial direction of the stator 10 and the rotor 20 is simply referred to as the "diameter direction".

The stator 10 includes a stator core 11 and a coil 3 wound around the stator core 11. The stator core 11 is formed by laminating a plurality of electromagnetic steel plates having a thickness of 0.1 to 0.7 mm (here, 0.35 mm) in the direction of the rotation axis and fastening them by caulking.

The stator core 11 has an annular yoke portion 13 and a plurality of (here, nine) tooth portions 12 projecting radially inward from the yoke portion 13. Slots are formed between the adjacent tooth portions 12. Each tooth portion 12 has a tooth tip portion having a wide width (dimension in the circumferential direction of the stator core 11) at the tip inside in the radial direction.

A coil 3 which is a stator winding is wound around each tooth portion 12 via an insulator (insulator) 14. The coil 3 is, for example, a magnet wire having a wire diameter (diameter) of 0.8 mm wound around each tooth portion 12 in a concentrated manner by 110 turns (110 turns). The number of turns and the wire diameter of the coil 3 are determined according to the characteristics (rotation speed, torque, etc.) required for the motor 1, the supply voltage, or the cross-sectional area of the slot.

The coil 3 is composed of U-phase, V-phase and W-phase three-phase windings (referred to as coils 3U, 3V, 3W). Both terminals of the coil 3 of each phase are open. That is, the coil 3 has a total of six terminals. The connection state of the coil 3 is configured to be switchable between Y connection and delta connection, as will be described later. The insulator 14 is made of, for example, a film formed of PET (polyethylene terephthalate) and has a thickness of 0.1 to 0.2 mm.

The stator core 11 has a configuration in which a plurality of (here, nine) blocks are connected via a thin wall portion. With the stator core 11 unfolded in a strip shape, a magnet wire is wound around each tooth portion 12, and then the stator core 11 is bent in an annular shape to weld both ends.

It is effective in increasing the number of turns of the coil 3 in the slot that the insulator 14 is made of a thin film and the stator core 11 has a divided structure so that the insulator 14 can be easily wound. The stator core 11 is not limited to the one having a configuration in which a plurality of blocks (divided cores) are connected as described above.

The rotor 20 has a rotor core 21 and a permanent magnet 25 attached to the rotor core 21. The rotor core 21 is formed by laminating a plurality of electromagnetic steel plates having a thickness of 0.1 to 0.7 mm (here, 0.35 mm) in the direction of the rotation axis and fastening them by caulking.

The rotor core 21 has a cylindrical shape, and a shaft hole 27 (center hole) is formed at the center in the radial direction thereof. A shaft serving as a rotation shaft of the rotor 20 (for example, the shaft 90 of the rotary compressor 8) is fixed to the shaft hole 27 by shrink fitting or press fitting.

Along the outer peripheral surface of the rotor core 21, a plurality of (here, six) magnet insertion holes 22 into which the permanent magnets 25 are inserted are formed. The magnet insertion hole 22 is a gap, and one magnet insertion hole 22 corresponds to one magnetic pole. Since six magnet insertion holes 22 are provided here, the rotor 20 as a whole has six poles.

Here, the magnet insertion hole 22 has a V-shape in which the central portion in the circumferential direction protrudes inward in the radial direction. The magnet insertion hole 22 is not limited to the V shape, and may be, for example, a straight shape.

Two permanent magnets 25 are arranged in one magnet insertion hole 22. That is, two permanent magnets 25 are arranged for one magnetic pole. Here, since the rotor 20 has 6 poles as described above, a total of 12 permanent magnets 25 are arranged.

The permanent magnet 25 is a flat plate-shaped member that is long in the axial direction of the rotor core 21, has a width in the circumferential direction of the rotor core 21, and has a thickness in the radial direction. The permanent magnet 25 is composed of, for example, a rare earth magnet containing neodymium (Nd), iron (Fe) and boron (B) as main components.

The permanent magnet 25 is magnetized in the thickness direction. Further, the two permanent magnets 25 arranged in one magnet insertion hole 22 are magnetized so that the same magnetic poles face the same side in the radial direction.

Flux barriers 26 are formed on both sides of the magnet insertion hole 22 in the circumferential direction. The flux barrier 26 is a gap continuously formed in the magnet insertion hole 22. The flux barrier 26 is for suppressing the leakage flux between adjacent magnetic poles (that is, the magnetic flux flowing through the poles).

In the rotor core 21, a first magnet holding portion 23, which is a protrusion, is formed at the central portion in the circumferential direction of each magnet insertion hole 22. Further, in the rotor core 21, second magnet holding portions 24, which are protrusions, are formed at both ends of the magnet insertion hole 22 in the circumferential direction. The first magnet holding portion 23 and the second magnet holding portion 24 position and hold the permanent magnet 25 in each magnet insertion hole 22.

As described above, the number of slots of the stator 10 (that is, the number of teeth portions 12) is 9, and the number of poles of the rotor 20 is 6. That is, in the electric motor 1, the ratio of the number of poles of the rotor 20 to the number of slots of the stator 10 is 2: 3.

In the electric motor 1, the connection state of the coil 3 is switched between the Y connection and the delta connection, but when the delta connection is used, a circulating current may flow and the performance of the electric motor 1 may deteriorate. The circulating current is due to the third harmonic generated in the induced voltage in the windings of each phase. In the case of concentrated winding in which the ratio of the number of poles to the number of slots is 2: 3, no third harmonic is generated in the induced voltage unless there is an influence such as magnetic saturation, and therefore performance deterioration due to circulating current occurs. It is known that there is no such thing.

<Structure of rotary compressor>
Next, the rotary compressor 8 using the electric motor 1 will be described. FIG. 2 is a cross-sectional view showing the configuration of the rotary compressor 8. The rotary compressor 8 includes a shell 80, a compression mechanism 9 arranged in the shell 80, and an electric motor 1 for driving the compression mechanism 9. The rotary compressor 8 further has a shaft 90 (crankshaft) that connects the electric motor 1 and the compression mechanism 9 so as to be able to transmit power. The shaft 90 fits into the shaft hole 27 (FIG. 1) of the rotor 20 of the electric motor 1.

The shell 80 is, for example, a closed container made of a steel plate and covers the electric motor 1 and the compression mechanism 9. The shell 80 has an upper shell 80a and a lower shell 80b. The upper shell 80a has a glass terminal 81 as a terminal for supplying electric power from the outside of the rotary compressor 8 to the electric motor 1, and a discharge pipe for discharging the refrigerant compressed in the rotary compressor 8 to the outside. 85 and is attached. Here, a total of six lead wires corresponding to two U-phase, two V-phase, and two W-phase coils 3 of the motor 1 (FIG. 1) are drawn from the glass terminal 81. The electric motor 1 and the compression mechanism 9 are housed in the lower shell 80b.

The compression mechanism 9 has an annular first cylinder 91 and a second cylinder 92 along the shaft 90. The first cylinder 91 and the second cylinder 92 are fixed to the inner peripheral portion of the shell 80 (lower shell 80b). An annular first piston 93 is arranged on the inner peripheral side of the first cylinder 91, and an annular second piston 94 is arranged on the inner peripheral side of the second cylinder 92. The first piston 93 and the second piston 94 are rotary pistons that rotate together with the shaft 90.

A partition plate 97 is provided between the first cylinder 91 and the second cylinder 92. The partition plate 97 is a disk-shaped member having a through hole in the center. The cylinder chambers of the first cylinder 91 and the second cylinder 92 are provided with vanes (not shown) that divide the cylinder chamber into a suction side and a compression side. The first cylinder 91, the second cylinder 92, and the partition plate 97 are integrally fixed by bolts 98.

An upper frame 95 is arranged above the first cylinder 91 so as to close the upper side of the cylinder chamber of the first cylinder 91. A lower frame 96 is arranged below the second cylinder 92 so as to close the lower side of the cylinder chamber of the second cylinder 92. The upper frame 95 and the lower frame 96 rotatably support the shaft 90.

Refrigerating machine oil (not shown) that lubricates each sliding portion of the compression mechanism 9 is stored in the bottom of the lower shell 80b of the shell 80. Refrigerating machine oil rises in the holes 90a formed in the axial direction inside the shaft 90, and is supplied to each sliding portion from the oil supply holes 90b formed at a plurality of positions of the shaft 90.

The stator 10 of the electric motor 1 is attached to the inside of the shell 80 by shrink fitting. The coil 3 of the stator 10 is connected to the glass terminal 81 attached to the upper shell 80a.
Power is supplied. A shaft 90 is fixed to the shaft hole 27 (FIG. 1) of the rotor 20.

An accumulator 87 for storing the refrigerant gas is attached to the shell 80. The accumulator 87 is held, for example, by a holding portion 80c provided on the outside of the lower shell 80b. A pair of suction pipes 88 and 89 are attached to the shell 80, and refrigerant gas is supplied from the accumulator 87 to the cylinders 91 and 92 via the suction pipes 88 and 89.

As the refrigerant, for example, R410A, R407C, R22, or the like may be used, but from the viewpoint of preventing global warming, it is desirable to use a refrigerant having a low GWP (global warming potential). As the low GWP refrigerant, for example, the following refrigerants can be used.

(1) First, a halogenated hydrocarbon having a carbon double bond in the composition, for example, HFO (Hydro-Fluoro-Orefin) -1234yf (CF3CF = CH2) can be used. The GWP of HFO-1234yf is 4.
(2) Further, a hydrocarbon having a carbon double bond in the composition, for example, R1270 (propylene) may be used. The GWP of R1270 is 3, which is lower than HFO-1234yf but higher in flammability than HFO-1234yf.
(3) Further, a mixture containing at least one of a halogenated hydrocarbon having a carbon double bond in the composition or a hydrocarbon having a carbon double bond in the composition, for example, a mixture of HFO-1234yf and R32. You may use it. Since the above-mentioned HFO-1234yf is a low-pressure refrigerant, the pressure loss tends to be large, which may lead to deterioration of the performance of the refrigeration cycle (particularly the evaporator). Therefore, it is practically desirable to use a mixture with R32 or R41, which is a higher pressure refrigerant than HFO-1234yf.

The basic operation of the rotary compressor 8 is as follows. The refrigerant gas supplied from the accumulator 87 is supplied to the cylinder chambers of the first cylinder 91 and the second cylinder 92 through the suction pipes 88 and 89. When the electric motor 1 is driven and the rotor 20 rotates, the shaft 90 rotates together with the rotor 20. Then, the first piston 93 and the second piston 94 fitted to the shaft 90 rotate eccentrically in each cylinder chamber to compress the refrigerant in each cylinder chamber. The compressed refrigerant rises in the shell 80 through a hole (not shown) provided in the rotor 20 of the electric motor 1 and is discharged to the outside from the discharge pipe 85.

<Composition of air conditioner>
Next, the air conditioner 5 including the drive device of the first embodiment will be described. FIG. 3 is a block diagram showing the configuration of the air conditioner 5. The air conditioner 5 includes an indoor unit 5A installed indoors (space subject to air conditioning) and an outdoor unit 5B installed outdoors. The indoor unit 5A and the outdoor unit 5B are connected by connecting pipes 40a and 40b through which the refrigerant flows. The liquid refrigerant that has passed through the condenser flows through the connection pipe 40a. The gas refrigerant that has passed through the evaporator flows through the connecting pipe 40b.

The outdoor unit 5B includes a compressor 41 that compresses and discharges the refrigerant, a four-way valve (refrigerant flow path switching valve) 42 that switches the flow direction of the refrigerant, and an outdoor heat exchanger 43 that exchanges heat between the outside air and the refrigerant. And an expansion valve (compressor) 44 for reducing the pressure of the high-pressure refrigerant to a low pressure are arranged. The compressor 41 is composed of the rotary compressor 8 (FIG. 2) described above. An indoor heat exchanger 45 that exchanges heat between the indoor air and the refrigerant is arranged in the indoor unit 5A.

The compressor 41, the four-way valve 42, the outdoor heat exchanger 43, the expansion valve 44, and the indoor heat exchanger 45 are connected by a pipe 40 including the connection pipes 40a and 40b described above to form a refrigerant circuit. These components constitute a compression refrigeration cycle (compression heat pump cycle) in which the refrigerant is circulated by the compressor 41.

In order to control the operation of the air conditioner 5, an indoor control device 50a is arranged in the indoor unit 5A, and an outdoor control device 50b is arranged in the outdoor unit 5B. The indoor control device 50a and the outdoor control device 50b each have a control board on which various circuits for controlling the air conditioner 5 are formed. The indoor control device 50a and the outdoor control device 50b are connected to each other by a connecting cable 50c. The connecting cable 50c is bundled together with the connection pipes 40a and 40b described above.

In the outdoor unit 5B, an outdoor blower fan 46, which is a blower, is arranged so as to face the outdoor heat exchanger 43. The outdoor blower fan 46 rotates to generate an air flow that passes through the outdoor heat exchanger 43. The outdoor blower fan 46 is composed of, for example, a propeller fan.

The four-way valve 42 is controlled by the outdoor control device 50b to switch the flow direction of the refrigerant. When the four-way valve 42 is in the position shown by the solid line in FIG. 3, the gas refrigerant discharged from the compressor 41 is sent to the outdoor heat exchanger 43 (condenser). On the other hand, when the four-way valve 42 is at the position shown by the broken line in FIG. 3, the gas refrigerant flowing in from the outdoor heat exchanger 43 (evaporator) is sent to the compressor 41. The expansion valve 44 is controlled by the outdoor control device 50b, and the high-pressure refrigerant is reduced to a low pressure by changing the opening degree.

In the indoor unit 5A, an indoor blower fan 47, which is a blower, is arranged so as to face the indoor heat exchanger 45. The indoor blower fan 47 rotates to generate an air flow that passes through the indoor heat exchanger 45. The indoor blower fan 47 is composed of, for example, a cross flow fan.

The indoor unit 5A is provided with an indoor temperature sensor 54 as a temperature sensor that measures the indoor temperature Ta, which is the air temperature in the room (space subject to air conditioning), and sends the measured temperature information (information signal) to the indoor control device 50a. ing. The indoor temperature sensor 54 may be composed of a temperature sensor used in a general air conditioner, or may use a radiant temperature sensor that detects the surface temperature of a wall or floor in the room.

The indoor unit 5A is also provided with a signal receiving unit 56 that receives an instruction signal (driving instruction signal) transmitted from a remote controller 55 (remote control device) operated by the user. The remote controller 55 causes the user to instruct the air conditioner 5 of operation input (operation start and stop) or operation content (set temperature, wind speed, etc.).

The compressor 41 is configured so that the operating rotation speed can be changed in the range of 20 to 130 rps during normal operation. As the rotation speed of the compressor 41 increases, the amount of refrigerant circulating in the refrigerant circuit increases. The rotation speed of the compressor 41 is determined by the control device 50 (more specifically, according to the temperature difference ΔT between the current indoor temperature Ta obtained by the indoor temperature sensor 54 and the set temperature Ts set by the user on the remote controller 55. , The outdoor control device 50b) controls. The larger the temperature difference ΔT, the higher the rotation speed of the compressor 41, which increases the circulation amount of the refrigerant.

The rotation of the indoor blower fan 47 is controlled by the indoor control device 50a. The rotation speed of the indoor blower fan 47 can be switched in a plurality of stages. Here, for example, the rotation speed can be switched in three stages of strong wind, medium wind, and weak wind. When the wind speed setting is set to the automatic mode on the remote controller 55, the rotation speed of the indoor blower fan 47 is switched according to the temperature difference ΔT between the measured indoor temperature Ta and the set temperature Ts.

The rotation of the outdoor blower fan 46 is controlled by the outdoor control device 50b. The rotation speed of the outdoor blower fan 46 can be switched in a plurality of stages. Here, the rotation speed of the outdoor blower fan 46 is switched according to the temperature difference ΔT between the measured indoor temperature Ta and the set temperature Ts.

The indoor unit 5A also includes a left and right wind direction plate 48 and a vertical wind direction plate 49. The left and right wind direction plates 48 and the upper and lower wind direction plates 49 change the blowing direction when the conditioned air heat exchanged by the indoor heat exchanger 45 is blown into the room by the indoor blower fan 47. The left and right wind direction plates 48 change the blowing direction to the left and right, and the vertical wind direction plate 49 changes the blowing direction up and down. The angles of the left and right wind direction plates 48 and the vertical wind direction plates 49, that is, the wind direction of the blown airflow, are controlled by the indoor control device 50a based on the settings of the remote controller 55.

The basic operation of the air conditioner 5 is as follows. During the cooling operation, the four-way valve 42 is switched to the position indicated by the solid line, and the high-temperature and high-pressure gas refrigerant discharged from the compressor 41 flows into the outdoor heat exchanger 43. In this case, the outdoor heat exchanger 43 operates as a condenser. When air passes through the outdoor heat exchanger 43 due to the rotation of the outdoor blower fan 46, the heat of condensation of the refrigerant is taken away by heat exchange. The refrigerant condenses to become a high-pressure low-temperature liquid refrigerant, and adiabatic expansion at the expansion valve 44 to become a low-pressure low-temperature two-phase refrigerant.

The refrigerant that has passed through the expansion valve 44 flows into the indoor heat exchanger 45 of the indoor unit 5A. The indoor heat exchanger 45 operates as an evaporator. When the air passes through the indoor heat exchanger 45 due to the rotation of the indoor blower fan 47, the heat of vaporization is taken away by the refrigerant by the heat exchange, and the cooled air is supplied to the room. The refrigerant evaporates to become a low-temperature low-pressure gas refrigerant, which is again compressed into a high-temperature and high-pressure refrigerant by the compressor 41.

During the heating operation, the four-way valve 42 is switched to the position indicated by the dotted line, and the high-temperature and high-pressure gas refrigerant discharged from the compressor 41 flows into the indoor heat exchanger 45. In this case, the indoor heat exchanger 45 operates as a condenser. When the air passes through the indoor heat exchanger 45 due to the rotation of the indoor blower fan 47, the heat exchange removes the heat of condensation from the refrigerant, whereby the heated air is supplied to the room. Further, the refrigerant condenses into a high-pressure low-temperature liquid refrigerant, and adiabatic expansion is performed by the expansion valve 44 to become a low-pressure low-temperature two-phase refrigerant.

The refrigerant that has passed through the expansion valve 44 flows into the outdoor heat exchanger 43 of the outdoor unit 5B. The outdoor heat exchanger 43 operates as an evaporator. When air passes through the outdoor heat exchanger 43 due to the rotation of the outdoor blower fan 46, the heat of vaporization is taken away by the refrigerant by heat exchange. The refrigerant evaporates to become a low-temperature low-pressure gas refrigerant, which is again compressed into a high-temperature and high-pressure refrigerant by the compressor 41.

FIG. 4 is a conceptual diagram showing the basic configuration of the control system of the air conditioner 5. The indoor control device 50a and the outdoor control device 50b described above exchange information with each other via a communication cable 50c to control the air conditioner 5. Here, the indoor control device 50a and the outdoor control device 50b are collectively referred to as a control device 50.

FIG. 5A is a block diagram showing a control system of the air conditioner 5. The control device 50 is composed of, for example, a microcomputer. The control device 50 incorporates an input circuit 51, an arithmetic circuit 52, and an output circuit 53.

The instruction signal received from the remote controller 55 by the signal receiving unit 56 is input to the input circuit 51. The instruction signal includes, for example, a signal for setting an operation input, an operation mode, a set temperature, an air volume or a wind direction. In addition, temperature information representing the indoor temperature detected by the indoor temperature sensor 54 is input to the input circuit 51. The input circuit 51 outputs these input information to the arithmetic circuit 52.

The arithmetic circuit 52 has a CPU (Central Processing Unit) 57 and a memory 58. The CPU 57 performs arithmetic processing and determination processing. The memory 58 stores various set values and programs used for controlling the air conditioner 5. The arithmetic circuit 52 performs arithmetic and determination based on the information input from the input circuit 51, and outputs the result to the output circuit 53.

The output circuit 53 includes a compressor 41, a connection switching unit 60 (described later), a converter 102, an inverter 103, a compressor 41, a four-way valve 42, an expansion valve 44, and an outdoor blower fan based on the information input from the arithmetic circuit 52. A control signal is output to the 46, the indoor blower fan 47, the left and right wind direction plates 48, and the up and down wind direction plates 49.

As described above, the indoor control device 50a and the outdoor control device 50b (FIG. 4) exchange information with each other via the communication cable 50c to control various devices of the indoor unit 5A and the outdoor unit 5B. Here, the indoor control device 50a and the outdoor control device 50b are collectively referred to as the control device 50. In reality, each of the indoor control device 50a and the outdoor control device 50b is composed of a microcomputer. A control device may be mounted on only one of the indoor unit 5A and the outdoor unit 5B to control various devices of the indoor unit 5A and the outdoor unit 5B.

FIG. 5B is a block diagram showing a portion of the control device 50 that controls the electric motor 1 of the compressor 41 based on the room temperature Ta. The calculation circuit 52 of the control device 50 includes a reception content analysis unit 52a, a room temperature acquisition unit 52b, a temperature difference calculation unit 52c, and a compressor control unit 52d. These are included in the CPU 57 of the arithmetic circuit 52, for example.

The reception content analysis unit 52a analyzes the instruction signal input from the remote controller 55 via the signal reception unit 56 and the input circuit 51. The reception content analysis unit 52a outputs, for example, the operation mode and the set temperature Ts to the temperature difference calculation unit 52c based on the analysis result. The indoor temperature acquisition unit 52b acquires the indoor temperature Ta input from the indoor temperature sensor 54 via the input circuit 51 and outputs it to the temperature difference calculation unit 52c.

The temperature difference calculation unit 52c calculates the temperature difference ΔT between the room temperature Ta input from the room temperature acquisition unit 52b and the set temperature Ts input from the reception content analysis unit 52a. When the operation mode input from the reception content analysis unit 52a is the heating operation, the temperature difference is calculated by ΔT = Ts−Ta. When the operation mode is cooling operation, it is calculated by the temperature difference ΔT = Ta−Ts. The temperature difference calculation unit 52c outputs the calculated temperature difference ΔT to the compressor control unit 52d.

The compressor control unit 52d controls the drive device 100 based on the temperature difference ΔT input from the temperature difference calculation unit 52c, thereby controlling the rotation speed of the electric motor 1 (that is, the rotation speed of the compressor 41).

<Configuration of drive unit>
Next, the drive device 100 for driving the electric motor 1 will be described. FIG. 6 is a block diagram showing the configuration of the drive device 100. The drive device 100 includes a converter 102 that rectifies the output of the power supply 101, an inverter 103 that outputs an AC voltage to the coil 3 of the electric motor 1, a connection switching unit 60 that switches the connection state of the coil 3, and a control device 50. It is composed of. Power is supplied to the converter 102 from a power source 101, which is an alternating current (AC) power source.

The power supply 101 is, for example, an AC power supply of 200 V (effective voltage). The converter 102 is a rectifier circuit and outputs a direct current (DC) voltage of, for example, 280 V. The voltage output from the converter 102 is referred to as a bus voltage. The inverter 103 is supplied with a bus voltage from the converter 102, and outputs a line voltage (also referred to as a motor voltage) to the coil 3 of the motor 1. Wiring 104, 105, 106 connected to the coils 3U, 3V, and 3W are connected to the inverter 103, respectively.

The coil 3U has terminals 31U and 32U. The coil 3V has terminals 31V and 32V. The coil 3W has terminals 31W and 32W. The wiring 104 is connected to the terminal 31U of the coil 3U. The wiring 105 is connected to the terminal 31V of the coil 3V. The wiring 106 is connected to the terminal 31W of the coil 3W.

The connection switching unit 60 has switches 61, 62, 63. The switch 61 connects the terminal 32U of the coil 3U to either the wiring 105 or the neutral point 33. The switch 62 connects the terminal 32V of the coil 3V to either the wiring 106 or the neutral point 33. The switch 63 connects the terminal 32W of the coil 3W to either the wiring 104 or the neutral point 33. The switches 61, 62, and 63 of the connection switching unit 60 are composed of relay contacts here. However, it may be composed of a semiconductor switch.

The control device 50 controls the converter 102, the inverter 103, and the connection switching unit 60. The configuration of the control device 50 is as described with reference to FIG. The operation instruction signal from the remote controller 55 received by the signal receiving unit 56 and the indoor temperature detected by the indoor temperature sensor 54 are input to the control device 50. Based on these input information, the control device 50 outputs a voltage switching signal to the converter 102, outputs an inverter drive signal to the inverter 103, and outputs a connection switching signal to the connection switching unit 60.

In the state shown in FIG. 6, the switch 61 has the terminal 32U of the coil 3U connected to the neutral point 33, and the switch 62 has the terminal 32V of the coil 3V connected to the neutral point 33. Connects the terminal 32W of the coil 3W to the neutral point 33. That is, the terminals 31U, 31V, 31W of the coils 3U, 3V, 3W are connected to the inverter 103, and the terminals 32U, 32V, 32W are connected to the neutral point 33.

FIG. 7 is a block diagram showing a state in which the switches 61, 62, and 63 of the connection switching unit 60 are switched in the drive device 100. In the state shown in FIG. 7, the switch 61 connects the terminal 32U of the coil 3U to the wiring 105, the switch 62 connects the terminal 32V of the coil 3V to the wiring 106, and the switch 63 connects the coil 3W. Terminal 32W is connected to the wiring 104.

FIG. 8A is a schematic view showing the connection state of the coils 3U, 3V, and 3W when the switches 61, 62, and 63 are in the state shown in FIG. The coils 3U, 3V and 3W are connected to the neutral point 33 at the terminals 32U, 32V and 32W, respectively. Therefore, the connection state of the coils 3U, 3V, and 3W is Y connection (star connection).

FIG. 8B is a schematic view showing the connection state of the coils 3U, 3V, and 3W when the switches 61, 62, and 63 are in the state shown in FIG. 7. The terminal 32U of the coil 3U is connected to the terminal 31V of the coil 3V via the wiring 105 (FIG. 7). The terminal 32V of the coil 3V is connected to the terminal 31W of the coil 3W via the wiring 106 (FIG. 7). The terminal 32W of the coil 3W is connected to the terminal 31U of the coil 3U via the wiring 104 (FIG. 7). Therefore, the connection state of the coils 3U, 3V, and 3W is a delta connection (triangular connection).

In this way, the connection switching unit 60 changes the connection state of the coils 3U, 3V, 3W of the motor 1 to the Y connection (first connection state) and the delta connection (second connection state) by switching the switches 61, 62, 63. It can be switched between (connection state) and.

FIG. 9 is a schematic view showing each coil portion of the coils 3U, 3V, and 3W. As described above, the electric motor 1 has nine tooth portions 12 (FIG. 1), and the coils 3U, 3V, and 3W are each wound around the three tooth portions 12. That is, the coil 3U is formed by connecting the U-phase coil portions Ua, Ub, and Uc wound around the three teeth portions 12 in series. Similarly, the coil 3V is formed by connecting the V-phase coil portions Va, Vb, and Vc wound around the three tooth portions 12 in series. Further, the coil 3W is formed by connecting W-phase coil portions Wa, Wb, and Wc wound around the three teeth portions 12 in series.

<Operation of air conditioner>
10 to 12 are flowcharts showing the basic operation of the air conditioner 5. The control device 50 of the air conditioner 5 starts operation by receiving a start signal from the remote controller 55 by the signal receiving unit 56 (step S101). Here, the CPU 57 of the control device 50 is activated. As will be described later, since the air conditioner 5 ends by switching the connection state of the coil 3 to the delta connection at the end of the previous operation, the connection state of the coil 3 becomes the delta connection at the start of operation (starting). ing.

Next, the control device 50 starts the air conditioner 5 (step S102). Specifically, for example, each fan motor of the indoor blower fan 47 and the outdoor blower fan 46 is driven.

Next, the control device 50 outputs a voltage switching signal to the converter 102, and boosts the bus voltage of the converter 102 to a bus voltage (for example, 390 V) corresponding to the delta connection (step S103). The bus voltage of the converter 102 is the maximum voltage applied from the inverter 103 to the motor 1.

Next, the control device 50 activates the electric motor 1 (step S104). As a result, in the electric motor 1, the connection state of the coil 3 is activated by the delta connection. Further, the control device 50 controls the output voltage of the inverter 103 to control the rotation speed of the electric motor 1.

Specifically, the control device 50 increases the rotation speed of the electric motor 1 stepwise at a predetermined speed according to the temperature difference ΔT. The maximum permissible rotation speed of the rotation speed of the electric motor 1 is, for example, 130 rps. As a result, the amount of refrigerant circulated by the compressor 41 is increased, the cooling capacity is increased in the case of cooling operation, and the heating capacity is increased in the case of heating operation.

Further, when the room temperature Ta approaches the set temperature Ts due to the air conditioning effect and the temperature difference ΔT shows a decreasing tendency, the control device 50 reduces the rotation speed of the electric motor 1 according to the temperature difference ΔT. When the temperature difference ΔT decreases to a predetermined near-zero temperature (however, greater than 0), the control device 50 operates the electric motor 1 at the minimum allowable rotation speed (for example, 20 rps).

Further, when the room temperature Ta reaches the set temperature Ts (that is, when the temperature difference ΔT becomes 0 or less), the control device 50 stops the rotation of the electric motor 1 to prevent overcooling (or overheating). To do. As a result, the compressor 41 is stopped. Then, when the temperature difference ΔT becomes larger than 0 again, the control device 50 restarts the rotation of the electric motor 1. The control device 50 regulates the resumption of rotation of the electric motor 1 in a short time so as not to repeat the rotation and the stop of the electric motor 1 in a short time.

Further, when the rotation speed of the electric motor 1 reaches a preset rotation speed, the inverter 103 weakens and starts field control. The field weakening control will be described later with reference to FIGS. 15 to 30.

The control device 50 determines whether or not an operation stop signal (operation stop signal of the air conditioner 5) has been received from the remote controller 55 via the signal receiving unit 56 (step S105). If the operation stop signal has not been received, the process proceeds to step S106. On the other hand, when the operation stop signal is received, the control device 50 proceeds to step S109.

The control device 50 acquires the temperature difference ΔT between the indoor temperature Ta detected by the indoor temperature sensor 54 and the set temperature Ts set by the remote controller 55 (step S106), and based on this temperature difference ΔT, the delta of the coil 3 Judge whether it is necessary to switch from the connection to the Y connection. That is, it is determined whether or not the connection state of the coil 3 is delta connection and the absolute value of the temperature difference ΔT is equal to or less than the threshold value ΔTr (step S107). The threshold value ΔTr is a temperature difference corresponding to an air conditioning load (also simply referred to as “load”) that is small enough to switch to Y connection.

As described above, ΔT is represented by ΔT = Ts-Ta when the operation mode is heating operation and ΔT = Ta-Ts when the operation mode is cooling operation. Therefore, here, the absolute value and threshold value of ΔT are expressed. The necessity of switching to the Y connection is determined by comparing with ΔTr.

As a result of comparison in step S107, if the connection state of the coil 3 is delta connection and the absolute value of the temperature difference ΔT is equal to or less than the threshold value ΔTr, the process proceeds to step S121 (FIG. 11).

As shown in FIG. 11, in step S121, the control device 50 outputs a stop signal to the inverter 103 to stop the rotation of the electric motor 1. After that, the control device 50 outputs a connection switching signal to the connection switching unit 60, and switches the connection state of the coil 3 from the delta connection to the Y connection (step S122). Subsequently, the control device 50 outputs a voltage switching signal to the converter 102, steps down the bus voltage of the converter 102 to a voltage (280 V) corresponding to the Y connection (step S123), and restarts the rotation of the motor 1 (step). S124). After that, the process returns to step S105 (FIG. 10) described above.

As a result of the comparison in step S107, when the connection state of the coil 3 is not delta connection (Y connection), or when the absolute value of the temperature difference ΔT is larger than the threshold value ΔTr (that is, it is not necessary to switch to Y connection). In the case), the process proceeds to step S108.

In step S108, it is determined whether or not it is necessary to switch from the Y connection to the delta connection. That is, it is determined whether or not the connection state of the coil 3 is Y connection and the absolute value of the temperature difference ΔT is larger than the threshold value ΔTr.

As a result of comparison in step S108, if the connection state of the coil 3 is Y connection and the absolute value of the temperature difference ΔT is larger than the threshold value ΔTr, the process proceeds to step S131 (FIG. 12).

As shown in FIG. 12, in step S131, the control device 50 stops the rotation of the electric motor 1. After that, the control device 50 outputs a connection switching signal to the connection switching unit 60, and switches the connection state of the coil 3 from Y connection to delta connection (step S132). Subsequently, the control device 50 outputs a voltage switching signal to the converter 102, boosts the bus voltage of the converter 102 to a voltage (390 V) corresponding to the delta connection (step S133), and restarts the rotation of the motor 1 (step). S134).

In the case of the delta connection, the motor 1 can be driven to a higher rotation speed than the Y connection, so that it can handle a larger load. Therefore, the temperature difference ΔT between the room temperature and the set temperature can be converged in a short time. After that, the process returns to step S105 (FIG. 10) described above.

As a result of the comparison in step S108, when the connection state of the coil 3 is not Y connection (delta connection), or when the absolute value of the temperature difference ΔT is equal to or less than the threshold value ΔTr (that is, it is necessary to switch to delta connection). If not), the process returns to step S105.

When the operation stop signal is received in step S105, the rotation of the electric motor 1 is stopped (step S109). After that, the control device 50 switches the connection state of the coil 3 from the Y connection to the delta connection (step S110). If the connection state of the coil 3 is already a delta connection, the connection state is maintained. Although omitted in FIG. 10, when the operation stop signal is received also between steps S106 and S108, the process proceeds to step S109 to stop the rotation of the electric motor 1.

After that, the control device 50 stops the air conditioner 5 (step S111). Specifically, each fan motor of the indoor blower fan 47 and the outdoor blower fan 46 is stopped. After that, the CPU 57 of the control device 50 is stopped, and the operation of the air conditioner 5 is completed.

As described above, when the absolute value of the temperature difference ΔT between the room temperature Ta and the set temperature Ts is relatively small (that is, when the threshold value is ΔTr or less), the motor 1 is operated with a highly efficient Y connection. Then, when it is necessary to handle a larger load, that is, when the absolute value of the temperature difference ΔT is larger than the threshold value ΔTr, the motor 1 is operated with a delta connection capable of handling a larger load. Therefore, the operating efficiency of the air conditioner 5 can be improved.

In the switching operation from the Y connection to the delta connection (FIG. 12), as shown in FIG. 13 (A), the rotation speed of the motor 1 is detected before the step S131 to stop the rotation of the motor 1 (step). S135), it may be determined whether or not the detected rotation speed is equal to or higher than the threshold value (reference value of the rotation speed) (step S136). The rotation speed of the electric motor 1 is detected as the frequency of the output current of the inverter 103.

In step S136, as the threshold value of the rotation speed of the electric motor 1, for example, 60 rps, which is between the rotation speed of 35 rps corresponding to the heating intermediate condition described later and the rotation speed of 85 rps corresponding to the heating rated condition, is used. If the rotation speed of the electric motor 1 is equal to or higher than the threshold value, the rotation of the electric motor 1 is stopped, the connection is switched to the delta connection, and the bus voltage of the converter 102 is boosted (steps S131, S132, S133). If the rotation speed of the electric motor 1 is less than the threshold value, the process returns to step S105 in FIG.

In this way, in addition to the determination of the necessity of connection switching based on the temperature difference ΔT (step S108), the determination of the necessity of connection switching based on the rotation speed of the motor 1 is performed, so that the connection switching is frequently repeated. It can be reliably suppressed.

Further, as shown in FIG. 13B, the output voltage of the inverter 103 is detected (step S137) before the step S131 of stopping the rotation of the electric motor 1, and the detected output voltage is the threshold value (reference value of the output voltage). ) Or not may be determined (step S138).

13 (A) and 13 (B) show the switching operation from the Y connection to the delta connection, but when switching from the delta connection to the Y connection, the judgment is based on the rotation speed of the motor 1 or the output voltage of the inverter 103. May be done.

FIG. 14 is a timing chart showing an example of the operation of the air conditioner 5. FIG. 14 shows the operating state of the air conditioner 5, and the driving state of the outdoor blower fan 46 and the electric motor 1 (compressor 41). The outdoor blower fan 46 is shown as an example of components other than the electric motor 1 of the air conditioner 5.

When the signal receiving unit 56 receives the operation start signal (ON command) from the remote controller 55, the CPU 57 is started and the air conditioner 5 is put into the start state (ON state). When the air conditioner 5 is in the activated state, the fan motor of the outdoor blower fan 46 starts rotating after the time t0 elapses. The time t0 is a delay time due to communication between the indoor unit 5A and the outdoor unit 5B.

After the time t1 elapses after the start of the air conditioner 5, the rotation of the electric motor 1 by the delta connection is started. The time t1 is a waiting time until the rotation of the fan motor of the outdoor blower fan 46 stabilizes. By rotating the outdoor blower fan 46 before the start of rotation of the electric motor 1, it is possible to prevent the temperature of the refrigeration cycle from rising more than necessary.

In the example of FIG. 14, the operation stop signal (OFF command) is received from the remote controller 55 after switching from the delta connection to the Y connection and further switching from the Y connection to the delta connection. The time t2 required for switching the connection is the waiting time required for restarting the electric motor 1, and is set to the time required for the refrigerant pressure in the refrigeration cycle to become substantially uniform.

When the operation stop signal is received from the remote controller 55, the rotation of the electric motor 1 is stopped, and then the rotation of the fan motor of the outdoor blower fan 46 is stopped after the time t3 has elapsed. The time t3 is a waiting time required to sufficiently lower the temperature of the refrigeration cycle. Then, after the time t4 elapses, the CPU 57 is stopped, and the air conditioner 5 is put into the operation stop state (OFF state). The time t4 is a preset waiting time.

<About connection switching based on temperature detection>
In the above operation of the air conditioner 5, the determination as to whether or not the connection state of the coil 3 needs to be switched (steps S107 and S108) can be determined based on, for example, the rotation speed of the electric motor 1 or the inverter output voltage. However, since the rotation speed of the electric motor 1 may fluctuate in a short time, it is necessary to determine whether or not the state in which the rotation speed is below the threshold value (or above the threshold value) continues for a certain period of time. The same applies to the inverter output voltage.

In particular, when the set temperature by the remote controller 55 is significantly changed, or when the load of the air conditioner 5 changes suddenly due to opening the window of the room, etc., it is necessary to switch the connection state of the coil 3. If it takes time to make a determination, the response of the operating state of the compressor 41 to the load fluctuation is delayed. As a result, the comfort of the air conditioner 5 may be reduced.

On the other hand, in this embodiment, the temperature difference ΔT (absolute value) between the indoor temperature Ta and the set temperature Ts detected by the indoor temperature sensor 54 is compared with the threshold value. Since the temperature does not fluctuate in a short time, it is not necessary to continue detecting the temperature difference ΔT and comparing it with the threshold value, and it is possible to determine whether or not the connection is switched in a short time. Therefore, the operating state of the compressor 41 can be quickly made to respond to load fluctuations, and the comfort of the air conditioner 5 can be improved.

In the operation of the air conditioner 5 described above, the determination of the necessity of switching from the delta connection to the Y connection (step S107) and the determination of the necessity of switching from the Y connection to the delta connection (step S108) are continued. However, the switching from delta connection to Y connection is performed when the air conditioning load is low (the room temperature is close to the set temperature), and then the air conditioning load suddenly increases. Since it is unlikely that this will happen, it is unlikely that the connections will be switched frequently.

Further, in the operation of the air conditioner 5 described above, the connection state of the coil 3 is switched (steps S122 and S132) in a state where the rotation of the electric motor 1 is stopped (that is, a state where the output of the inverter 103 is stopped). .. It is possible to switch the connection state of the coil 3 while continuing to supply power to the electric motor 1, but due to the simplicity of the reliability of the relay contacts constituting the switches 61, 62, 63 (FIG. 6) of the connection switching unit 60, It is desirable to switch while the power supply to the motor 1 is stopped.

It is also possible to switch the connection state of the coil 3 in a state where the rotation speed of the electric motor 1 is sufficiently lowered, and then return to the original rotation speed.

Further, here, the switches 61, 62, 63 of the connection switching unit 60 are composed of relay contacts, but when the switches 61, 62, 63 are composed of relay contacts, it is necessary to stop the rotation of the motor 1 when the connection state of the coil 3 is switched. There is no.

Further, when the state in which the temperature difference ΔT (absolute value) between the room temperature Ta and the set temperature Ts is equal to or less than the threshold value ΔTr is repeated a plurality of times (preset number of times), the connection state of the coil 3 may be switched. .. By doing so, it is possible to suppress repeated connection switching due to a small temperature change.

As described above, when the temperature difference ΔT between the room temperature and the set temperature becomes 0 or less (ΔT ≦ 0), the control device 50 stops the rotation of the electric motor 1 to prevent overcooling (or overheating). At this timing, the connection state of the coil 3 may be switched from the delta connection to the Y connection. Specifically, in step S107 described above, it is determined whether or not the temperature difference ΔT is 0 or less, and if the temperature difference ΔT is 0 or less, the rotation of the motor 1 is stopped and the connection state of the coil 3 is changed to Y. You can switch to the connection.

Further, in the operation of the air conditioner 5 described above, since the bus voltage of the converter 102 is boosted when switching from the Y connection to the delta connection, a higher torque can be generated by the electric motor 1. Therefore, the difference ΔT between the room temperature and the set temperature can be converged in a shorter time. The boosting of the bus voltage of the converter 102 will be described later.

<About the connection status at startup>
As described above, when the air conditioner 5 of the first embodiment receives the operation start signal and starts the electric motor 1, the control is started with the connection state of the coil 3 as the delta connection. Further, when the operation of the air conditioner 5 is stopped, the connection state of the coil 3 is switched to the delta connection.

At the start of operation of the air conditioner 5, it is difficult to accurately detect the air conditioning load. In particular, at the start of operation of the air conditioner 5, the difference between the room temperature and the set temperature is large, and the air conditioning load is generally large. Therefore, in the first embodiment, the electric motor 1 is started in a state where the connection state of the coil 3 is a delta connection that can handle a larger load (that is, can rotate to a higher rotation speed). As a result, at the start of operation of the air conditioner 5, the difference ΔT between the room temperature Ta and the set temperature Ts can be converged in a shorter time.

Further, even if the air conditioner 5 is stopped for a long period of time and an abnormality occurs in the connection switching unit 60 (for example, the relays of switches 61 to 63 are stuck and do not operate), the air conditioner 5 Since the Y connection is switched to the delta connection before the operation is stopped, the motor 1 can be started by the delta connection. Therefore, it is possible to prevent a decrease in the capacity of the air conditioner 5, and the comfort is not impaired.

When the motor 1 is started with the connection state of the coil 3 as the delta connection and the connection is not switched to the Y connection, the connection state of the coil is always the delta connection (there is no connection switching function). It is possible to obtain the same motor efficiency as that of a simple electric motor.

<Motor efficiency and motor torque>
Next, improvements in motor efficiency and motor torque will be described. In general, household air conditioners are subject to the Energy Conservation Law, and it is obligatory to reduce CO ₂ emissions from the viewpoint of the global environment. Advances in technology have improved the compression efficiency of compressors, the operating efficiency of compressor electric motors, the heat transfer rate of heat exchangers, etc., and the energy consumption efficiency COP (Coefficient of Performance) of air conditioners has improved year by year. Running costs (power consumption) and CO ₂ emissions are also reduced.

The COP evaluates the performance when operating under a certain temperature condition, and does not take into account the operating conditions of the air conditioner according to the season. However, in actual use of the air conditioner, changes in the outside air temperature change the capacity and power consumption required for cooling or heating. Therefore, in order to evaluate in a state close to the actual use, APF (Annual Performance Factor: annual energy consumption efficiency) that determines a certain model case, calculates the total load and total power consumption throughout the year, and obtains efficiency It is used as an index of energy saving.

In particular, in the current mainstream inverter electric motor, the capacity changes depending on the rotation speed of the compressor, so there is a problem in performing an evaluation close to actual use only under the rated conditions.

The APF of a household air conditioner calculates the power consumption according to the total annual load at five evaluation points of cooling rating, cooling intermediate, heating rating, heating intermediate, and heating low temperature. The larger this value is, the higher the energy saving is evaluated.

As for the breakdown of the total annual load, the ratio of intermediate heating conditions is very large (50%), followed by the ratio of rated heating conditions (25%). Therefore, improving the motor efficiency under the intermediate heating conditions and the rated heating conditions is effective in improving the energy saving of the air conditioner.

The number of revolutions of the compressor motor under the evaluation load condition of APF varies depending on the capacity of the air conditioner and the performance of the heat exchanger. For example, in a household air conditioner having a refrigerating capacity of 6.3 kW, the rotation speed N1 (first rotation speed) under the intermediate heating condition is 35 rps, and the rotation speed N2 (second rotation speed) under the heating rated condition. The number) is 85 rps.

The motor 1 of this embodiment is intended to obtain high motor efficiency and motor torque at a rotation speed N1 corresponding to a heating intermediate condition and a rotation speed N2 corresponding to a heating rated condition. That is, of the two load conditions for which performance is to be improved, the rotation speed on the low speed side is N1 and the rotation speed on the high speed side is N2.

In the electric motor 1 in which the permanent magnet 25 is mounted on the rotor 20, when the rotor 20 rotates, the magnetic flux of the permanent magnet 25 is interlinked with the coil 3 of the stator 10, and an induced voltage is generated in the coil 3. The induced voltage is proportional to the number of rotations (rotational speed) of the rotor 20 and also to the number of turns of the coil 3. The higher the rotation speed of the electric motor 1 and the larger the number of turns of the coil 3, the larger the induced voltage.

The line voltage (motor voltage) output from the inverter 103 is equal to the sum of the above-mentioned induced voltage and the voltage generated by the resistance and inductance of the coil 3. Since the resistance and inductance of the coil 3 are negligibly small compared to the induced voltage, the line voltage is effectively dominated by the induced voltage. Further, the magnet torque of the electric motor 1 is proportional to the product of the induced voltage and the current flowing through the coil 3.

The induced voltage increases as the number of turns of the coil 3 increases. Therefore, the larger the number of turns of the coil 3, the smaller the current for generating the required magnet torque. As a result, the loss due to the energization of the inverter 103 can be reduced, and the operating efficiency of the electric motor 1 can be improved. On the other hand, due to the rise in the induced voltage, the line voltage controlled by the induced voltage reaches the inverter maximum output voltage (that is, the bus voltage supplied from the converter 102 to the inverter 103) at a lower rotation speed, and the rotation speed is increased. It can't be faster than that.

Further, when the number of turns of the coil 3 is reduced, the induced voltage is lowered, so that the line voltage controlled by the induced voltage does not reach the maximum output voltage of the inverter up to a higher rotation speed, and high-speed rotation becomes possible. However, as the induced voltage decreases, the current for generating the required magnet torque increases, so that the loss due to the energization of the inverter 103 increases, and the operating efficiency of the electric motor 1 decreases.

Further, from the viewpoint of the switching frequency of the inverter 103, when the line voltage is closer to the maximum output voltage of the inverter, the harmonic component due to the ON / OFF duty of the switching of the inverter 103 decreases, so that the harmonic component of the current becomes The resulting iron loss can be reduced.

15 and 16 are graphs showing the relationship between the line voltage and the rotation speed in the electric motor 1. The connection state of the coil 3 is Y connection. The line voltage is proportional to the product of the field magnetic field and the rotation speed. If the field magnetic field is constant, the line voltage and the rotation speed are proportional to each other, as shown in FIG. In FIG. 15, the rotation speed N1 corresponds to the heating intermediate condition, and the rotation speed N2 corresponds to the heating rated condition.

The line voltage also increases as the rotation speed increases, but as shown in FIG. 16, when the line voltage reaches the maximum output voltage of the inverter, the line voltage cannot be further increased, so that the field weakening control by the inverter 103 is performed. Is started. Here, it is assumed that the field weakening control is started at the rotation speed between the rotation speeds N1 and N2.

In field weakening control, the induced voltage is weakened by passing a current in the d-axis phase (direction that cancels the magnetic flux of the permanent magnet 25) through the coil 3. This current is called a weakening current. Since it is necessary to pass a weakening current in addition to the current for generating the normal motor torque, the copper loss due to the resistance of the coil 3 increases, and the energization loss of the inverter 103 also increases.

FIG. 17 is a graph showing the relationship between the motor efficiency and the rotation speed when the field weakening control shown in FIG. 16 is performed. As shown in FIG. 17, the motor efficiency increases with the rotation speed, and the motor efficiency reaches its peak as shown by the arrow P immediately after the field weakening control is started.

When the rotation speed is further increased, the weakening current flowing through the coil 3 also increases, so that the copper loss due to this increases and the motor efficiency decreases. The total efficiency, which is the product of the motor efficiency and the inverter efficiency, also shows a change represented by a curve similar to that in FIG.

FIG. 18 is a graph showing the relationship between the maximum torque and the rotation speed of the electric motor when the field weakening control shown in FIG. 16 is performed. Before starting field weakening control, the maximum torque of the motor is constant (eg, due to current threshold constraints). When the field weakening control is started, the maximum torque of the motor 1 decreases as the rotation speed increases. The maximum torque of the electric motor 1 is set to be larger than the load actually generated (required load) of the electric motor 1 when the product is used. Hereinafter, for convenience of explanation, the maximum torque of the electric motor will be referred to as an electric motor torque.

FIG. 19 is a graph showing the relationship between the line voltage and the rotation speed for each of the Y connection and the delta connection. When the connection state of the coil 3 is a delta connection, the phase impedance of the coil 3 is 1 / √3 times that when the connection state of the coil 3 is a Y connection, assuming that the number of turns is the same. Therefore, the line voltage (dashed line) when the connection state of the coil 3 is delta connection is 1 of the line voltage (solid line) when the connection state of the coil 3 is Y connection, assuming that the rotation speed is the same. / √ 3 times.

That is, when the coil 3 is connected by delta connection, if the number of turns is √3 times that of the Y connection, the line voltage (motor voltage) becomes equivalent to the case of Y connection for the same rotation number N. Therefore, the output current of the inverter 103 is also equivalent to the case of Y connection.

In an electric motor in which the number of turns to the teeth is several tens or more, Y connection is often adopted rather than delta connection for the following reasons. One is that the delta connection has a larger number of coil turns than the Y connection, so that the time required for winding the coil in the manufacturing process becomes longer. Another reason is that circulating current can occur in the case of delta connections.

Generally, in an electric motor that employs a Y connection, the line voltage (motor voltage) reaches the inverter maximum output voltage at the rotation speed N2 (that is, the rotation speed on the high-speed side among the rotation speeds for which performance is to be improved). In addition, the number of coil turns is adjusted. However, in this case, at the rotation speed N1 (that is, the rotation speed on the low speed side among the rotation speeds targeted for performance improvement), the electric motor is operated in a state where the line voltage is lower than the maximum output voltage of the inverter. It is difficult to obtain high motor efficiency.

Therefore, the connection state of the coil is set to Y connection, the number of turns is adjusted so that the line voltage reaches the maximum output voltage of the inverter at a rotation speed slightly lower than the rotation speed N1, and the number of turns is adjusted until the rotation speed N2 is reached. , The control is performed to switch the connection state of the coil to the delta connection.

FIG. 20 is a graph showing the relationship between the line voltage and the rotation speed when switching from the Y connection to the delta connection. In the example shown in FIG. 20, when the rotation speed (referred to as the rotation speed N11) is slightly lower than the rotation speed N1 (heating intermediate condition) is reached, the field weakening control described above is started. When the rotation speed N further increases and reaches the rotation speed N0, the Y connection is switched to the delta connection. The rotation speed N11 here is a rotation speed 5% lower than the rotation speed N1 (that is, N11 = N1 × 0.95).

By switching to the delta connection, the line voltage drops to 1 / √3 times that of the Y connection, so that the degree of field weakening can be kept small (that is, the weakening current can be made small). As a result, copper loss due to the weakening current can be suppressed, and a decrease in motor efficiency and motor torque can be suppressed.

FIG. 21 is a graph showing the relationship between the motor efficiency and the rotation speed for each of the Y connection and the delta connection. As described above, the connection state of the coil 3 is set to Y connection, and the number of turns is adjusted so that the line voltage reaches the maximum output voltage of the inverter at the rotation speed N11 slightly lower than the rotation speed N1. As shown by the solid line, high motor efficiency can be obtained at the rotation speed N1.

On the other hand, assuming that the number of turns of the coil 3 is the same, in the case of the delta connection, as shown by the alternate long and short dash line in FIG. 21, the motor efficiency is higher at the rotation speed N2 than in the case of the Y connection. Therefore, if the Y connection is switched to the delta connection at the intersection of the solid line and the one-point chain line shown in FIG. 21, high motor efficiency can be obtained at both the rotation speed N1 (heating intermediate condition) and the rotation speed N2 (heating rated condition).

Therefore, as described with reference to FIG. 20, the connection state of the coil 3 is defined as Y connection, and the line voltage becomes the maximum output voltage of the inverter when the rotation speed is N11 (the rotation speed is slightly lower than the rotation speed N1). The number of turns is adjusted so as to reach it, and control is performed to switch from Y connection to delta connection at a rotation speed N0 higher than the rotation speed N1.

However, simply switching the connection state of the coil 3 from the Y connection to the delta connection cannot sufficiently improve the motor efficiency. This point will be described below.

In FIG. 22, the connection state of the coil 3 is set to Y connection, the number of turns is adjusted so that the line voltage reaches the maximum output voltage of the inverter at the rotation speed N11, and the Y connection is switched to the delta connection at the rotation speed N0. It is a graph which shows the relationship between the motor efficiency of the case (solid line), and the rotation speed. As shown in FIG. 17, the broken line is a graph showing the relationship between the motor efficiency and the rotation speed when the connection state of the coil 3 is Y connection and field weakening control is performed.

The line voltage is proportional to the number of revolutions. For example, in a household air conditioner having a refrigerating capacity of 6.3 kW, the rotation speed N1 (heating intermediate condition) is 35 rps and the rotation speed N2 (heating rated condition) is 85 rps, so that the line voltage in the heating intermediate condition is As a reference, the line voltage under the heating rated condition is 2.4 times (= 85/35).

After switching the connection state of the coil 3 to the delta connection, the line voltage under the heating rated condition (rotation speed N2) is 1.4 times (= 85/35 / √3) the maximum output voltage of the inverter. .. Since the line voltage cannot be made larger than the maximum output voltage of the inverter, field weakening control is started.

In the field weakening control, the weakening current required to weaken the field is passed through the coil 3, so that the copper loss increases and the motor efficiency and the motor torque decrease. Therefore, as shown by the solid line in FIG. 22, the motor efficiency under the heating rated condition (rotation speed N2) cannot be improved.

In order to suppress the degree of field weakening under the heating rated condition (rotation speed N2) (reduce the weakening current), it is necessary to reduce the number of turns of the coil 3 to lower the line voltage. The line voltage under the intermediate heating condition (rotation speed N1) also decreases, and the effect of improving the motor efficiency by switching the connection becomes small.

That is, when there are two load conditions for which the performance is to be improved, and the rotation speed N1 on the low speed side and the rotation speed N2 on the high speed side satisfy (N2 / N1)> √3, the Y connection is used. Even if the connection is switched to the delta connection, field weakening control is required. Therefore, simply switching from the Y connection to the delta connection cannot obtain a sufficient effect of improving the motor efficiency.

FIG. 23 is a graph showing the relationship between the motor torque and the rotation speed for each of the Y connection and the delta connection. In the case of the Y connection, as described with reference to FIG. 18, the motor torque is constant with respect to the increase in the rotation speed N, but when the field weakening control is started, the motor torque increases as the rotation speed N increases. Decreases. In the case of the delta connection, the field weakening control is started at a higher rotation speed than in the case of the Y connection (N11), but when the field weakening control is started, the motor torque decreases as the rotation speed N increases.

In FIG. 24, the connection state of the coil 3 is Y connection, and the number of turns is adjusted so that the line voltage reaches the maximum output voltage of the inverter when the rotation speed is N11 (the rotation speed is slightly lower than the rotation speed N1). It is a graph which shows the relationship between the motor torque and the rotation speed at the time of switching from the Y connection to the delta connection at the rotation speed N0 which is higher than the rotation speed N1. As shown in FIG. 24, when the rotation speed reaches the rotation speed N11 and the field weakening control is started, the motor torque decreases as the rotation speed N increases.

When the rotation speed further increases and reaches the rotation speed N0 and the Y connection is switched to the delta connection, the field weakening control is temporarily stopped, so that the motor torque increases. However, when the rotation speed N is further increased and the field weakening control is started, the motor torque decreases as the rotation speed N increases. As described above, simply switching from the Y connection to the delta connection cannot suppress the decrease in the motor torque especially in the high rotation speed range.

Therefore, in the drive device 100 of the first embodiment, in addition to switching the connection state of the coil 3 by the connection switching unit 60, the bus voltage is switched by the converter 102. The converter 102 is supplied with a power supply voltage (200V) from the power supply 101, and supplies a bus voltage to the inverter 103. It is desirable that the converter 102 is composed of an element having a small loss due to a voltage rise (boost), for example, a SiC element or a GaN element.

Specifically, the bus voltage V1 (first bus voltage) when the connection state of the coil 3 is Y connection is set to 280 V (DC). On the other hand, the bus voltage V2 (second bus voltage) when the connection state of the coil 3 is a delta connection is set to 390 V (DC). That is, the bus voltage V2 in the case of delta connection is set to 1.4 times the bus voltage V1 in the case of Y connection. The bus voltage V2 may be V2 ≧ (V1 / √3) × N2 / N1 with respect to the bus voltage V1. The inverter 103 to which the bus voltage is supplied from the converter 102 supplies the line voltage to the coil 3. The maximum output voltage of the inverter is 1 / √2 of the bus voltage.

FIG. 25 is a graph showing the relationship between the line voltage and the rotation speed when the bus voltage is switched by the converter 102 for each of the Y connection and the delta connection. As shown in FIG. 25, the line voltage (solid line) when the connection state of the coil 3 is Y connection is 1 / √2 (that is, V1 × 1 / √2) of the bus voltage V1 at the maximum. When the connection state of the coil 3 is delta connection, the line voltage (dashed line) is 1 / √2 (that is, V2 × 1 / √2) of the bus voltage V2 at the maximum.

FIG. 26 is a graph showing the relationship between the line voltage and the rotation speed when the connection state is switched by the connection switching unit 60 and the bus voltage is switched by the converter 102. As shown in FIG. 26, in the rotation speed range including the rotation speed N1 (heating intermediate condition), the connection state of the coil 3 is Y connection. The line voltage increases with the increase in the rotation speed, and the line voltage reaches the maximum output of the inverter (V1 × 1 / √2) at the rotation speed N11 slightly lower than the rotation speed N1. As a result, field weakening control is started.

When the rotation speed further increases and reaches the rotation speed N0, the connection switching unit 60 switches the connection state of the coil 3 from the Y connection to the delta connection. At the same time, the converter 102 boosts the bus voltage from V1 to V2. By boosting, the maximum output of the inverter becomes V2 × 1 / √2. At this point, since the line voltage is lower than the maximum output of the inverter, field weakening control is not performed.

After that, the line voltage increases as the rotation speed N increases, and the line voltage reaches the maximum inverter output (V2 × 1 / √2) at the rotation speed N21, which is slightly lower than the rotation speed N2 (heating rated condition). As a result, field weakening control is started. The rotation speed N21 is a rotation speed 5% lower than the rotation speed N2 (that is, N21 = N2 × 0.95).

In the first embodiment, as described above, the connection state of the coil 3 is switched based on the comparison result between the temperature difference ΔT between the room temperature Ta and the set temperature Ts and the threshold value ΔTr. The switching from the Y connection to the delta connection at the rotation speed N0 corresponds to the switching from the Y connection to the delta connection shown in steps S108 of FIG. 10 and steps S131 to S134 of FIG.

The effect of improving the motor efficiency in this case will be described. FIG. 27 is a graph showing the relationship between the motor efficiency and the rotation speed for each of the Y connection and the delta connection. In FIG. 27, the motor efficiency (solid line) when the connection state of the coil 3 is Y connection is the same as the motor efficiency in Y connection shown in FIG. On the other hand, the motor efficiency (dashed line) when the connection state of the coil 3 is delta connection is higher than the motor efficiency in delta connection shown in FIG. 21 because the bus voltage of the converter 102 rises.

FIG. 28 is a graph showing the relationship between the motor efficiency and the rotation speed when the connection state is switched by the connection switching unit 60 and the bus voltage is switched by the converter 102. The connection state of the coil 3 is Y connection, and the number of turns is set so that the line voltage reaches the maximum output voltage of the inverter when the rotation speed is N11 (the rotation speed is slightly lower than the rotation speed N1). High motor efficiency can be obtained in the rotation speed range including the number N1.

When the rotation speed reaches the above rotation speed N11, field weakening control is started, and when the rotation speed reaches N0, the connection state of the coil 3 is switched from Y connection to delta connection, and the bus voltage is increased by the converter 102. To do.

Since the maximum output voltage of the inverter also rises as the bus voltage rises, the line voltage becomes lower than the maximum output voltage of the inverter, and as a result, the field weakening control is stopped. By stopping the field weakening control, the copper loss caused by the weakening current is reduced, so that the motor efficiency is increased.

Further, when the rotation speed N reaches the rotation speed N21 which is slightly smaller than the rotation speed N2 (heating rated condition), the line voltage reaches the maximum output voltage of the inverter, and the field weakening control is started. Although the copper loss increases with the start of field weakening control, high motor efficiency can be obtained because the bus voltage is increased by the converter 102.

That is, as shown by the solid line in FIG. 28, high motor efficiency can be obtained at both the rotation speed N1 (heating intermediate condition) and the rotation speed N2 (heating rated condition).

Next, the effect of improving the motor torque will be described. FIG. 29 is a graph showing the relationship between the motor torque and the rotation speed for each of the case where the connection state of the coil 3 is Y connection and the case where the coil 3 is delta connection. The motor torque (solid line) in the case of Y connection is the same as in FIG. In the case of delta connection, the motor torque (single point chain wire) decreases as the rotation speed N increases when the field weakening control is started at the rotation speed N21 slightly lower than the rotation speed N2 (heating rated condition).

In FIG. 30, the connection state of the coil 3 is defined as Y connection, the number of turns is adjusted so that the line voltage reaches the maximum output voltage of the inverter when the rotation speed is N11, and the Y connection is delta at the rotation speed N0 (> N1). It is a graph which shows the relationship between the motor torque and the number of rotations at the time of switching to a connection and further boosting the bus voltage. As shown in FIG. 30, when the field weakening control is started at the rotation speed N11 slightly lower than the rotation speed N1 (heating intermediate condition), the motor torque decreases as the rotation speed N increases.

When the rotation speed N further increases and reaches the rotation speed N0, the connection state of the coil 3 is switched from the Y connection to the delta connection, and the bus voltage further rises. Due to the switch to the delta connection and the rise in the bus voltage, the line voltage becomes lower than the maximum output voltage of the inverter, so the field weakening control stops. As a result, the motor torque increases. After that, when the field weakening control is started at the rotation speed N21 slightly lower than the rotation speed N2 (heating rated condition), the motor torque decreases as the rotation speed N increases.

In this way, after switching to the delta connection, field weakening control is not performed until the rotation speed N reaches the rotation speed N21 (the rotation speed slightly smaller than the rotation speed N2), so that the rotation speed N2 (heating rated condition) is particularly high. ) Is included in the rotation speed range, and the decrease in motor torque can be suppressed.

That is, as shown by the solid line in FIG. 30, high motor torque can be obtained at both the rotation speed N1 (heating intermediate condition) and the rotation speed N2 (heating rated condition). That is, high performance (motor efficiency and motor torque) can be obtained in both the heating intermediate condition and the heating rated condition of the air conditioner 5.

When the voltage of the converter 102 is boosted, a loss is generated due to the boosting. Therefore, in the connection state (that is, Y connection) under the heating intermediate condition having the largest contribution to the motor efficiency, the power supply voltage is used without boosting. It is preferable to do so. The power supply voltage of the power supply 101 is 200V (effective value), and the maximum value is 280V (= 200V × √2). Therefore, it can be said that the bus voltage (280V) of the converter 102 in the case of Y connection is the same as the maximum value of the power supply voltage.

Further, the switching of the bus voltage supplied to the inverter 103 may be performed by stepping up or lowering the power supply voltage.

Further, in the operation control of the air conditioner 5 described above, the Y connection is made at the rotation speed N1 (heating intermediate condition) and the delta connection is made at the rotation speed N2 (heating rated condition), but the specific load condition is not determined. In this case, the voltage level may be adjusted by setting the rotation speed N1 as the maximum rotation speed for operating in the Y connection and the rotation speed N2 as the maximum rotation speed for operating in the delta connection. Even with this control, the efficiency of the electric motor 1 can be improved.

As described above, in the household air conditioner 5, the efficiency of the electric motor 1 can be improved by setting the rotation speed N1 as the rotation speed under the heating intermediate condition and the rotation speed N2 as the rotation speed under the heating rated condition. it can.

<Effect of Embodiment 1>
As described above, in the first embodiment, since the converter 102 changes the magnitude of the bus voltage according to the switching of the connection state of the coil 3 by the connection switching unit 60, either before or after the switching of the connection state. Also, high motor efficiency and high motor torque can be obtained.

Further, since the connection state of the coil 3 is switched between the Y connection (first connection state) and the delta connection (second connection state) in which the line voltage is lower than that of the first connection state, the operation of the motor 1 is performed. The connection state suitable for the state can be selected.

Further, in the first embodiment, when the connection state of the coil 3 is the first connection state, the bus voltage of the converter 102 is set to the first bus voltage V1, and the connection state of the coil 3 is the second connection state. Occasionally, the bus voltage of the converter 102 is set to the second bus voltage V2, which is higher than the first bus voltage V1. Therefore, when the rotation speed of the motor 1 is high, it is possible to switch to the second connection state in which the line voltage is low, and further increase the bus voltage to improve the motor efficiency and the motor torque.

Further, when the first connection state is Y connection and the second connection state is delta connection, and the first rotation speed N1 and the second rotation speed N2 of the motor 1 satisfy N2 / N1> √3. When the rotation speed of the motor 1 is the first rotation speed N1, the connection state of the coil 3 is Y connection, and when the rotation speed of the motor 1 is the second rotation speed N2, the connection state of the coil 3 is set. Is a delta connection, so that the motor efficiency and the motor torque can be improved at any of the rotation speeds N1 and N2.

In particular, the first bus voltage V1, the second bus voltage V2, the first rotation speed N1 and the second rotation speed N2 rotate by satisfying V2 ≧ (V1 / √3) × N2 / N1. High motor efficiency and motor torque can be obtained in the numbers N1 and N2.

Further, since the first rotation speed N1 is the rotation speed corresponding to the heating intermediate condition and the second rotation speed N2 is the rotation speed corresponding to the heating rated condition, the heating intermediate condition and the heating subject to the performance improvement are targeted. High motor efficiency and motor torque can be obtained under the rated conditions.

That is, the first rotation speed N1 is the rotation speed corresponding to the operating condition having the highest ratio in the year-round energy consumption efficiency (APF), and the second rotation speed N2 is the operation having the second highest ratio in the year-round energy consumption efficiency (APF). Since the number of revolutions corresponds to the conditions, the effect of improving the energy consumption efficiency of the air conditioner is great.

Further, since the first bus voltage V1 is the same as √2 times the effective value of the power supply voltage, the converter 102 can be used without boosting the power supply voltage when the coil 3 is in the first connection state. And energy efficiency can be improved.

Further, since the converter 102 is composed of a SiC element or a GaN element, the loss due to boosting is small, and the energy efficiency can be further improved.

Further, in each of the Y connection (first connection state) and the delta connection (second connection state), the field weakening control is performed according to the rotation speed of the motor 1, so that the line voltage reaches the maximum output voltage of the inverter. Can also increase the rotation speed of the electric motor 1.

Further, when the control device 50 receives the operation stop signal from the remote control 55 via the signal receiving unit 56, the control device 50 is the air conditioner 5 after the connection state of the coil 3 is switched from the Y connection to the delta connection. End the operation. If the connection state of the coil 3 is already a delta connection, the connection state is maintained. Therefore, at the start of operation (starting) of the air conditioner 5, the operation of the air conditioner 5 can be started with the connection state of the coil 3 being delta connection. As a result, even when the temperature difference ΔT between the room temperature Ta and the set temperature Ts is large, the operation of the air conditioner 5 can be started in the state of the delta connection, and the room temperature Ta can be quickly brought close to the set temperature Ts. Can be done.

First modification.
Next, a first modification of the first embodiment will be described. In the first embodiment described above, the rotation speed N0 (that is, the rotation speed when the temperature difference ΔT and the threshold value ΔTr are the same) for switching the connection state of the coil from the Y connection to the delta connection and the delta connection to the Y connection The number of rotations to be switched N0 (temperature difference) was the same, but the number of rotations may be different.

31 (A) and 31 (B) are graphs showing the relationship between the motor efficiency and the rotation speed when the connection state is switched by the connection switching unit 60 and the bus voltage is switched by the converter 102. As shown in FIGS. 31A and 31B, the rotation speed N4 for switching the connection state of the coil 3 from the Y connection to the delta connection and the rotation speed N5 for switching the connection state from the delta connection to the Y connection are different from each other.

Further, the switching of the bus voltage by the converter 102 is performed at the same time as the switching of the connection state of the coil 3. That is, at the rotation speed N4 for switching from the Y connection to the delta connection, the bus voltage is boosted. On the other hand, at the rotation speed N5 for switching from the delta connection to the Y connection, the bus voltage is stepped down.

Such control can be executed, for example, by setting the threshold value ΔTr in step S107 of FIG. 10 and the threshold value ΔTr in step S108 to different values. In the examples shown in FIGS. 31A and 31B, the rotation speed N4 for switching from the Y connection to the delta connection is larger than the rotation speed N5 for switching from the delta connection to the Y connection, but the magnitude may be reversed. .. Other operations and configurations in the first modification are the same as in the first embodiment.

Also in this first modification, the operating state of the compressor 41 can be quickly made to respond to a sudden load fluctuation of the air conditioner 5 by switching the connection state of the coil 3 based on the room temperature Ta. Can be done. Further, high motor efficiency can be obtained by switching the bus voltage of the converter 102 according to the switching of the connection state of the coil 3.

Second modification.
Next, a second modification of the first embodiment will be described. In the above-described first embodiment, the bus voltage of the converter 102 is switched in two stages (V1 / V2), but as shown in FIG. 32, it may be switched in three stages.

FIG. 32 is a graph showing the relationship between the line voltage and the rotation speed when the connection state is switched and the bus voltage of the converter 102 is switched in the second modification. In the example of FIG. 32, in the rotation speed N1 (Y connection) corresponding to the heating intermediate condition, the bus voltage of the converter 102 is V1, and the rotation speed N6 between the rotation speed N1 and the rotation speed N2 (heating rated condition). The Y connection is switched to the delta connection, and at the same time, the bus voltage is boosted to V2.

Further, at the rotation speed N7 higher than the rotation speed N2, the bus voltage of the converter 102 is boosted to V3 while the connection state remains the same. From this rotation speed N7 to the maximum rotation speed N8, the bus voltage of the converter 102 is V3. Other operations and configurations in the second modification are the same as in the first embodiment.

As described above, in the second modification, since the bus voltage of the converter 102 is switched to three stages of V1, V2, and V3, high motor efficiency and high motor torque can be obtained particularly in a high rotation speed range. ..

The switching of the bus voltage is not limited to two or three steps, and may be four or more steps. Further, in the first modification (FIG. 31), the bus voltage of the converter 102 may be switched to three or more stages.

Third modified example.
Next, a third modification of the first embodiment will be described. In the first embodiment described above, the connection state of the coil 3 is switched between Y connection and delta connection. However, the connection state of the coil 3 may be switched between series connection and parallel connection.

33 (A) and 33 (B) are schematic views for explaining switching of the connection state of the coil 3 of the third modification. In FIG. 33 (A), the three-phase coils 3U, 3V, and 3W are connected by Y connection. Further, the coil portions Ua, Ub, Uc of the coil 3U are connected in series, the coil portions Va, Vb, Vc of the coil 3V are connected in series, and the coil portions Wa, Wb, Wc of the coil 3W are connected in series. There is. That is, the coil portions of each phase of the coil 3 are connected in series.

On the other hand, in FIG. 33B, the three-phase coils 3U, 3V, and 3W are connected by Y connection, but the coil portions Ua, Ub, and Uc of the coil 3U are connected in parallel, and the coil portion Va of the coil 3V. , Vb, Vc are connected in parallel, and the coil portions Wa, Wb, Wc of the coil 3W are connected in parallel. That is, the coil portions of each phase of the coil 3 are connected in parallel. The switching of the connection state of the coil 3 shown in FIGS. 33 (A) and 33 (B) can be realized, for example, by providing a changeover switch in each coil portion of the coil 3U, 3V, and 3W.

Assuming that the number of coil portions (that is, the number of rows) connected in parallel in each phase is n, the line voltage is 1 by switching from the series connection (FIG. 33 (A)) to the parallel connection (FIG. 33 (B)). / N times lower. Therefore, when the line voltage approaches the maximum output voltage of the inverter, the degree of field weakening can be suppressed to a small level (that is, the weakening current can be reduced) by switching the connection state of the coil 3 from series connection to parallel connection. it can.

When there are two load conditions for performance improvement, and the rotation speed N1 on the low speed side and the rotation speed N2 on the high speed side satisfy (N2 / N1)> n, the connection state of the coil 3 is changed. Since the line voltage becomes larger than the maximum output voltage of the inverter just by switching from the series connection to the parallel connection, field weakening control is required. Therefore, as described in the first embodiment, the connection state of the coil 3 is switched from the series connection to the parallel connection, and at the same time, the bus voltage of the converter 102 is boosted. As a result, high motor efficiency and high motor torque can be obtained in both the rotation speed range including the rotation speed N1 and the rotation speed range including the rotation speed N2.

34 (A) and 34 (B) are schematic views for explaining another configuration example of the third modification. In FIG. 34 (A), the three-phase coils 3U, 3V, and 3W are connected by delta connection. Further, the coil portions Ua, Ub, Uc of the coil 3U are connected in series, the coil portions Va, Vb, Vc of the coil 3V are connected in series, and the coil portions Wa, Wb, Wc of the coil 3W are connected in series. There is. That is, the coil portions of each phase of the coil 3 are connected in series.

On the other hand, in FIG. 34 (B), the three-phase coils 3U, 3V, and 3W are connected by delta connection, but the coil portions Ua, Ub, and Uc of the coil 3U are connected in parallel, and the coil portion Va of the coil 3V. , Vb, Vc are connected in parallel, and the coil portions Wa, Wb, Wc of the coil 3W are connected in parallel. That is, the coil portions of each phase of the coil 3 are connected in parallel.

In this case as well, as in the examples shown in FIGS. 33A and 33B, of the two load conditions for which the performance is to be improved, the rotation speed N1 on the low speed side and the rotation speed N2 on the high speed side are ( When N2 / N1)> n is satisfied, the connection state of the coil 3 is switched from the series connection (FIG. 33 (A)) to the parallel connection (FIG. 33 (B)), and at the same time, the bus voltage of the converter 102 is boosted. Other operations and configurations in the third modification are the same as in the first embodiment. The bus voltage V2 after boosting may be V2 ≧ (V1 / n) × N2 / N1 with respect to the bus voltage V1 before boosting.

As described above, in the third modification, the degree of field weakening can be suppressed to a small level and the motor efficiency can be improved by switching the connection state of the converter 102 between series connection and parallel connection. Further, when the bus voltages V1 and V2 and the rotation speeds N1 and N2 satisfy V2 ≧ (V1 / n) × N2 / N1, high motor efficiency and motor torque can be obtained at the rotation speeds N1 and N2.

In the first modification and the second modification, the series connection (first connection state) and the parallel connection (second connection state) may be switched.

Fourth modified example.
In the first embodiment described above, the absolute value of the difference ΔT between the indoor temperature Ta and the set temperature Ts detected by the indoor temperature sensor 54 is compared with the threshold value ΔTr, and the connection state of the coil 3 and the bus voltage of the converter 102 are switched. However, the air conditioning load may be calculated based on the room temperature Ta, and the connection state of the coil 3 and the bus voltage of the converter 102 may be switched based on the air conditioning load.

FIG. 35 is a flowchart showing the basic operation of the air conditioner of the fourth modification. Steps S101 to S105 are the same as those in the first embodiment. If the operation stop signal is not received after starting the electric motor 1 in step S104 (step S105), the control device 50 has the room temperature Ta detected by the room temperature sensor 54 and the set temperature Ts set by the remote control 55. The temperature difference ΔT with and from is acquired (step S201), and the air conditioning load is calculated based on this temperature difference ΔT (step S202).

Next, based on the calculated air conditioning load, it is determined whether or not it is necessary to switch the coil 3 from the delta connection to the Y connection. That is, it is determined whether or not the connection state of the coil 3 is delta connection and the air conditioning load calculated in step S202 is equal to or less than the threshold value (reference value of the air conditioning load) (step S203).

As a result of comparison in step S203, if the connection state of the coil 3 is delta connection and the air conditioning load is equal to or less than the threshold value, the processes of steps S121 to S124 shown in FIG. 11 are performed. In steps S121 to S124 of FIG. 11, as described in the first embodiment, switching from the delta connection to the Y connection and boosting the bus voltage by the converter 102 are performed.

As a result of the comparison in step S203, when the connection state of the coil 3 is not delta connection (Y connection), or when the air conditioning load is larger than the threshold value (that is, it is not necessary to switch to Y connection), The process proceeds to step S204.

In step S204, it is determined whether or not it is necessary to switch from the Y connection to the delta connection. That is, it is determined whether or not the connection state of the coil 3 is Y connection and the air conditioning load calculated in step S202 is larger than the threshold value.

As a result of the comparison in step S204, if the connection state of the coil 3 is Y connection and the air conditioning load is larger than the threshold value, the processes of steps S131 to S134 shown in FIG. 12 are performed. In steps S131 to S134 of FIG. 12, as described in the first embodiment, switching from the Y connection to the delta connection and lowering the bus voltage by the converter 102 are performed.

As a result of the comparison in step S204, when the connection state of the coil 3 is not Y connection (when it is delta connection), or when the air conditioning load is larger than the threshold value (that is, when it is not necessary to switch to delta connection), Return to step S105. The processing (steps S109 to S111) when the operation stop signal is received is the same as that of the first embodiment. Other operations and configurations in the fourth modification are the same as in the first embodiment.

As described above, in the fourth modification, the air conditioning load is calculated based on the room temperature Ta, and the connection state of the coil 3 and the bus voltage of the converter 102 are switched based on the calculated air conditioning load. The operating state of the compressor 41 can be quickly made to respond to the load fluctuation of 5, and the comfort can be improved.

In the first modification, the second modification, and the third modification, the connection state of the coil 3 and the bus voltage of the converter 102 may be switched based on the air conditioning load.

Fifth modification example.
In the first embodiment described above, the connection state of the coil 3 and the bus voltage of the converter 102 are switched based on the temperature difference ΔT between the indoor temperature Ta and the set temperature Ts detected by the indoor temperature sensor 54, but the rotation of the electric motor 1 The connection state of the coil 3 and the bus voltage of the converter 102 may be switched based on the number.

FIG. 36 is a flowchart showing the basic operation of the air conditioner of the fifth modification. Steps S101 to S105 are the same as those in the first embodiment. After starting the electric motor 1 in step S104, if the operation stop signal is not received (step S105), the control device 50 acquires the rotation speed of the electric motor 1 (step S301). The rotation speed of the electric motor 1 is the frequency of the output current of the inverter 103, and can be detected by using a current sensor or the like attached to the electric motor 1.

Next, based on the rotation speed of the electric motor 1, it is determined whether or not it is necessary to switch the coil 3 from the delta connection to the Y connection. That is, it is determined whether or not the connection state of the coil 3 is delta connection and the rotation speed of the electric motor 1 is equal to or less than the threshold value (reference value of the rotation speed) (step S302).

In the case of heating operation, the threshold value used in step S302 is preferably a value (more preferably, an intermediate value) between the rotation speed N1 corresponding to the heating intermediate condition and the rotation speed N2 corresponding to the heating rated condition. Further, in the case of cooling operation, the threshold value used in step S302 may be a value (more preferably an intermediate value) between the rotation speed N1 corresponding to the cooling intermediate condition and the rotation speed N2 corresponding to the cooling rated condition. desirable.

For example, in the case of a household air conditioner having a refrigerating capacity of 6.3 kW, the rotation speed N1 corresponding to the heating intermediate condition is 35 rps, and the rotation speed N2 corresponding to the heating rated condition is 85 rps. Therefore, the threshold value used in step S302. Is preferably 60 rps, which is an intermediate value between the rotation speed N1 and the rotation speed N2.

However, the rotation speed of the electric motor 1 may fluctuate. Therefore, in this step S302, it is determined whether or not the state in which the rotation speed of the electric motor 1 is equal to or higher than the threshold value continues for a preset time.

As a result of the comparison in step S302, if the connection state of the coil 3 is delta connection and the rotation speed of the motor 1 is equal to or less than the threshold value, the processes of steps S121 to S124 shown in FIG. 11 are performed. In steps S121 to S124 of FIG. 11, as described in the first embodiment, switching from the delta connection to the Y connection and boosting the bus voltage of the converter 102 are performed.

As a result of the comparison in step S302, when the connection state of the coil 3 is not delta connection (when it is Y connection), or when the rotation speed of the motor 1 is larger than the threshold value (that is, when it is not necessary to switch to Y connection). To step S303.

In step S303, it is determined whether or not it is necessary to switch from the Y connection to the delta connection. That is, it is determined whether or not the connection state of the coil 3 is Y connection and the rotation speed of the motor 1 is larger than the threshold value.

As a result of the comparison in step S303, if the connection state of the coil 3 is Y connection and the rotation speed of the motor 1 is larger than the threshold value, the processes of steps S131 to S134 shown in FIG. 12 are performed. In steps S131 to S134 of FIG. 12, as described in the first embodiment, the Y connection is switched to the delta connection and the bus voltage of the converter 102 is stepped down.

As a result of the comparison in step S303, when the connection state of the coil 3 is not Y connection (when it is delta connection), or when the rotation speed of the motor 1 is larger than the threshold value (that is, when it is not necessary to switch to delta connection). Return to step S105. The processing (steps S109 to S111) when the operation stop signal is received is the same as that of the first embodiment. Other operations and configurations in the fifth modification are the same as in the first embodiment.

As described above, in the fifth modification, high motor efficiency and high motor torque can be obtained by switching the connection state of the coil 3 and the bus voltage of the converter 102 based on the rotation speed of the motor 1.

In the first modification, the second modification, and the third modification, the connection state of the coil 3 and the bus voltage of the converter 102 may be switched based on the rotation speed of the electric motor 1.

Although the rotary compressor 8 has been described here as an example of the compressor, the electric motor of each embodiment may be applied to a compressor other than the rotary compressor 8.

Embodiment 2.
Next, Embodiment 2 of the present invention will be described.

<Composition of air conditioner>
FIG. 37 is a block diagram showing the configuration of the air conditioner 500 of the second embodiment. FIG. 38 is a block diagram showing a control system of the air conditioner 500 of the second embodiment. FIG. 39 is a block diagram showing a control system of the drive device 100a according to the second embodiment. The air conditioner 500 of the second embodiment further includes a compressor temperature sensor 71 as a compressor state detection unit. Compressor temperature sensor 71 is a temperature sensor for detecting a compressor temperature T _C indicating the state of the rotary compressor 8. However, the compressor state detector may be a detector capable of detecting the state of the rotary compressor 8, and is not limited to the temperature sensor.

Except for the compressor temperature sensor 71, the configurations of the air conditioner 500 and the drive device 100a of the second embodiment are the same as those of the air conditioner 5 and the drive device 100 of the first embodiment, respectively.

In the example shown in FIG. 39, the drive device 100a includes a converter 102 that rectifies the output of the power supply 101, an inverter 103 that outputs an AC voltage to the coil 3 of the electric motor 1, and a connection switching unit 60 that switches the connection state of the coil 3. The controller 50 and the compressor temperature sensor 71 are provided. Power is supplied to the converter 102 from a power source 101, which is an alternating current (AC) power source.

Except for the compressor temperature sensor 71, the configuration of the drive device 100a of the second embodiment is the same as that of the drive device 100 of the first embodiment. However, the compressor temperature sensor 71 does not have to be a component of the drive device 100a. The drive device 100a is used together with the rotary compressor 8 to drive the electric motor 1.

The coercive force of a neodymium rare earth magnet containing Nd-Fe-B (neodymium-iron-boron) as a main component, which is used in a permanent magnet type electric motor, has a property of decreasing with temperature. When an electric motor using a neodymium rare earth magnet is used in a high temperature atmosphere of 140 ° C. such as a compressor, the coercive force of the magnet deteriorates with temperature (-0.5 to -0.6% / ΔK). It is necessary to add a (dysprosium) element to improve the coercive force.

When the Dy element is added to the magnet, the coercive force characteristic is improved, but there is a demerit that the residual magnetic flux density characteristic is lowered. When the residual magnetic flux density decreases, the magnet torque of the electric motor decreases and the energizing current increases, so that the copper loss increases. Therefore, there is a great demand for reducing the amount of Dy added in terms of efficiency.

For example, if the maximum temperature of the compressor is lowered while the compressor is being driven, the maximum temperature of the magnet can be reduced and the demagnetization of the magnet can be alleviated. Therefore, it is effective to control the compressor (for example, the rotation speed of the electric motor) based on the compressor temperature threshold value as a threshold value for limiting the temperature of the compressor.

However, if the compressor temperature threshold value is set low, a command to lower the rotation speed of the motor or a command to stop the motor may be issued under a low load (air conditioning load) depending on the set value. In this case, the maximum operating range of the electric motor is narrowed, and the operation of the electric motor is restricted regardless of the situation in the room where the air conditioner is provided (for example, the above temperature difference ΔT).

Therefore, in the second embodiment, the control device 50 issues a command to change the driving method of the electric motor 1 based on a threshold value (compressor temperature threshold value) different depending on the connection state of the coil 3. More specifically, the control unit 50, is detected by the compressor temperature sensor 71 the compressor temperature T _C is, if it is determined to be greater than the compressor temperature threshold value, issues a command to change the driving method of the motor 1 .. As a result, the temperature of the rotary compressor 8 is lowered to protect the rotary compressor 8.

Compressor temperature sensor 71 detects the compressor temperature T _C indicating the state of the rotary compressor 8. In the present embodiment, the compressor temperature sensor 71 is fixed to the discharge pipe 85 of the rotary compressor 8. However, the position where the compressor temperature sensor 71 is fixed is not limited to the discharge pipe 85.

Compressor temperature T _C passes through, for example, the shell 80 of the rotary compressor 8, the discharge pipe 85 of the rotary compressor 8 (e.g., the top of the discharge pipe 85), the refrigerant in the rotary compressor 8 (e.g., a discharge pipe 85 The temperature of at least one of the refrigerant) and the electric motor 1 provided inside the rotary compressor 8. Compressor temperature T _C can be at a temperature other than these elements elements.

Compressor temperature T _C is, for example, the highest temperature measured in the predetermined time. For each measured compressor temperature T _C, it may have been the correlation between temperature data of the rotary in the compressor 8, which is measured in advance and the compressor temperature T _C, is stored in the memory 58 in the controller 50 .. The temperature data in the rotary compressor 8 measured in advance is data indicating the temperature (maximum temperature) in the rotary compressor 8 that fluctuates depending on the circulation amount of the refrigerant, the heat generation temperature of the electric motor 1, and the like. In this case, the compressor temperature T _C detected by the compressor temperature sensor 71 may be used as the first detection value or the second detection value described below, based on the correlation between the compressor temperature T _C The calculated temperature data may be used as a first detection value or a second detection value described later.

Connection state of the coil 3 is first connected state (e.g., Y-connected) when the control device 50 includes a first detection value detected by the compressor temperature sensor 71, the threshold T _Y as the compressor temperature threshold The electric motor 1 is controlled based on (first threshold value). The threshold _TY is, for example, 90 ° C. When a detector other than the temperature sensor is used as the compressor state detection unit, a value other than the temperature may be set as a threshold value.

Specifically, when the first detection value is greater than the threshold value T _Y, the control device 50, at least one temperature detected by the compressor temperature sensor 71 (compressor temperature T _C) motor so as to reduce the 1 is controlled. For example, the control device 50 issues a command to change the rotation speed of the electric motor 1 so that the rotation speed of the electric motor 1 decreases, or stops the drive (rotation) of the electric motor 1. Thus, it is possible to lower the compressor temperature T _C.

When the connection state of the coil 3 is the second connection state (for example, delta connection), the control device 50 sets the second detection value detected by the compressor temperature sensor 71 and the threshold value T _Δ as the compressor temperature threshold value. The electric motor 1 is controlled based on (the second threshold value).

Specifically, when the second detection value is greater than the threshold value T _delta, the control device 50, at least one temperature detected by the compressor temperature sensor 71 (compressor temperature T _C) motor so as to reduce the 1 is controlled. For example, the control device 50 issues a command to change the rotation speed of the electric motor 1 so that the rotation speed of the electric motor 1 decreases, or stops the drive (rotation) of the electric motor 1. Thus, it is possible to lower the compressor temperature T _C.

The electric motor 1 is designed so as not to be demagnetized at the maximum temperature (compressor temperature threshold) that the magnet can reach in consideration of the temperature change due to the heat generation of the electric motor 1, the cooling effect by the refrigerant, and the like. For example, in the present embodiment, the permanent magnet 25 of the electric motor 1 is designed so as not to be demagnetized near the maximum magnet temperature of 140 ° C. In this case, the threshold T _Δ is set to 140 ° C.

Among the connection states of the coil 3 that can be switched by the connection switching unit 60, the lower the line voltage, the higher the compressor temperature threshold value is set. In the present embodiment, the line voltage of the inverter 103 in the delta connection is lower than the line voltage of the inverter 103 in the Y connection. Accordingly, the threshold T _delta, is set to be larger than the threshold value T _Y. As a result, the maximum operating range of the motor 1 (particularly, the maximum rotation speed of the motor 1 in the delta connection) can be prevented from being narrowed.

<Operation of air conditioner>
Next, the basic operation of the air conditioner 500 of the second embodiment (control method of the electric motor 1, the rotary compressor 8 and the air conditioner 500) will be described.
FIG. 40 is a flowchart showing the basic operation of the air conditioner 500 of the second embodiment.

Steps S101 to S105 are the same as those in the first embodiment (FIG. 10). If the operation stop signal has not been received in step S105, the process proceeds to step S401.

The connection switching unit 60 changes the connection state of the coil 3 to delta connection (second connection state in the present embodiment) and Y connection (this implementation) according to the above temperature difference ΔT or the rotation speed of the motor 1. In the form of, it is possible to switch between the first connection state).

The compressor temperature sensor 71 detects the state of the rotary compressor 8 (step S401). In this embodiment, to detect the compressor temperature T _C indicating the state of the rotary compressor 8 _(e.g., the temperature of the discharge pipe 85).

At step S401, connection state of the coil 3 when the Y-connection, for detecting a compressor temperature T _C as a first detected value. Meanwhile, connection states of coil 3 when the delta connection, for detecting a compressor temperature T _C as a second detection value.

Further, the control unit 50, wire connection of the coils 3 is a Y-connection, besides, the compressor temperature T _C is greater determines whether than the threshold value T _Y (step S402).

Result of comparison in step S402, connection state of the coil 3 in Y-connection, and, if the compressor temperature _{T C} is greater than the threshold value _{T Y,} the process proceeds to step S404.

Result of the comparison in step S402, when connection state of the coil 3 (the case of delta connection) if not Y connection, or the compressor temperature T _C is equal to or smaller than the threshold T _Y, the process proceeds to step S403.

In step S403, the control unit 50, wire connection of the coils 3 is a delta connection, besides, the compressor temperature T _C is determined greater or not than the threshold value T _delta.

Result of comparison in step S403, connection state of the coil 3 in delta connection, and, if the compressor temperature _{T C} is greater than the threshold value T _delta, the process proceeds to step S404.

Results of the comparison in the step S403, connection state of the coil 3 (the case of Y connection) if not delta connection, or if the compressor temperature T _C is equal to or smaller than the threshold T _delta, the process returns to step S105.

In step S404, the control device 50 reduces the rotation speed of the electric motor 1. However, the electric motor 1 may be stopped instead of lowering the rotation speed of the electric motor 1. When the electric motor 1 is stopped in step S404, the electric motor 1 is stopped without changing the connection state of the coil 3. When the electric motor 1 is stopped in step S404, for example, the electric motor 1 is started after a predetermined time has elapsed, and then the process returns to step S105.

That is, in step S401 to S404, when connection state of the coil 3 is Y-connection, and controls the motor 1 based on the first detection value and the first threshold value (threshold value _{T Y),} the connection state of the coil 3 In the case of delta connection, the motor 1 is controlled based on the second detected value and the second threshold value (threshold value T _Δ ). This allows the compressor temperature T _C controls the rotary compressor 8 to be lower than the threshold value T _Y or threshold T _delta.

When the operation stop signal is received in step S105, the control device 50 stops the rotation of the electric motor 1 (step S109). If the operation stop signal is received while the motor 1 is stopped in step S404, the process proceeds to step S110 with the motor 1 stopped. Although omitted in FIG. 40, if an operation stop signal is received between steps S401 to S404, the process proceeds to step S109 to stop the rotation of the electric motor 1.

After that, the control device 50 stops the air conditioner 500 (step S110). Specifically, each fan motor of the indoor blower fan 47 and the outdoor blower fan 46 is stopped. After that, the CPU 57 of the control device 50 is stopped, and the operation of the air conditioner 500 is completed.

When the air conditioner 500 is stopped in step S110, it is desirable that the connection state of the coil 3 is delta connection. For example, in step S110, when the connection state of the coil 3 is Y connection, the control device 50 outputs a connection switching signal to the connection switching unit 60, and switches the connection state of the coil 3 from Y connection to delta connection.

<Effect of Embodiment 2>
According to the second embodiment, the electric motor 1 is controlled by using the compressor temperature threshold value in consideration of the connection state of the coil 3. For example, when the detected value detected by the compressor temperature sensor 71 is greater than the compressor temperature threshold value, the motor 1 is controlled so that the compressor temperature T _{C (i.e.,} temperature in the rotary compressor 8) is reduced .. As a result, demagnetization of the electric motor 1 can be prevented, and the electric motor 1 can be appropriately controlled according to the state of the rotary compressor 8.

As described in the first embodiment, in the drive device that operates by switching the connection state of the coil 3 between the Y connection and the delta connection, the delta connection is operated at a high rotation speed as before, and the Y connection is air-conditioned. Operate at a low rotation speed with a small load. Therefore, by switching the connection state of the coil 3 from delta connection to Y-connection, the maximum temperature of the rotary compressor 8 when performing the normal load operation (the maximum value of the compressor temperature T _C), during operation in the delta connection It can be configured so that the maximum temperature of the rotary compressor 8 during operation in the Y connection is lower than that of the rotary compressor 8.

For example, without considering the connection state of the coil 3, a predetermined one compressor temperature threshold value (e.g., the same value as the threshold value T _Y) case of controlling the motor 1 based on a maximum operating range of the motor 1 ( In particular, the maximum number of revolutions of the motor 1 in the delta connection) may be narrowed. Therefore, in the second embodiment, the electric motor 1 is controlled by using a plurality of compressor temperature threshold values in consideration of the connection state of the coil 3.

Specifically, the electric motor 1 is controlled based on a compressor temperature threshold value (for example, threshold value _TY and threshold value T _Δ ) that differs depending on the connection state of the coil 3. Therefore, even if the compressor temperature threshold value is set lower during operation with Y connection than during operation with delta connection, the maximum operating range of motor 1 (particularly, maximum rotation speed of motor 1 with delta connection) is narrow. You can prevent it from getting stuck.

For example, in the configuration for switching the connection state of the coil 3 described in the first embodiment, when the connection state of the coil 3 is Y connection and the motor 1 has a low rotation speed (heating intermediate condition), the lines are connected. The voltage (motor voltage) is configured to be almost equal to the maximum output voltage of the inverter to improve efficiency. In this case, in order to reduce the number of connection switchings, it may be desired to rotate the motor 1 to the highest possible rotation speed. Therefore, the operation is performed with a weakened field, but the weakening current increases and the demagnetization deteriorates.

The lower the temperature, the higher the coercive force of the permanent magnet 25, and it is possible to make it difficult to demagnetize even if the current is increased. Therefore, according to the second embodiment, the compressor temperature threshold value T _Y when connection state of the coil 3 is Y-connection is set lower than the compressor temperature threshold value T _delta when the delta connection. As a result, the maximum temperature of the rotary compressor 8 during operation with Y connection can be set to be lower than that during operation with delta connection. Therefore, it is possible to configure the structure so that it does not demagnetize even if the weakening current increases, it is possible to drive with Y connection up to higher speed rotation, and there is an advantage that the degree of freedom of connection switching is increased. In other words, the motor 1 can be driven in a state where the coercive force of the magnet of the motor 1 is high, and demagnetization can be made difficult even if a larger current is passed through the motor 1. Further, when the connection state of the coil 3 is Y connection, the electric motor 1 can be driven to higher speed rotation with a field weakening.

In addition, when the Y connection of the coil, which has a number of turns close to the number of turns (turns) of the conventional coil without switching the connection, is switched to the delta connection, the field weakening at high speed rotation can be suppressed. It is possible to obtain a configuration that is more resistant to demagnetization in the delta connection.

Further, in the Y connection, the compressor temperature threshold value can be set lower than in the conventional case, so that the demagnetization characteristics can be improved in both the Y connection and the delta connection, and dysprosium (Dy) is added. It is possible to use a magnet that is not used.

For example, as the permanent magnet 25, a rare earth magnet containing neodymium (Nd), iron (Fe) and boron (B) as main components can be used, and the permanent magnet 25 is used as an additive for improving the coercive force. Does not contain dysprosium (Dy). In this case, the residual magnetic flux density of the permanent magnet 25 is 1.36 T to 1.42 T, the coercive force is 1671 kA / m to 1989 kA / m, and the maximum energy product is 354 kJ / m ³ to 398 kJ / m ³ Is.

A modified example of the second embodiment.
Next, a modified example of the second embodiment of the present invention will be described. The above-described second embodiment can be combined with the first embodiment (including each modification). Therefore, in the modified example of the second embodiment, another example of the operation of the air conditioner (control method of the electric motor 1, the rotary compressor 8 and the air conditioner 500) described in the second embodiment will be described. The configuration of the air conditioner of the modified example of the second embodiment is the same as the configuration of the air conditioner 500 of the second embodiment. Therefore, the air conditioner of the modified example of the second embodiment is referred to as an air conditioner 500.

FIG. 41 is a flowchart showing the basic operation of the air conditioner 500 of the modified example of the second embodiment.

Steps S101 to S106 are the same as those in the first embodiment (FIG. 10).

In step S107, the control device 50 switches the coil 3 from the delta connection to the Y connection based on the temperature difference ΔT between the room temperature Ta detected by the room temperature sensor 54 and the set temperature Ts set by the remote controller 55. Judge the necessity. That is, it is determined whether or not the connection state of the coil 3 is delta connection and the absolute value of the temperature difference ΔT is equal to or less than the threshold value ΔTr (step S107).

As a result of comparison in step S107, if the connection state of the coil 3 is delta connection and the absolute value of the temperature difference ΔT is equal to or less than the threshold value ΔTr, the process proceeds to step S121 (FIG. 11).

As a result of the comparison in step S107, when the connection state of the coil 3 is not delta connection (Y connection), or when the absolute value of the temperature difference ΔT is larger than the threshold value ΔTr (that is, it is not necessary to switch to Y connection). In the case), the process proceeds to step S108.

In step S108, it is determined whether or not the coil 3 needs to be switched from the Y connection to the delta connection. For example, as in the first embodiment (step S108), in the control device 50, whether or not the connection state of the coil 3 is Y connection and the absolute value of the temperature difference ΔT is larger than the threshold value ΔTr. To judge.

As a result of comparison in step S108, if the connection state of the coil 3 is Y connection and the absolute value of the temperature difference ΔT is larger than the threshold value ΔTr, the process proceeds to step S131 (FIG. 12). In the modified example of the second embodiment, the processing in steps S131 to S134 shown in FIG. 12 is the processing shown in FIG. 13 (A) (steps S135, S136 and S131 to S134), or shown in FIG. 13 (B). It may be replaced with the processing (steps S137, S138 and S131 to S134).

The processing in steps S106 to S108 shown in FIG. 41 may be replaced with the processing in each modification of the first embodiment (for example, steps S201 to S204 shown in FIG. 35 or steps S301 to S303 shown in FIG. 36). Good.

As a result of the comparison in step S108, when the connection state of the coil 3 is not Y connection (delta connection), or when the absolute value of the temperature difference ΔT is equal to or less than the threshold value ΔTr (that is, it is necessary to switch to delta connection). If not), the process proceeds to step S401.

Steps S401 to S404 are the same as those in the second embodiment (FIG. 40).

When the operation stop signal is received in step S105, the control device 50 stops the rotation of the electric motor 1 (step S109). If the operation stop signal is received while the motor 1 is stopped in step S404, the process proceeds to step S110 with the motor 1 stopped. Although omitted in FIG. 41, even in steps S105 to S108 or steps S401 to S404, when the operation stop signal is received, the process proceeds to step S109 to stop the rotation of the electric motor 1.

After that, the control device 50 (specifically, the connection switching unit 60) switches the connection state of the coil 3 from the Y connection to the delta connection (step S110). If the connection state of the coil 3 is already a delta connection, the connection state is maintained.

Step S111 is the same as that of the first embodiment (FIG. 10).

According to the modified example of the second embodiment, it has the same effect as the effect described in the first embodiment (including each modified example) and the second embodiment.

The features of each of the embodiments and the modifications described above can be appropriately combined with each other.

Although the preferred embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various improvements or modifications are made without departing from the gist of the present invention. be able to.

1 Electric motor, 3,3U, 3V, 3W coil, 5,500 air harmonizer, 5A indoor unit, 5B outdoor unit, 8 rotary compressor (compressor), 9 compression mechanism, 10 stator, 11 stator core, 12 sensors, 20 Rotor, 21 Rotor core, 25 Permanent magnet, 41 Compressor, 42 Four-way valve, 43 Outdoor heat exchanger, 44 Expansion valve, 45 Indoor heat exchanger, 46 Outdoor blower fan, 47 Indoor blower fan, 50 Controller, 50a Indoor Control device, 50b outdoor control device, 50c communication cable, 51 input circuit, 52 arithmetic circuit, 53 output circuit, 54 indoor temperature sensor, 55 remote control, 56 signal receiver, 57 CPU, 58 memory, 60 connection switching section, 61, 62, 63 switches, 71 compressor temperature sensor, 80 shell, 81 glass terminal, 85 discharge tube, 90 shaft, 100, 100a drive, 101 power supply, 102 converter, 103 inverter.

Claims (16)

A drive device used in an air conditioner to drive an electric motor having a coil.
With a converter that generates a bus voltage,
An inverter that converts the bus voltage into an AC voltage and supplies it to the coil.
It is equipped with a connection switching unit that switches the connection state of the coil.
The coil connection state includes a first connection state and a second connection state.
The inverter outputs a line voltage lower in the second connection state than in the first connection state.
Under the heating intermediate condition, the connection state of the coil is the first connection state, and the bus voltage generated by the converter is the first bus voltage V1.
Under the heating rated condition, the connection state of the coil is the second connection state, and the bus voltage generated by the converter is the second bus voltage V2 higher than the first bus voltage V1.
Drive device. When the connection switching unit switches the connection state of the coil from the first connection state to the second connection state, the rotation of the electric motor is temporarily stopped, and the connection switching is performed in the state where the rotation is stopped. The drive device according to claim 1 , wherein the unit switches the connection state of the coil to the second connection state. The coil is a three-phase coil.
The first connection state is a state in which the three-phase coil is connected by Y connection.
The driving device according to claim 1 or 2 , wherein the second connection state is a state in which the three-phase coil is connected by delta connection. The first rotation speed N1 and the second rotation speed N2 of the electric motor satisfy N2 / N1> √3.
When the rotation speed of the electric motor is the first rotation speed N1, the connection switching unit sets the connection state of the coil to the first connection state.
The driving device according to claim 3 , wherein when the rotation speed of the electric motor is the second rotation speed N2, the connection switching unit sets the connection state of the coil to the second connection state. The first bus voltage V1, the second bus voltage V2, the first rotation speed N1 and the second rotation speed N2 are
V2 ≧ (V1 / √3) × N2 / N1
4. The drive device according to claim 4 . The coil is a three-phase coil connected by Y connection or delta connection.
The first connection state is a state in which the three-phase coil has a first number of coil portions connected in series for each phase.
The second connection state is a state in which the three-phase coil has the first number of coil portions connected in parallel for each phase.
The drive device according to claim 1 or 2 . The first number is represented by "n" and
The first rotation speed N1 and the second rotation speed N2 of the electric motor satisfy N2 / N1> n.
When the rotation speed of the electric motor is the first rotation speed N1, the connection switching unit sets the connection state of the coil to the first connection state.
The driving device according to claim 6 , wherein when the rotation speed of the electric motor is the second rotation speed N2, the connection switching unit sets the connection state of the coil to the second connection state. The first bus voltage V1 and the second bus voltage V2, and the first rotation speed N1 and the second rotation speed N2 are
V2 ≧ (V1 / n) × N2 / N1
7. The drive device according to claim 7 . The first rotation speed N1 corresponds to the heating intermediate condition, and corresponds to the heating intermediate condition.
The drive device according to any one of claims 4, 5, 7, and 8 , wherein the second rotation speed N2 corresponds to the heating rated condition. The first rotation speed N1 corresponds to the operating condition having the highest ratio in the annual energy consumption efficiency (APF) of the air conditioner.
The second rotation speed N2 corresponds to any one of claims 4, 5, 7, 8 and 9 , which corresponds to the operating condition in which the ratio of the air conditioner to the annual energy consumption efficiency is the second highest. Drive device. Further equipped with a power supply for supplying an AC power supply voltage to the converter,
The drive device according to any one of claims 1 to 10 , wherein the first bus voltage V1 is the same as √2 times the effective value of the power supply voltage. The connection switching portion is
When the rotation speed of the electric motor is equal to or less than the threshold value, the connection state of the electric motor is switched to the first connection state.
The drive device according to any one of claims 1 to 11 , wherein when the rotation speed of the electric motor is larger than the threshold value, the connection state of the electric motor is switched to the second connection state. The drive device according to any one of claims 1 to 12 , wherein the inverter performs field weakening control according to the rotation speed of the electric motor. The driving device according to any one of claims 1 to 13 , wherein the converter has a SiC element or a GaN element. An electric motor with a coil and
The compressor driven by the electric motor and
An air conditioner comprising the driving device according to any one of claims 1 to 14 for driving the electric motor. A drive method for driving an electric motor having a coil by using a converter that generates a bus voltage and an inverter that converts the bus voltage into an AC voltage and supplies the coil to the coil.
The coil connection state includes a first connection state and a second connection state, and the inverter outputs a line voltage lower in the second connection state than in the first connection state. And
Under the heating intermediate condition, the connection state of the coil is set to the first connection state, the bus voltage generated by the converter is set to the first bus voltage V1, and under the heating rated condition, the connection state of the coil is set to the first connection state. 2. A method of driving an electric motor, which comprises a connection state of 2 and a step of switching the bus voltage generated by the converter to a second bus voltage V2 higher than the first bus voltage V1.

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