WO2021084617A1 - Electric motor drive device, refrigeration cycle device, air conditioner, water heater, and refrigerator - Google Patents

Abstract

This electric motor drive device (2) has: a connection switching device (60) having switches (61-63) and switching the connection states of the windings (71-73) of an electric motor (7) by performing switching operation of the switches during the rotating operation of the electric motor; an inverter (30) which applies AC voltages to the windings via the switches and to which reverse electromotive forces are applied from the windings of the electric motor during the rotating operation via the switches; and a control device (100) for controlling the rotating operation of the electric motor by controlling the inverter and causing the connection switching device to switch the connection states. The electric motor drive device is equipped with: a first step having a current control period (Pc) in which the first effective values of the AC current flowing through the windings are made closer to zero than the second effective values of the AC currents flowing through the windings before the switching operation of the switches; and a second step being the step after the first step and having a power supply stop period (Ps) in which the AC voltages output by the inverter are stopped. The switching operation of the switches is performed during the period of the second step.

Description

Electric motor drive, refrigeration cycle device, air conditioner, water heater, and refrigerator

The present invention relates to an electric motor drive device, a refrigeration cycle device including the electric motor drive device, and an air conditioner, a water heater, and a refrigerator equipped with the refrigeration cycle device.

Conventionally, a drive wheel, a motor connected so as to transmit a driving force to the drive wheel and having a switchable winding, an input unit for instructing the output of the motor, and a control signal based on an instruction from the input unit. The output control unit, the inverter whose duty ratio is adjusted based on the control signal from the control unit to supply the output voltage to the motor, the winding switching unit that switches the winding, and the motor current that flows through the winding are detected. There is a saddle-type vehicle including a current detection unit and a phase detection unit that detects the phase of the motor. The control unit of this saddle-type vehicle has a switching determination unit that determines whether or not the winding switching condition is satisfied, and a duty ratio adjustment period when the winding switching condition is satisfied, and an instruction from the input unit. The adjustment unit adjusts the duty ratio of the inverter based on the motor current detected by the current detection unit and the phase of the motor detected by the phase detection unit so that the motor current becomes 0 regardless of the above. It includes a switching instruction unit that instructs the winding switching unit to switch the winding during the duty ratio adjustment period (see, for example, Patent Document 1).

JP 2013-62888 (for example, claim 1, FIGS. 2 to 6)

In the technique described in Patent Document 1 (for example, FIG. 2), when the motor current is controlled to 0, it is necessary to match the counter electromotive voltage of the motor with the output voltage of the inverter. That is, when the winding is switched, the power supply by the inverter is continued. When a mechanical relay is used in the switch (42a to 42c) for switching the winding, the terminal (TU3) is turned off from the conduction state between the terminals (TU2 and TU3) of the switch (42a), and the terminal (TU3) is turned off. When the TU5) is turned on, that is, when the terminals (TU2 and TU5) are operated to be in a conductive state, it is practically impossible to completely control the motor current to 0, and the motor current is pulled from the terminal (TU3). An arc discharge occurs when the terminal (TU5) is peeled off, and a potential difference is generated between the terminals (TU2 and TU5) because the inverter is energized. Therefore, an arc discharge due to the potential difference occurs immediately before the terminals (TU5) come into contact with each other. .. When such two arc discharges occur at the same time, a moment occurs in which the terminal (TU2) becomes conductive on both the terminals (TU3 and TU5). In that case, a closed loop is generated via the winding (RU) and the terminals (TU3, TU5), a short circuit state occurs due to the induced voltage of the winding (RU), and the mechanical relay may be welded and failed. ..

The present invention has been made in view of the above, and the switching operation of the switch for switching the connection state of the windings of the electric motor can be performed without stopping the rotational operation of the electric motor, and the connection state can be switched. An object of the present invention is to provide an electric motor drive device which is less likely to cause a failure due to the failure and a device provided with the electric motor drive device.

The electric motor drive device according to the present invention includes a connection switching device that has a switching device and switches the connection state of the windings of the electric motor by performing the switching operation of the switching device during the rotation operation of the electric motor, and the switching device. An AC voltage is applied to the winding through the winding, and a countercurrent voltage is applied from the winding of the electric motor in rotation operation via the switch, and the electric motor is controlled by controlling the inverter. It has a control device that controls the rotation operation and causes the connection switching device to switch the connection state, and the first effective value of the alternating current flowing through the winding is before the switching operation of the switching device. The first stage having a current control period closer to zero than the second effective value of the AC current flowing through the winding, and the stage after the first stage, the AC voltage output by the inverter is stopped. A second stage having a power supply stop period is provided, and the switching operation of the switch is executed during the period of the second stage.

According to the present invention, after a current control period in which the effective value of the alternating current flowing in the winding is controlled to approach zero, a period for stopping the energization of the inverter is provided, and the connection switching device is switched within that period. Since the device is switched, the connection switching device is less likely to fail, and the life of the motor drive device can be extended.

Further, according to the present invention, the connection state of the winding is switched during the current control period in which the rotational operation of the electric motor is not stopped. Therefore, it is not necessary to suspend the rotational operation of the motor and then restart the motor in order to switch the connection state of the windings.

It is the schematic which shows the structural example of the air conditioner (including a refrigerating cycle apparatus) of embodiment. It is a schematic diagram which shows the structural example of the water heater (including the refrigerating cycle apparatus) of embodiment. It is the schematic which shows the structural example of the refrigerator (including the refrigerating cycle apparatus) of embodiment. It is a schematic wiring diagram which shows the electric motor drive device of Embodiment 1 of this invention. It is a figure which shows the structure of the inverter of FIG. It is a wiring diagram which shows the winding of the electric motor of FIG. 1 and the connection switching device in detail. It is a wiring diagram which shows the detail of the switching device of the connection switching device of FIG. (A) and (b) are diagrams conceptually showing windings of electric motors in different wiring states. It is a functional block diagram which shows an example of the control apparatus used in Embodiment 1. FIG. It is a figure which shows the voltage command calculation part of FIG. 9 in detail. It is a waveform figure which shows the operation of the electric motor drive device of Embodiment 1. FIG. It is a wiring diagram which shows the winding of the electric motor and the connection switching device in Embodiment 2 of this invention. It is a circuit diagram which shows the configuration example which used the MOS transistor for the switch of the connection switching device of FIG. It is a figure which shows the example of the on and off states of the MOS transistor of the switch of FIG. 13 in a tabular form. It is a wiring diagram which shows the winding of the electric motor and the connection switching device in Embodiment 3 of this invention.

Hereinafter, with reference to the accompanying drawings, an electric motor drive device according to an embodiment of the present invention, a refrigerating cycle device including the refrigerating cycle applicable device, an air conditioner equipped with the refrigerating cycle device, and a hot water supply. The machine and the refrigerator will be described. The embodiments shown below are merely examples, and the electric motor drive device and each device provided with the electric motor drive device can be modified in various ways within the scope of the present invention. In the following description, the components with the same reference numerals have the same or similar functions.

FIG. 1 is a schematic view showing a configuration example of an air conditioner (including a refrigeration cycle device 900) of the embodiment. As shown in FIG. 1, the refrigeration cycle device 900 can perform a heating operation or a cooling operation by the switching operation of the four-way valve 902.

During the heating operation, as shown by the solid line arrow, the refrigerant is pressurized by the compressor 904 and sent out, and the four-way valve 902, the indoor heat exchanger 906, the expansion valve 908, the outdoor heat exchanger 910 and the four-way valve 902. It returns to the compressor 904 through. During cooling operation, as shown by the broken line arrow, the refrigerant is pressurized by the compressor 904 and sent out, and the four-way valve 902, the outdoor heat exchanger 910, the expansion valve 908, the indoor heat exchanger 906 and the four-way valve 902. It returns to the compressor 904 through.

During the heating operation, the heat exchanger 906 acts as a condenser to release heat (heats the room), and the heat exchanger 910 acts as an evaporator to absorb heat. During the cooling operation, the heat exchanger 910 acts as a condenser to release heat, and the heat exchanger 906 acts as an evaporator to absorb heat (cool the room). The expansion valve 908 depressurizes the refrigerant and expands it. The compressor 904 is driven by an electric motor 7 whose speed is variably controlled by the electric motor drive device 2.

FIG. 2 is a schematic view showing a configuration example of the heat pump type water heater (including the refrigeration cycle device 900a) of the embodiment. As shown in FIG. 2, in the refrigeration cycle apparatus 900a, the heat exchanger 906 acts as a condenser to release heat (warms water), and the heat exchanger 910 acts as an evaporator to absorb heat. .. The compressor 904 is driven by an electric motor 7 whose speed is variably controlled by the electric motor drive device 2.

FIG. 3 is a schematic view showing a configuration example of the refrigerator (including the refrigerating cycle device 900b) of the embodiment. As shown in FIG. 3, in the refrigeration cycle apparatus 900b, the heat exchanger 910 acts as a condenser to release heat, and the heat exchanger 906 acts as an evaporator to absorb heat (cooling the inside of the refrigerator). To do). The compressor 904 is driven by an electric motor 7 whose speed is variably controlled by the electric motor drive device 2.

<< 1 >> Embodiment 1.
<< 1-1 >> Outline of the first embodiment FIG. 4 is a schematic wiring diagram showing the electric motor drive device 2 of the first embodiment of the present invention together with the electric motor 7 and the AC power supply 4. The electric motor drive device 2 is for driving the electric motor 7. As shown in FIG. 4, the electric motor driving device 2 includes an inverter 30, a connection switching device 60, and a control device 100. Further, the electric motor drive device 2 includes AC power input terminals 2a and 2b, a reactor 8, a rectifier circuit 10, a capacitor 20, a control power generation circuit 80, a bus current detecting means 85, and an electric amount detecting unit 90. May be provided.

The connection switching device 60 has switches (switch circuits) 61 to 63, and by performing the switching operation of the switching devices 61 to 63 during the rotation operation of the electric motor 7, the connection state of the windings 71 to 73 of the electric motor 7 ( (Connection state) is switched. The inverter 30 applies an AC voltage to the windings 71 to 73 via the switches 61 to 63, and receives a counter electromotive voltage from the windings 71 to 73 of the electric motor 7 rotating via the switches 61 to 63. It is applied.

The control device 100 controls the rotational operation of the electric motor 7 by controlling the inverter 30. Further, the control device 100 causes the connection switching device 60 to switch the connection state of the windings. In the first embodiment, in the control device 100, the value of the alternating current flowing through the windings 71 to 73 (the first effective value) is the value of the alternating current flowing through the windings before the switching operation of the switches 61 to 63. The switching operation of the switches 61 to 63 is executed within the current control period Pc (also referred to as “zero current control period”) which is closer to zero than (second effective value).

In the present application, the connection state of the winding includes both the connection state of the winding (for example, Y connection and Δ connection) and the number of turns of the winding. The switching of the number of turns of the winding will be described in the third embodiment. Further, when the switches 61 to 63 are configured by the mechanical relay, the current control period Pc can be set to several hundred milliseconds or less. When the switches 61 to 63 are composed of semiconductor switches, the current control period Pc can be set to several milliseconds or less. Further, when the electric motor 7 is used as a compressor of a refrigerating cycle device such as an air conditioner, a heat pump type water heater, or a refrigerator, the current control period Pc can be set within a range of several msec to 1 second.

<< 1-2 >> Configuration of the first embodiment The control device 100 includes, for example, a memory as a storage device for storing control information as a software program, and a CPU (Central Processing Unit) as an information processing device for executing this program. It is composed of a microcomputer (microcomputer) equipped with a device, a DSP (Digital Signal Processor), or the like. Further, the control device 100 may be composed of dedicated hardware (for example, a processing circuit). Hereinafter, a case where the control device 100 is composed of a microcomputer will be described.

The AC power input terminals 2a and 2b are connected to the external AC power supply 4. An AC voltage is applied from the AC power supply 4 to the AC power supply input terminals 2a and 2b. The applied voltage has, for example, an amplitude (effective value) of 100 V or 200 V or the like, and a frequency of 50 Hz or 60 Hz or the like.

The rectifier circuit 10 generates a DC voltage by receiving AC power from the AC power supply 4 via the input terminals 2a and 2b and the reactor 8 and rectifying the rectifier. The rectifier circuit 10 is a full-wave rectifier circuit formed by bridging rectifier elements 11 to 14 such as diodes.

The capacitor 20 smoothes the DC voltage generated by the rectifier circuit 10 and outputs the DC voltage V20.

FIG. 5 is a diagram showing the configuration of the inverter 30 of FIG. As shown in FIG. 5, the inverter 30 has an inverter main circuit 310 and a drive circuit 350. The input terminal of the inverter main circuit 310 is connected to the electrode of the capacitor 20. The line connecting the output of the rectifier circuit 10, the electrode of the capacitor 20, and the input terminal of the inverter main circuit 310 is called a DC bus.

The inverter 30 is controlled by the control device 100, and the switching elements 311 to 316 of the six arms of the inverter main circuit 310 operate on and off. By this on / off operation, the inverter 30 generates a three-phase alternating current having a variable frequency and a variable voltage, and supplies the three-phase alternating current to the motor 7. Rectifying elements 321 to 326 for reflux are connected in parallel to the switching elements 311 to 316, respectively.

The motor 7 is a three-phase permanent magnet synchronous motor, and the end of the stator winding (hereinafter also referred to as “winding”) is pulled out to the outside of the motor 7, and star connection (Y connection) and delta connection (Y connection) and delta connection ( It is possible to switch to any of (Δ connection). This switching is performed by the connection switching device 60. When the Y connection is referred to as the first connection, the Δ connection is the second connection, and when the Δ connection is referred to as the first connection, the Y connection is the second connection. Further, the connection state of the winding may be three or more types.

FIG. 6 is a wiring diagram showing the stator winding and the connection switching device 60 of the electric motor 7 in more detail. As shown in FIG. 6, the first ends 71a, 72a, 73a of the three- phase windings 71, 72, 73 of the electric motor 7 composed of the U phase, the V phase, and the W phase are the external terminals 71c, It is connected to 72c and 73c, respectively. The second ends 71b, 72b, 73b of the U-phase, V-phase, and W- phase windings 71, 72, and 73 of the electric motor 7 are connected to the external terminals 71d, 72d, and 73d, respectively. In this way, the electric motor 7 can be connected to the connection switching device 60. Further, the U-phase, V-phase, and W-phase output lines of the inverter 30 are connected to the external terminals 71c, 72c, and 73c.

In the illustrated example, the connection switching device 60 is composed of switching devices 61 to 63. As the switching devices 61, 62, 63, an electromagnetic contactor whose contacts are opened and closed electromagnetically is used. Such magnetic contactors include what are called relays, contactors and the like.

FIG. 7 is a wiring diagram showing a configuration example of the switches 61 to 63. The switches 61 to 63 are configured as shown in FIG. 7, for example, and have different connections depending on whether a current is flowing through the exciting coils 611, 621, 631 and when no current is flowing. Take the state. The exciting coils 611, 621 and 631 are connected via the semiconductor switch 604 so as to receive the switching power supply voltage V60. The opening and closing of the semiconductor switch 604 is controlled by the switching control signal Sc output from the control device 100. If the current supply from the microcomputer included in the control device 100 is sufficiently secured, the operation may be performed so that the current flows directly from the microcomputer to the exciting coil.

The common contact 61c of the switch 61 is connected to the external terminal 71d via the lead wire 61e. The normally closed contact 61b is connected to the neutral point node 64, and the normally open contact 61a is connected to the V-phase output line 332 of the inverter 30.

The common contact 62c of the switch 62 is connected to the external terminal 72d via the lead wire 62e. The normally closed contact 62b is connected to the neutral point node 64, and the normally open contact 62a is connected to the W phase output line 333 of the inverter 30.

The common contact 63c of the switch 63 is connected to the external terminal 73d via the lead wire 63e. The normally closed contact 63b is connected to the neutral point node 64, and the normally open contact 63a is connected to the U-phase output line 331 of the inverter 30.

When no current is flowing through the exciting coils 611, 621, 631, the switches 61, 62, 63 are switched to the normally closed contact side, that is, the common contacts 61c, 62c, as shown in FIG. , 63c are connected to the normally closed contacts 61b, 62b, 63b. In this state, the electric motor 7 is in the Y connection state.

When a current is flowing through the exciting coils 611, 621, 631, the switches 61, 62, 63 are switched to the normally open contact side, that is, the common contacts 61c, 62c, 63c are in the opposite direction of the drawing. It is in a state of being connected to the normally open contacts 61a, 62a, 63a. In this state, the electric motor 7 is in the Δ connection state.

Here, the advantages of using an electric motor 7 that can be switched to either a Y connection or a Δ connection will be described with reference to FIGS. 8 (a) and 8 (b). FIG. 8A conceptually shows the connection state of the winding when the Y connection is made, and FIG. 8B conceptually shows the connection state of the winding when the Δ connection is made.

The line voltage at the time of Y connection is V _Y , the current flowing into the winding is I _Y , the line voltage at the time of Δ connection is V _Δ , the current flowing into the winding is I _Δ, and the voltage applied to the winding of each phase. Assuming that are equal to each other, there is a relationship of the following equations (1) and (2).
V _Δ = V _Y / √3 (1)
I _Δ = √3 × I _Y (2)

_{When the voltage V Y} and current I _Y at the time of Y connection and the voltage V _Δ and current I _Δ at the time of Δ connection have the relationship of the equations (1) and (2), the electric power is connected at the time of Y connection and the time of Δ connection. The power supplied to is equal to each other. That is, when the electric power supplied to the electric motor is equal to each other, the current is larger in the Δ connection and the voltage required for driving is lower.

It is conceivable to select the connection state according to the load conditions, etc. by utilizing the above properties. For example, when the load is low, the Y connection may be used for low-speed operation, and when the load is high, the Δ connection may be used for high-speed operation. By doing so, the efficiency at low load can be improved, and the output at high load can be increased.

Below, this point will be described in more detail in the case of the electric motor that drives the compressor of the air conditioner. As the electric motor 7 for driving the compressor of the air conditioner, a synchronous motor having a permanent magnet in the rotor is widely used in order to meet the demand for energy saving. Further, in recent air conditioners, when the difference between the room temperature and the set temperature is large, the room temperature is quickly brought closer to the set temperature by high-speed operation of rotating the electric motor 7 at a high speed, and when the room temperature is close to the set temperature, the electric motor is used. Room temperature is maintained by low-speed operation in which 7 is rotated at a low speed. When controlled in this way, the ratio of the low-speed operation time to the total operation time is large.

When a synchronous motor is used, the counter electromotive force increases as the rotation speed increases, and the voltage value required for driving increases. This counter electromotive force is higher in the Y connection than in the Δ connection as described above.

In order to suppress the back electromotive force at high speed, it is conceivable to reduce the magnetic force of the permanent magnet or reduce the number of turns of the stator winding. However, if this is done, the current for obtaining the same output torque increases, so that the current flowing through the motor 7 and the inverter 30 increases, and the efficiency decreases.

Therefore, it is conceivable to switch the connection state according to the number of rotations. For example, when high-speed operation is required, the Δ connection state is set. By doing so, the voltage required for driving can be reduced to 1 / √3 (compared to the Y connection). Therefore, it is not necessary to reduce the number of turns of the winding, and it is not necessary to use the weakening magnetic flux control.

On the other hand, in low-speed rotation, the current value can be reduced to 1 / √3 compared to the Δ connection by setting the Y connection state. Further, the winding can be designed to be suitable for driving at a low speed in the Y connection state, and the current value can be reduced as compared with the case where the Y connection is used over the entire speed range. .. As a result, the loss of the inverter 30 can be reduced and the efficiency can be improved.

As described above, it is significant to switch the connection state according to the load condition, and the connection switching device 60 is provided in order to enable such switching.

The bus current detecting means 85 shown in FIG. 4 detects the bus current, that is, the DC current Idc input to the inverter 30. The bus current detecting means 85 includes a shunt resistor inserted in the DC bus and supplies an analog signal indicating the detection result to the control device 100. This signal (detection signal) is converted into a digital signal by an A / D (Analog to Digital) converter (not shown) in the control device 100 and used for processing inside the control device 100.

As described above, the control device 100 controls the switching of the connection state by the connection switching device 60 and also controls the operation of the inverter 30. To control the inverter 30, the control device 100 generates PWM (Pulse Width Modulation) signals Sm1 to Sm6 and supplies them to the inverter 30.

As shown in FIG. 5, the inverter 30 includes a drive circuit 350 in addition to the inverter main circuit 310, and the drive circuit 350 generates drive signals Sr1 to Sr6 based on the PWM signal. The drive circuit 350 controls the switching elements 311 to 316 to be turned on and off by the drive signals Sr1 to Sr6, whereby a three-phase AC voltage having a variable frequency and a variable voltage is applied to the motor 7.

While the PWM signals Sm1 to Sm6 are of the signal level magnitude (0 to 5V) of the logic circuit, the drive signals Sr1 to Sr6 are voltage levels required to control the switching elements 311 to 316, for example. , A signal having a magnitude from + 15V to -15V. Further, the PWM signals Sm1 to Sm6 use the ground potential of the control device 100 as a reference potential, whereas the drive signals Sr1 to Sr6 are the potentials of the negative terminals (emitter terminals) of the corresponding switching elements. Is the reference potential.

FIG. 9 is a functional block diagram showing an example of the control device 100 of FIG. As shown in FIG. 9, the control device 100 includes an operation control unit 102 and an inverter control unit 110.

The operation control unit 102 outputs an instruction signal based on the command signal Qe provided by the electric energy detection unit 90. The electric amount detection unit 90 transmits a command signal based on the electric amount of an electric signal indicating the room temperature (temperature of the air-conditioned space) detected by a temperature sensor (not shown), and instruction information from an operation unit (for example, a remote control) (not shown). It receives the indicated command signal and controls the operation of each part of the air conditioner. The instructions from the operation unit include information indicating the set temperature, selection of the operation mode, instructions for starting and ending the operation, and the like.

The operation control unit 102 determines, for example, whether the stator winding of the motor 7 is Y-connected or Δ-connected, and determines the target rotation speed, and based on the determination, the switching control signal Sc and the frequency command value ω ^* Output. For example, when the difference between the room temperature and the set temperature is large, it is decided to make a Δ connection, the target rotation speed is set to a relatively high value, and after startup, the frequency is gradually increased to the frequency corresponding to the above target rotation speed. Outputs the rising frequency command value ω ^*.

When the frequency corresponding to the target rotation speed is reached, the state is maintained until the room temperature approaches the set temperature, and when the room temperature approaches the set temperature, the motor is stopped once, switched to the Y connection, and the target rotation is relatively low. Outputs the ^{frequency command value ω *} that gradually rises to the frequency corresponding to the number. When the frequency corresponding to the target rotation speed is reached, control is performed to maintain the room temperature close to the set temperature. This control includes frequency adjustment, motor stop, restart, and the like.

As shown in FIG. 9, the inverter control unit 110 includes a current restoration unit 111, a three-phase two-phase conversion unit 112, a frequency compensation unit 113, a primary frequency calculation unit 114, a voltage command calculation unit 115, and a two-phase three-phase conversion unit. It has 116, a PWM generation unit 117, an electric angle phase calculation unit 118, and an exciting current command control unit 119.

_{The current restoration unit 111 restores the phase currents i u} , _iv , i _w flowing through the motor 7 based on the value of the direct current Idc detected by the bus current detecting means 85 (FIG. 4). The current restoring unit 111 samples the DC current Idc detected by the bus current detecting means 85 at a timing determined based on the PWM signal provided by the PWM generating unit 117, thereby causing the phase currents i _u , _iv , and so on. Restore i _w.

The three-phase two-phase conversion unit 112 uses the electric angle phase θ generated by the electric angle phase calculation unit 118, which will be described later, for the current values of _{the phase currents i u} , _iv , and i _{w restored by the current restoration unit 111.} The exciting current component (also referred to as “γ-axis current”) i _γ and the torque current component (also referred to as “δ-axis current”) i _δ are converted into current values on the γ-δ axis.

_{The exciting current command control unit 119 obtains the optimum exciting current command value i γ} ^* that is most efficient for driving the electric motor 7 based on the torque current component (δ-axis current) i _δ. In FIG. 9, but based on the torque current component i _[delta] seeking the exciting current command value i _gamma ^*, exciting current component i _gamma, exciting current command value i _gamma based on the frequency command value omega ^* The same effect can be obtained by obtaining ^*.

In the exciting current command control unit 119, the output current is equal to or higher than a predetermined value (or maximum) based on _{the torque current component i δ} (or the exciting current component i _γ , the frequency command value ω ^{*), that is, the current value is set.} _{The exciting current command value i γ} ^* is output so that the current phase angle βm (not shown) is equal to or less than (or the minimum) a predetermined value.

FIG. 10 is a diagram showing the voltage command calculation unit 115 of FIG. 9 in detail. As shown in FIG. 10, the voltage command calculation unit 115 includes the γ-axis current i _γ and the δ-axis current i _δ obtained from the three-phase two-phase conversion unit 112, the frequency command value ω ^*, and the excitation current command control. Based on the exciting current command value i _γ ^* obtained from unit 119, the voltage command values V _γ ^* and V _δ ^* are output.

The controller 1152 is, for example, a proportional integration (PI) controller, and frequency estimation is performed based on ^{the difference (ω * -ωest) between the frequency command value ω *} and the frequency estimation value ωest generated by the frequency estimation unit 1151. Outputs the δ-axis current command value i _δ ^* such that the value ωest matches the frequency command value ω ^* .

The frequency estimation unit 1151 estimates the frequency of the electric motor 7 based on _{the γ-axis currents i γ} and the δ-axis currents i _δ and the voltage command values V _γ ^* and V _δ ^{*, and generates a frequency estimation value ωest.}

The switching unit 1155 selects the value of the δ-axis current command value i _δ ^** from either the δ-axis current command value i _δ ^* or 0. For example, the controller 1156 such as the PI controller sets the δ-axis current. i _[delta] and outputs a ^* a [delta] -axis voltage value V _[delta] as to coincide with the [delta] -axis current value i _[delta] ^**.

The switching unit 1153 selects the value of the γ-axis current command value i _δ ^** from either the γ-axis current command value i _γ ^* or 0. For example, the controller 1154 such as the PI controller sets the γ-axis current. i _gamma outputs a ^* a gamma-axis voltage command value V _gamma to match the gamma-axis current value i _gamma ^**.

The two-phase three-phase conversion unit 116 shown in FIG. 9 has a γ-axis voltage command value V _γ ^* and a δ-axis voltage command value V _δ ^* (voltage command value in a two-phase coordinate system) obtained by the voltage command calculation unit 115. _{Is converted into the output voltage command value (three-phase voltage command value) V u} ^* , V _v ^* , V _w ^* of the three-phase coordinate system using the electric angle phase θ obtained by the electric angle phase calculation unit 118 and output. To do.

The PWM generation unit 117 generates and outputs PWM signals Sm1 to Sm6 based on the _{three-phase voltage command values V u} ^* , V _v ^* , and V _w ^* obtained from the two-phase three-phase conversion unit 116.

The stop signal St provided by the operation control unit 102 is given to, for example, the PWM generation unit 117, and the PWM generation unit 117 immediately stops the output of the PWM signals Sm1 to Sm6 when the stop signal St is received.

The drive circuit 350 shown in FIG. 5 generates drive signals Sr1 to Sr6 based on the PWM signals Sm1 to Sm6.

_{In the example of FIG. 9, the configuration for restoring the phase currents i u} , _iv , i _w from the DC current Idc on the input side of the inverter 30 is described, but the output lines 331, 332, and 333 of the inverter 30 are used. A current detector may be provided, and the current detector may be used to detect the phase current. In this case, the current detected by the current detector may be used instead of the current restored by the current restoration unit 111.

Further, when a three-phase permanent magnet synchronous motor is used for the motor 7, if an excessive current flows through the motor 7, irreversible demagnetization of the permanent magnet occurs and the magnetic force decreases. When such a state occurs, the current for outputting the same torque increases, which causes a problem that the loss worsens. Therefore, the phase currents _{i u,} i v, and _{i w} or DC current Idc is supplied to the control unit 100, when an excessive current flows to the motor 7, to the motor 7 by stopping the PWM signal Sm1 ~ Sm6 By stopping the energization, it is possible to prevent irreversible demagnetization. Incidentally, by providing the phase currents _{i u, i v, i w} or removing noise to the DC current Idc LPF (Low Pass Filter), can be prevented from stopping accidentally Sm1 ~ Sm6 by noise Yes, it is possible to improve the reliability.

Here, when an electric motor 7 capable of switching to either Y connection or Δ connection is used, the current value at which irreversible demagnetization occurs in the Y connection and Δ connection (I _Y and I _{Δ in FIG. 8).} ) Is approximately √3 times different, and the Δ connection is √3 times higher than the Y connection. Therefore, if the protection level of irreversible demagnetization is set according to the Y connection, the protection of I _Δ will be applied quickly, and it will be difficult to expand the operating range. Therefore, by switching the protection level according to the Y connection and the Δ connection in the control device 100, it is possible to reliably protect the motor 7 from irreversible demagnetization in each winding, and the motor drive device with improved reliability. Can be obtained.

Regarding the protection level, the magnetic force in the initial state of the motor 7 is set to 100%, and the current value (for example, the magnetic force is reduced to 97%) within a range that does not affect the performance when irreversible demagnetization occurs. It can be set to the current value), but there is no problem even if the set current value of the protection level is changed according to the equipment to be used.

<< 1-3 >> Operation of Embodiment 1 Hereinafter, the operation of the electric motor drive device 2 when the switching devices 61 to 63 of the connection switching device 60 are switched during the operation of the electric motor 7 (that is, during the rotational operation). Will be described. First, a problem of the prior art, that is, an operation in the electric motor drive device which does not have the features of the present invention will be briefly described with reference to FIG.

<Operation of the motor drive device in the comparative example>
When the electric motor is operating, that is, when the current is flowing through the switches 61, 62, 63 constituting the connection switching device 60, and the current flowing through the exciting coils 611, 621, 631 is operated, the common contacts 61c, 62c , 63c are connected to the normally closed contacts 61b, 62b, 63b or the normally open contacts 61a, 62a, 63a. Assuming that the power supply from the inverter 30 to the motor 7 continues when the switching occurs and the rotation speed Nm of the motor 7 is not yet zero, an arc discharge occurs between the contacts of the switches 61, 62, and 63. It may occur, which may cause a failure such as contact welding.

In order to avoid such a failure, the power supply from the inverter 30 to the electric motor 7 is stopped before the connection switching device 60 is operated, and the rotation speed Nm of the electric motor 7 is zero (that is, the rotation operation is stopped). By doing so, switching can be performed without generating an arc discharge between the contacts of the switches 61, 62, and 63.

However, when the rotation speed Nm of the electric motor 7 is set to zero, when the load applied to the electric motor 7 when the electric motor 7 is restarted is, for example, the compressor 904 (FIG. 1), the state of the refrigerant is not stable. Therefore, the torque required for restarting increases, the current at startup increases, and in the worst case, restarting may not be possible. Therefore, it is necessary to restart the electric motor 7 after a lapse of time until the state of the refrigerant is sufficiently stabilized without operating the electric motor 7. Therefore, the compressor 904 cannot pressurize the refrigerant, which may cause the room temperature to rise or fall due to a decrease in cooling or heating capacity, and the room temperature may not be kept constant.

<Operation of motor drive device 2>
Therefore, in the electric motor 7 of the first embodiment, the value (effective value) of the current flowing through the winding of the electric motor 7 or the connection switching device 60 during the rotational operation (during operation) of the electric motor 7 is controlled so as to approach zero (current). After the control period Pc), the power supply from the inverter 30 to the motor 7 is stopped (power supply stop period Ps), and in that state (during the power supply stop period Ps), the switch of the connection switching device 60 is operated. Switching is completed without generating an arc discharge or an excessive current between the contacts of the switches 61, 62, 63.

The current control period Pc is a period in which the inverter applies an AC voltage to the motor so as to cancel the counter electromotive voltage generated by the rotational operation of the motor 7. In this way, the value (effective value) of the current flowing through the winding of the electric motor 7 can be brought close to zero without making the rotation speed Nm of the electric motor 7 zero, that is, without stopping the rotation operation. After that, since the power supply of the inverter 30 is stopped during the power supply stop period Ps, the voltage supply from the inverter 30 to the connection switching device 60 is stopped, so that the windings 71 to 73 are connected in a state where the reliability is further improved. Can be switched. Therefore, in the case of an air conditioner, it is not necessary to stop the rotation operation of the electric motor 7 when switching the connection state, so that the waiting time until the refrigerant stabilizes due to the stop of the rotation operation becomes unnecessary, and the room temperature rises or falls. Can be suppressed.

In FIG. 10, the voltage command calculation unit 115 is _{operated by the switching unit 1155 to select 0 for the delta-axis current command value i δ} ^** , so that the delta-axis current i _δ becomes the delta-axis current command value i _δ ^* . Outputs a delta-axis voltage command value V _δ ^* that matches, that is, the delta-axis current command value i _δ ^{** matches 0.} Further, the voltage command calculation unit 115 is _{operated by the switching unit 1153 to select 0 for the γ-axis current command value i γ} ^** , so that the γ-axis current i _γ matches the γ-axis current command value i _γ ^*. That is, the γ-axis voltage command value V _γ ^* is output so that the γ-axis current command value i _γ ^{** matches 0.} After that, by stopping the output of the PWM signals Sm1 to Sm6, the voltage output by the inverter 30 is stopped.

<< 1-4 >> Effect of the first embodiment By the above operation, the current flowing in the winding of the electric motor 7, that is, the value (effective value) of the current flowing in the switches 61 to 63 is controlled by the current shown in FIG. As in the period Pc, control to approach zero (preferably control to make it zero) (hereinafter referred to as "zero current control") can be performed. Therefore, the switching operation of the switching devices 61 to 63 can be performed in a state where no current is flowing through the switching devices 61 to 63, and an arc discharge is not generated between the contacts of the switching devices 61 to 63. Therefore, when a mechanical relay is used as the switches 61 to 63, contact welding can be prevented and a highly reliable electric motor drive device can be realized. Note that the "control to make zero" here does not mean that the value (effective value) of the current flowing through the switches 61 to 63 is made exactly zero, but it is so zero that it can be regarded as substantially zero. It means that it is close to.

However, since it cannot be set to zero accurately, a weak current will flow in the winding of the motor 7. When the switching operations of the switching devices 61 to 63 are performed in this state, for example, assuming the connection state of the switching devices 61 to 63 shown in FIG. 6, for example, the normally closed contact 61b and the common contact 61c are in the connected state. If the normally closed contact 61b and the common contact 61c are operated in the open state in this state, an arc discharge due to an electric current may occur. The arc discharge at that time is slight, but when it comes into contact with the normally open contact 61a in a state where the arc discharge occurs, the normally open contact 61a, the normally closed contact 61b, and the common contact 61c are connected with low impedance. In the zero current control, a voltage is supplied by the inverter 30 in order to cancel the induced voltage of the electric motor 7, and in that state, the normally open contacts 61a to 63a, the normally closed contacts 61b to 63b, and the common contacts 61c to 63c have low impedance. If two or more of the connected states are generated, a short-circuit current is generated, and an excessive current may flow to the switches 61 to 63.

As a method of reducing the drive current supplied to the winding to 0, there is a method of stopping the output of the PWM signals Sm1 to Sm6, but if the output is stopped while a large current is flowing in the winding of the electric motor 7, it will be regenerated. There are concerns about the generation of electric power and surge voltage. However, by stopping the operation of the inverter 30 after performing the zero current control, it is possible to stop the operation of the inverter 30 in a state where the current flowing through the winding of the electric motor 7 is reduced. As a result, it is possible to create a state in which the energy stored in the inductance of the winding of the electric motor 7 is reduced, a regenerative voltage is generated, and the electric motor 7 goes to the capacitor 20 via the connection switching device 60 and the rectifying elements 321 to 326. It is possible to prevent the charging current from flowing. Further, by operating the switches 61 to 63 in this state, the output of the inverter 30 is stopped. Therefore, by switching the switches 61 to 63 during that time, the normally open contacts 61a to 63a and the normally closed contacts 61b to 63b Even when the common contacts 61c to 63c are connected with low impedance, the switching operation can be completed without an excessive current flowing.

Further, if the switching operations of the switches 61 to 63 are performed during the power supply stop period Ps after the current control period Pc has elapsed, the switching can be performed without causing a large current change of the drive current supplied to the winding. .. That is, in the connection switching device 60 of the first embodiment, the first effective value of the alternating current flowing in the winding is closer to zero than the second effective value of the alternating current flowing in the winding before the switching operation of the switching device. It has a first stage having a current control period Pc and a second stage having a power supply stop period for stopping the AC voltage output by the inverter, and during the period of the second stage, the switching operation of the switch is provided. To execute. Here, the second stage is a stage after (for example, immediately after) the first stage. Therefore, sudden changes in the electric motor 7 due to switching can be suppressed, and the connection state can be switched while suppressing noise and vibration of the electric motor 7. However, since the current is not output during the current control period Pc period, the torque for driving the motor 7 is not generated, and the voltage is not applied to the motor 7 even during the power supply stop period Ps, so that the motor 7 is driven. No torque is generated. Therefore, in the case of an air conditioner, the electric motor 7 is decelerated according to the magnitude of the load of the compressor that compresses the refrigerant and the moment of inertia of the compressor. However, the operating time of the switches 61 to 63 is at most about 10 milliseconds. Therefore, if the current control period Pc and the power supply stop period Ps are set sufficiently short, the switching operation can be completed in 100 milliseconds or less at the longest, so that no significant deceleration occurs. That is, the rotation speed of the electric motor 7 is appropriately set according to the load and moment of inertia of the compressor, the current control period Pc and the power supply stop period Ps are appropriately set, or a combination thereof. It is possible to complete the switching operation and continue the rotation without significantly reducing the number. This makes it possible to suppress an increase or decrease in room temperature due to the shutdown of the compressor.

When the electric motor is installed in the compressor, the current control period is 1 second or less, and the power supply stop period is 1 second or less.

Therefore, in the control device 100 of the first embodiment, when the electric motor 7 is rotating at a high speed, the value of the current flowing through the electric motor 7 or the connection switching device 60 (for example, an effective value) is brought close to zero (desirably). Controls (so that it becomes substantially 0), and after confirming that the current has become sufficiently zero, it operates to stop the energization of the inverter 30. It is controlled so that the switching operations of the switching devices 61 to 63 of the connection switching device 60 are performed while the power supply of the inverter 30 is stopped. When the current flowing through the winding of the electric motor 7 is extremely low (light load state), the inverter 30 may be operated so as to stop energization without performing zero current control. By doing so, it is possible to suppress the generation of noise and vibration due to the change in the current during the switching operation of the switches 61 to 63. Further, when a mechanical relay is used for the connection switching device 60, it is possible to prevent failures such as contact welding, and a highly reliable electric motor drive device can be obtained.

In other words, the electric motor drive device 2 of the first embodiment is a product because the failure occurrence rate can be reduced and the life of the device can be extended even when the connection switching device 60 is configured with inexpensive parts. The cost can be reduced.

Since the current value at which irreversible demagnetization occurs differs between the Y connection and the Δ connection, protection corresponding to each winding is possible by switching the protection level at the timing of switching between the Y connection and the Δ connection. However, when a mechanical relay is used, after a current flows through the exciting coils 611, 621, 631, the switches 61, 62, 63 have the normally open contacts 61a, 62a, 63ba, or the normally closed contacts 61b, 62b, 63b. There will be a time delay before switching to. Therefore, for example, when switching from Y connection to delta connection, the protection level is switched to delta connection, but it is assumed that the motor 7 is still in the state of Y connection because it is in the process of switching to delta connection. Will be done. In that case, if an excessive current flows by mistake, irreversible demagnetization of the electric motor 7 may occur.

Therefore, when switching the connection, when the control to reduce the current to zero is started, or when the control to set the current to zero is started and the operation of the inverter 30 is stopped until the connection is switched, the Y connection having a low protection level is used. By setting the protection level, it is possible to protect from irreversible demagnetization regardless of whether the connection is Y or Δ when the connection is switched. Needless to say, since the current is controlled to be zero when the connection is switched, there is no effect on the operation of the electric motor 7.

As for the protection level, as described above, the magnetic force in the initial state of the motor 7 is set to 100%, and the current value (for example, the magnetic force) is within a range that does not affect the performance when irreversible demagnetization occurs. (Current value that drops to 97%) can be set, and by setting the current value in Δ connection to √3 times the value of Y connection, it is surely protected from irreversible demagnetization regardless of the connection state. It becomes possible to do. However, in the case of detecting the current value flowing through the winding and performing protection without detecting _{I Δ} in FIG. 8 (b), the _{current value of I Δ} ÷ √3 (the current value of the protection level in the Y connection). It is desirable to set (equivalent to) as the protection level. There is no problem even if the set current value of the protection level is changed according to the equipment to be used.

<< 1-5 >> Modification example of the first embodiment A diode or the like is generally used as the rectifying elements 11 to 14 of the rectifying circuit 10. However, the configuration of the rectifier circuit 10 is not limited to the example of FIG. For example, instead of the rectifying elements 11 to 14 of the rectifier circuit 10, a transistor element (semiconductor switch) such as a MOSFET (Metal-Oxide-Semiconductor Field-Effective-Transistor) is used, and the voltage supplied from the AC power supply 4 It may be configured to perform rectification by turning it on according to the polarity of (input AC voltage).

IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs are used as the switching elements 311 to 316 of the inverter main circuit 310, but the present invention is not limited thereto. As the switching elements 311 to 316, any elements that can perform switching may be used. When MOSFETs are used as switching elements 311 to 316, it is not necessary to connect rectifying elements 321 to 326 (FIG. 5) for circulation in parallel because the MOSFET has a parasitic diode due to its structure.

The materials constituting the rectifying elements 11 to 14 and the switching elements 311 to 316 are not only silicon (Si) but also silicon carbide (SiC), gallium nitride (GaN), diamond, etc., which are wide bandgap semiconductors. It is possible to reduce the loss by configuring with.

<< 2 >> Embodiment 2.
The electric motor drive device according to the second embodiment of the present invention is different from the electric motor drive device according to the first embodiment in that the connection switching device 260 is used instead of the connection switching device 60. In the configuration of FIG. 4, the changeover switches 61 to 63 of the connection changeover device 60 use changeover switches (selection switches). In the second embodiment, each switch of the connection switching device 260 is composed of a combination of a normally closed switch and a normally opened switch, that is, a combination of an on / off type switch.

FIG. 12 is a wiring diagram showing the windings 71 to 73 of the electric motor 7 and the connection switching device 260 according to the second embodiment. In the connection changeover device 260 of FIG. 12, the changeover device 61 is composed of a combination of the normally closed switch 615 and the normally open switch 616, and the changeover 62 is composed of the combination of the normally closed switch 625 and the normally open switch 626 for switching. It is composed of a combination of a normally closed switch 635 and a normally opened switch 636 of the vessel 63.

As shown in FIG. 12, when the normally closed switches 615,625,635 are closed (on) and the normally open switches 616,626,636 are open (off), the winding of the motor 7 is wound. 71 to 73 are in the Y connection state. Contrary to the state shown in the figure, when the normally closed switches 615, 625, 635 are open (off) and the normally open switches 616, 626, 636 are closed (on), the motor is in the Δ connection state. Is.

As shown in FIG. 12, even when each switch is configured by a combination of the normally closed switches 615, 625, 635 and the normally open switches 616, 626, 636, an electromagnetic contactor can be used as each switch. it can. An electromagnetic contactor is suitable because it has a small conduction loss when it is turned on.

As shown in FIG. 12, each switch may be configured by using a semiconductor switch. FIG. 13 is a circuit diagram showing a configuration example in which a MOS transistor is used for the switch 61 (62, 63) of the connection switching device 260 of FIG. FIG. 13 shows one of the switches 61, 62, 63. The switches 61, 62, and 63 have the same configuration as each other and operate in the same manner. FIG. 14 is a diagram showing an example of an on / off state of the MOS transistor of the switch of FIG. 13 in tabular form.

As shown in FIG. 13, the switch 61 (62, 63) is a MOS transistor 616a (626a, 626a,) connected in series between the lead wire 61e (62e, 63e) and the output wire 332 (333,331). MOS transistors 616b (626b, 636b) and diodes 616d (626a, 636b) and diodes 616b (626b, 636b) connected in series between the lead wires 61e (62e, 63e) and the output lines 332 (333,331), and the diodes 616c (626c, 636c) and the diodes 616c (626c, 636c). 626d, 636d) and.

Further, the switch 61 (62, 63) includes a MOS transistor 615a (625a, 635a) and a diode 615c (625c, 635c) connected in series between the lead wire 61e (62e, 63e) and the neutral point node 64. ), A MOS transistor 615b (625b, 635b) and a diode 615d (625d, 635d) connected in series between the lead wire 61e (62e, 63e) and the neutral point node 64.

In each MOS transistor 616a (626a, 636a), 616b (626b, 636b), 615a (625a, 635a), 615b (625b, 635b), the anode is connected to the diode and the cathode is the lead wire (or neutral point node or It has a parasitic diode connected to the output line).

As shown in FIG. 14, MOS transistors 616a, 626a, 636a are turned on, MOS transistors 616b, 626b, 636b are turned on, MOS transistors 615a, 625a, 635a are turned off, and MOS transistors 615b, 625b, 635b are turned off. The windings 71 to 73 can be connected by Δ.

Further, as shown in FIG. 14, the MOS transistors 616a, 626a, 636a are turned off, the MOS transistors 616b, 626b, 636b are turned off, the MOS transistors 615a, 625a, 635a are turned on, and the MOS transistors 615b, 625b, 635b are turned on. By turning on, the windings 71 to 73 can be Y-connected.

Further, it is desirable that the MOS transistor as a semiconductor switch is composed of a wide bandgap (WBG) semiconductor. The WBG semiconductor is, for example, a semiconductor containing silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga2O3), and diamond as constituent materials. When composed of a WBG semiconductor, the on-resistance is small, the loss is low, the element heat generation is small, and the switching operation can be performed quickly.

Even when a semiconductor switch is used in this way, it is possible to operate the switching operation at high speed, but the operation variation of about several μs occurs in each semiconductor switch. Therefore, when the time constant L ÷ R based on the winding resistance R and the winding inductance L of the electric motor 7 is very small, a sudden current change occurs and a sudden change in the rotation speed of the electric motor 7 occurs, causing vibration and vibration. Not only may noise be generated, but the semiconductor may generate heat and fail.

Therefore, in the connection switching device 260 made of a semiconductor, the normally closed switch 615, 625, 635 and the normally open switch 616, 626, 636 are switched within the power supply stop period Ps after the current control period Pc shown in FIG. By performing the operation, it is possible to perform the switching operation of the connection state without causing a large current change. Therefore, it is possible to suppress a sudden change in the rotation speed of the electric motor 7 due to the switching operation in the switch. Therefore, the connection state can be switched while suppressing noise and vibration.

Further, when a mechanical relay is used for the connection switching device 260, failures such as contact welding can be prevented, and a highly reliable electric motor drive device can be obtained.

Further, when a semiconductor switch is used for the connection switching device 260, a failure due to heat generation of the semiconductor switch can be prevented, and a highly reliable electric motor drive device can be obtained.

In other words, in the electric motor drive device of the second embodiment, even when the connection switching device 260 is configured with inexpensive parts, the failure occurrence rate can be reduced and the life of the device can be extended, so that the product cost can be extended. Can be reduced.

Except for the above points, the electric motor drive device of the second embodiment is the same as the electric motor drive device 2 of the first embodiment.

<< 3 >> Embodiment 3.
In the first and second embodiments, an example is described in which an electric motor drive device to which the present invention is applied is connected to an electric motor 7 capable of switching windings 71 to 73 between Y connection and delta connection. In the third embodiment, an example is described in which an electric motor drive device to which the present invention is applied is connected to an electric motor 7a capable of switching the number of turns of each of the windings 71 to 73. In the third embodiment, for example, the windings 71 to 73 of each phase are composed of two or more winding portions. In this case, the stator windings 71, 72, 73 are provided by the connection switching device 360 so that both ends of each of the two or more winding portions constituting the windings 71 to 73 of each phase can be connected to the outside of the motor 7a. (In the third embodiment, the number of turns of the winding) is switched. Further, the connection switching device to which the present invention is applied can also be applied to an electric motor capable of switching the winding portion to either parallel connection or series connection.

In FIG. 15, in a Y-connected motor, the windings of each phase are composed of two winding portions, and both ends of the winding portions can be connected to the outside of the motor 7a, and the connection switching device 360 is shown. The configuration for switching the connection status is shown with.

Specifically, the U-phase winding 71 is composed of two winding portions 711 and 712, the V-phase winding 72 is composed of two winding portions 721 and 722, and the W-phase winding 73 is composed of two winding portions 721 and 712. It is composed of two winding portions 731 and 732.

The first end of the winding portion 711,721,731 is connected to the output lines 331, 332, 333 of the inverter 30 via the external terminals 71c, 72c, 73c, respectively. The second ends of the winding portions 711, 721 and 731 are connected to the common contacts of the changeover switches 617, 627 and 627 via the external terminals 71 g, 72 g and 73 g, respectively.

The first end of the winding portion 712,722,732 is connected to the common contact of the changeover switches 618, 628, 638 via the external terminals 71h, 72h, 73h, respectively. The second ends of the winding portions 712, 722 and 732 are connected to the neutral point node 64 via the external terminals 71d, 72d and 73d, respectively.

The normally closed contacts of the changeover switches 617, 627 and 637 are connected to the normally closed contacts of the changeover switches 618, 628 and 638, respectively. The normally open contacts of the changeover switches 617, 627, 637 are connected to the neutral point node 64.

The normally open contacts of the changeover switches 618, 628, 638 are connected to the output lines 331, 332, 333 of the inverter 30.

The connection changeover device 360 is configured by the changeover switches 617, 627, 637, 618, 628, and 638.

Even when such a connection switching device 360 is used, the switching operation of the switching device of the connection switching device 360 is performed during the current control period Pc in the same manner as that shown in the first and second embodiments. It can protect mechanical relays or semiconductor switches.

In the case of the configuration shown in FIG. 15, when the changeover switches 617, 627, 637, 618, 628, and 638 are switched to the normally closed contact side as shown in the drawing, the electric motor 7a is in a series connection state, and the changeover switch 617 is used. , 627, 637, 618, 628, 638 are switched to the normally open contact side opposite to the drawing, and the motor 7a is in a parallel connection state.

Also in the third embodiment, as described in the second embodiment, a combination of the normally closed switch and the normally opened switch can be used instead of the changeover switch. Further, the normally closed switch and the normally opened switch can be used as a semiconductor switch.

The case where the Y-connected motor 7a is switched between the series-connected state and the parallel-connected state has been described above. However, in the Δ-connected motor motor drive device, the series-connected state and the parallel-connected state are switched. The present invention can be applied in the same manner as described above.

In addition, the electric motor drive device of an electric motor having a configuration in which an intermediate tap is provided in the winding in a Y connection or Δ connection and a part of the winding is short-circuited by a switching means to change the voltage required for driving. , The present invention can be applied. In short, the present invention can be applied as long as the electric motor can switch the connection state of the windings and the counter electromotive voltage can be switched by switching the connection state.

Except for the above points, the electric motor drive device of the third embodiment is the same as the electric motor drive device of the first or second embodiment.

Note that the configurations shown in the above embodiments 1 to 3 are configuration examples of the present invention, and can be combined with other known techniques.

2 Electric motor drive device, 4 AC power supply, 7, 7a electric motor, 8 reactor, 10 rectifier circuit, 20 capacitor, 30 inverter, 60, 260, 360 connection switching device, 61-63 switching device, 71-73 winding, 80 control Power generation circuit, 85 bus current detection means, 100 control device, 102 operation control unit, 110 inverter control unit, 900, 900a, 900b refrigeration cycle device, 902 four-way valve, 904 compressor, 906 heat exchanger, 908 expansion valve, 910 Heat exchanger.

Claims (14)

1. A connection switching device having a switching device and switching the connection state of the windings of the motor by performing the switching operation of the switching device during the rotation operation of the motor.
   An inverter in which an AC voltage is applied to the winding through the switch and a counter electromotive voltage is applied from the winding of the electric motor during rotation operation via the switch.
   A control device that controls the rotational operation of the electric motor by controlling the inverter and causes the connection switching device to switch the connection state.
   Have,
   With the first stage having a current control period in which the first effective value of the alternating current flowing through the winding is closer to zero than the second effective value of the alternating current flowing through the winding before the switching operation of the switch. ,
   It is a stage after the first stage, and includes a second stage having a power supply stop period for stopping the AC voltage output by the inverter.
   An electric motor driving device that executes a switching operation of the switching device during the period of the second stage.
2. The motor drive device according to claim 1, wherein in the current control period, the inverter applies an AC voltage to the windings, and a counter electromotive voltage is applied from the windings of the motor.
3. Further provided with a current detecting means for detecting the current supplied to the inverter,
   The electric motor driving device according to claim 1 or 2, wherein the inverter is controlled based on the current detected by the current detecting means.
4. The motor drive device according to any one of claims 1 to 3, wherein the switching of the connection state is switching between the Y connection and the Δ connection.
5. The electric motor driving device according to any one of claims 1 to 4, wherein the switching of the connection state is switching of the number of turns of the winding.
6. The switch has an electromagnetic contactor and
   The magnetic contactor has an exciting coil and contacts driven by a current flowing through the exciting coil.
   The electric motor driving device according to any one of claims 1 to 5, which controls a current supplied to the exciting coil.
7. The switch has a semiconductor switch controlled by a signal input to a control terminal.
   The electric motor driving device according to any one of claims 1 to 5, which controls a signal input to the control terminal.
8. The electric motor drive device according to claim 7, wherein the semiconductor switch is made of a wide bandgap semiconductor.
9. The electric motor is provided in the compressor.
   The electric motor driving device according to any one of claims 1 to 8, wherein the current control period is 1 second or less.
10. The electric motor is provided in the compressor.
    The electric motor drive device according to any one of claims 1 to 8, wherein the power supply stop period is 1 second or less.
11. A refrigeration cycle device including the electric motor drive device according to any one of claims 1 to 10.
12. An air conditioner including the refrigeration cycle device according to claim 11.
13. A water heater including the refrigeration cycle device according to claim 11.
14. A refrigerator provided with the refrigeration cycle device according to claim 11.

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