JP2015201933A - Single-phase induction motor controller and air conditioner using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller for a single-phase induction motor that safely performs the switching operation from an operation based on a commercial power source to an operation based on an inverter without temporarily stopping a motor.SOLUTION: A controller for a single-phase induction motor has an inverter 5 for applying to a primary winding 7 and an auxiliary winding 8 an AC voltage having a frequency which is not more than a commercial power source frequency, first opening/closing parts (SW1a, SW1b) connected so as to form a closed circuit together with a commercial power source 1 and the primary winding 7, and a second opening/closing part (SW2) connected to the commercial power source 1 and the auxiliary winding 8 in series so as to form a closed circuit together with the commercial power source 1 and the auxiliary winding 8. When a first driving mode in which the opening/closing parts are set to ON-state, the inverter 5 is set to OFF-state, and a single-phase induction motor 9 is driven by the commercial power source 1 is switched to a second driving mode in which the opening/closing parts are set to ON and the single-phase induction motor 9 is driven by the inverter 5, the inverter 5 is kept to OFF-state while the contact points of the opening/closing parts are set to ON-state.

Description

  The present invention relates to a control device that drives an induction motor by switching between an inverter and a commercial power source, and an air conditioner using the same.

  Conventionally, as an induction motor control device that operates an induction motor by selectively switching between an inverter and a commercial power source, a plurality of inverters, phase-advanced capacitors, induction motors connected to the commercial power source and a connection between them are switched. And a switching prohibiting means (regenerative power detection circuit for prohibiting operation by the inverter while the regenerative power is being detected) and detecting means for detecting the regenerative power when the induction motor is free running ) And a capacitor connection means for connecting a phase advance capacitor to the induction motor after the operation is stopped by the inverter and before the operation is started by the commercial power source and after the operation is stopped by the commercial power source and before the operation is started by the inverter. Is known (see, for example, Patent Document 1).

  FIG. 6 shows the configuration of a conventional induction motor control device described in Patent Document 1. In FIG.

  A conventional control device 101 shown in FIG. 6 is connected to the commercial power source 1 and supplies power to the induction motor M, and includes an inverter 102 supplied with power from the commercial power source 1.

  In the control device 101, the output terminal Yb is connected to the power supply terminal Ya connected to the commercial power supply 1 through the coil of the electromagnetic contactor MC and the first contact m11.

  Further, a phase advance capacitor 103 is connected to a connection point between the first contact m11 and the output terminal Yb via a second contact m21 which is a capacitor connection means.

  The primary side of the inverter is connected to the connection point between the coil of the magnetic contactor MC and the first contact m11, and the secondary side of the inverter is connected to the output terminal Yb via the third contact m31.

  An induction motor M is connected to the output terminal Yb of the control device 101 via a thermal relay Th.

  FIG. 7 is a diagram showing the control timing of each contact in the conventional induction motor control device described in Patent Document 1. In FIG.

  As shown in FIG. 7, when the control apparatus 101 operates the induction motor M with the inverter 102, the first contact m11 and the second contact m21 are off, and the third contact m31 is turned on. To do.

  Next, when the induction motor M is operated by the commercial power source, the first contact m31 is turned off, the second contact m21 is turned on, and the phase advance capacitor 103 is connected. The contact m11 is turned on.

Thereafter, when switching to the operation by the inverter 102 again, the first contact m11 is first turned off to stop the operation by the commercial power supply, and then the regenerative power of the induction motor M that continues to rotate by free run is detected as a regenerative power detection circuit (FIG. (Not shown), the second contact m21 is turned off, the phase advance capacitor 103 is disconnected, and after a fixed period of time,
The third contact m31 is turned on to restart the operation by the inverter.

JP-A-5-300789

  However, in the induction motor control device described in Patent Document 1, when the contact (m11, m21, m31 in FIG. 6) of the switching part for switching between the operation by the commercial power supply and the operation by the inverter is abnormal or when bounce occurs In such a case, for example, when switching from the commercial power supply to the inverter operation is performed when the contact of the switching unit is in the on state at the timing when it should be originally off. There is a problem that an alternating voltage from a commercial power supply is short-circuited through the inverter and a large current flows through the inverter.

  Furthermore, when the conventional induction motor control device is used as a drive device for an air conditioner compressor or the like, generally, the induction motor that drives the compressor is in a free-run state after being in a non-energized state. Since the duration to continue is extremely short, when switching from operation using a commercial power supply to operation using an inverter, the compressor stops while the operation of the inverter is stopped until no regenerative power is detected.

  When the operation of the compressor of the air conditioner is stopped, since the pressure difference (high-low pressure difference) between the suction pressure (low-pressure side) and the discharge pressure (high-pressure side) of the compressor stops in a large state, the compressor The load torque of the electric motor required for restarting the motor becomes very large. As a result, since the starting torque of the electric motor is insufficient, there are operational restrictions such as the compressor cannot be restarted until the difference between the high and low pressures of the compressor is solved to some extent.

  As described above, when the conventional induction motor control device is used as a drive device for an air conditioner compressor, there is no particular problem in an application in which a commercial power source is used as a backup in case of inverter failure. In applications where commercial power supply operation and inverter operation are continuously switched according to the size of the load, the conventional method of temporarily stopping the compressor when switching operation reduces the indoor temperature fluctuation. There arises a problem that it is impossible to enjoy the merits of the original inverter air conditioner that suppresses the air conditioning control with less temperature unevenness.

  The present invention solves the above-described conventional problems, and an induction motor control apparatus capable of switching between operation by a commercial power source and operation by an inverter safely without stopping the induction motor, and It aims at providing the used air conditioner.

In order to solve the above-described conventional problems, a control device for a single-phase induction motor according to the present invention obtains power supply from a DC output of a rectifier circuit that rectifies an AC voltage from a commercial power source into a DC, and An inverter that applies an AC voltage having a frequency lower than the commercial power supply frequency to either the main winding or the auxiliary winding and a commercial power supply and the main winding are connected to form a closed circuit. The first open / close unit and the phase advance capacitor and the second open / close unit connected in series so as to form a closed circuit with the commercial power source and the auxiliary winding when the first open / close unit is turned on. A first drive mode in which the first open / close unit and the second open / close unit are both turned on, and the inverter is turned off, and the single-phase induction motor is rotationally controlled by a commercial power source, Or first The open / close unit and the second open / close unit are both turned off, and the inverter selects either one of the second drive modes in which the single-phase induction motor is rotationally controlled by the inverter, and the single-phase induction motor is Control rotation.

  Furthermore, the control device for a single-phase induction motor according to the present invention includes an opening / closing part contact detection unit that detects an opening / closing state of the contacts of the first opening / closing part and the second opening / closing part, and the second drive unit from the first drive mode to the second. When the drive mode is switched to the drive mode, the inverter is kept in the off state while it is detected that the contact of at least one of the opening / closing sections is in the on state.

  Thereby, when switching from the first drive mode (operation by commercial power supply) to the second drive mode (operation by inverter), a contact abnormality that does not turn off at the contact point of the first opening / closing part or the second opening / closing part, Since the operation by the inverter is not started during the period when the contact bounce that repeats the ON and OFF states occurs, it is possible to surely prevent the AC voltage from the commercial power supply from being short-circuited through the legs constituting the inverter. it can.

  In addition, the control device for the single-phase induction motor is provided, and the compressor of the air conditioner is driven by the single-phase induction motor, so that the first drive mode (operation by a commercial power source) is changed to the second drive mode (inverter). Since the non-energization period to the single-phase induction motor, which occurs when the mode is switched to (operating by), can be suppressed to a time (about 10 ms to 40 ms) or less enough to confirm the end of the contact bounce of the switching unit. The operation from the commercial power source can be switched to the operation by the inverter safely and promptly without stopping the compressor.

  When switching from commercial power supply operation to inverter operation, it is possible to prevent the inverter from switching to inverter operation while the contact of the switch is on, so operation by the inverter is started during contact failure or contact bounce of the switch Thus, it is possible to reliably prevent a situation in which a large short-circuit current flows from the commercial power supply via the inverter.

  In addition, when driving a compressor of an air conditioner using this single-phase induction motor control device, commercial operation is performed when the induction motor is driven at high speed such as during rated operation, and the induction motor is operated at low speed such as during light loads. By switching to the inverter operation when driving at, it is possible to keep the capacity of the inverter required for variable speed control of the induction motor low.

The figure which shows the circuit structural example of the control apparatus of the single phase induction motor in Embodiment 1 of this invention The figure which shows an example of the concrete circuit structure of the switching part contact state detection part 13 in Embodiment 1. FIG. The figure which shows the timing regarding the voltage applied to the switching part contact state detection part 13 in Embodiment 1, an output signal, and the output permission determination result of the inverter 5 in a control part. The figure which shows another circuit structural example of the control apparatus of the single phase induction motor in Embodiment 1 The figure which shows the circuit structural example of the control apparatus of the single phase induction motor in Embodiment 2 The figure which shows the circuit structure of the control apparatus of the conventional induction motor The figure which shows the operation | movement timing of the 1st-3rd contact and the induction motor in the control apparatus of the conventional induction motor.

According to a first aspect of the present invention, there is provided a single-phase induction motor having a stator winding composed of a main winding and an auxiliary winding, a rectifying circuit for rectifying an AC voltage from a commercial power source into a DC, and a DC output of the rectifying circuit. An inverter that obtains power supply and applies an AC voltage having a frequency lower than the commercial power supply frequency to either the main winding or the auxiliary winding of the single-phase induction motor; the commercial power supply and the main winding; A first open / close unit comprising at least one open / close means connected so as to form a closed circuit together with the commercial power supply and the auxiliary winding when the first open / close unit is turned on. A phase advance capacitor and a second opening / closing part connected in series with each other, the first opening / closing part and the second opening / closing part are both turned on, and the inverter is turned off. , The commercial power supply A first drive mode for controlling the rotation of the phase induction motor, or a second drive mode for controlling the rotation of the single-phase induction motor by the inverter with both the first opening / closing section and the second opening / closing section turned off. A control device that selects one of the drive modes and controls the rotation of the single-phase induction motor, and detects the open / close state of the contact points of the first open / close unit and the second open / close unit. And when the drive mode is switched from the first drive mode to the second drive mode, the inverter is turned on while it is detected that the contact point of at least one of the opening / closing parts is on. By maintaining the switch in the OFF state, the drive by the inverter is opened during contact anomalies where the contact of the first switching unit or the second switching unit does not enter the OFF state or contact bounce that repeats the ON and OFF states. Since it does not, can be an AC voltage from the commercial power supply is reliably prevented from being short-circuited via the inverter.

  In addition, the period of time when the end of the contact bounce in the first and second switching parts can be confirmed during the non-energization period to the single-phase induction motor when the mode is switched from the first drive mode to the second drive mode ( Therefore, it is possible to switch from operation using a commercial power source to operation using an inverter safely and quickly.

  In the second invention, in particular, the rectifier circuit in the first invention is a voltage doubler rectifier circuit, and one end of a main winding or an auxiliary winding driven by an inverter and a midpoint potential portion of the voltage doubler rectifier circuit are provided. Since it is always connected and an inverter can be realized with a smaller number of legs than in the first invention, a cheaper configuration can be achieved.

  In particular, the third aspect of the invention includes the control device for the single-phase induction motor of the first or second aspect of the invention, and drives the compressor by the single-phase induction motor. In the first drive mode, the compressor can be driven by a commercial power supply without using an inverter, and the compressor can be driven by the inverter only during light loads. Unlike conventional inverter air conditioners, it does not require an inverter capacity that can handle loads exceeding the rated frequency. Therefore, the inverter capacity can be reduced compared to conventional inverter air conditioners, and an inexpensive configuration can be achieved. Become.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a diagram showing a configuration of a control device for a single-phase induction motor according to a first embodiment of the present invention.

  As shown in FIG. 1, the control device in the present embodiment includes a rectifier circuit 3 connected to a commercial power source 1 via a reactor 2 in order to rectify an AC voltage from a single-phase commercial power source 1 into a direct current, A smoothing capacitor 4 connected to the output terminal of the rectifier circuit 3 and a voltage type inverter 5 connected to the output terminal of the rectifier circuit 3 are provided.

  The inverter 5 includes two legs (a first leg 6a and a second leg 6b), and a main winding 7 and an auxiliary winding 8 which are arranged in an electrical relationship of about 90 degrees with each other as a stator winding. As a load.

  Each leg (6a, 6b) of the inverter 5 is composed of upper and lower arms each made up of two switching elements connected in series, and a control unit 10 that generates a drive signal for each leg of the inverter 5; A driver circuit 11 is provided for turning on and off the upper and lower arm switches of each leg of the inverter 5 in response to a drive signal from the unit 10.

  Further, the control device for the single-phase induction motor according to the present embodiment includes a closed circuit (commercial power source 1-first opening / closing means SW1a-main winding 7-second opening / closing together with the commercial power source 1 and the main winding 7). Means SW1b-commercial power supply 1), the first open / close sections (first open / close means SW1a and second open / close means) connected between both lines of the commercial power supply 1 and both ends of the main winding 7, respectively. SW1b) and a closed circuit (commercial power source 1-first opening / closing means SW1a-auxiliary winding 8-phase advance capacitor 12-) together with the commercial power source 1, auxiliary winding 8 and first opening / closing portion (SW1a). A second opening / closing part (third opening / closing means SW2) connected in series with the phase advance capacitor 12 is provided so as to form a third opening / closing means SW2-commercial power source 1).

  The first opening / closing part (SW1a, SW1b) and the second opening / closing part (SW2) include a contact state detection unit (contact state detection unit 13a, contact state detection unit 13b, A contact state detection unit 13c) is provided, and the control unit 10 determines the contact state of the opening / closing unit based on detection signals from the contact state detection units (13a, 13b, 13c).

  The control device for a single-phase induction motor of the present invention has the following two modes as drive modes of the single-phase induction motor 9 that is a load. As for the selection method of the drive mode, the user of the control device may instruct the drive mode from the outside with a remote controller or the like, or the drive mode is automatically selected by the control unit 10 or the like based on a change in some load condition. It doesn't matter.

  The first drive mode is a mode in which the single-phase induction motor 9 is driven by the commercial power source 1 and all the first opening / closing parts (SW1a, SW1b) and the second opening / closing part (SW2) are controlled to be in the ON state. Thus, an AC voltage from the commercial power source 1 is applied to the main winding 7, and an AC voltage from the commercial power source 1 is applied to the auxiliary winding 8 via the phase advance capacitor 12. A single-phase induction motor 9 is driven as a so-called capacitor run motor by flowing a current having a phase advanced about 90 degrees electrically with respect to the line 7.

  The second drive mode is a mode in which the single-phase induction motor 9 is a pure single-phase induction motor and is driven by the inverter 5, and all of the first opening / closing parts (SW1a, SW1b) and the second opening / closing part (SW2) are used. After controlling to the off state, the control unit 10 generates a drive signal for each leg (6a, 6b) of the inverter 5, and turns on the upper and lower arms in each leg (6a, 6b) of the inverter 5 via the driver circuit 11. -The single-phase induction motor 9 is rotationally controlled by being driven off.

  As shown in FIG. 1, the inverter 5 forms an H bridge with the first leg 6 a and the second leg, obtains DC power supply from the rectifier circuit 3, and the main winding of the single-phase induction motor 9. 7, an AC voltage having a frequency lower than the power supply frequency of the commercial power supply 1 is applied.

  As for the control method of the inverter 5, the magnitude of the applied AC voltage is approximately proportional to the drive frequency of the inverter 5 so that the excitation current of the main winding becomes substantially equal regardless of the frequency by V / f control or the like. Control.

  Below, an example of the output voltage pattern to each leg (6a, 6b) of the inverter 5 is shown as an example in the case of performing V / f control. Needless to say, the actual output voltage to each leg is controlled by duty adjustment of PWM control according to the DC voltage (Vdc).

Output potential of the leg (6a) = Vdc / 2
Output potential of the leg (6b) = Vdc / 2 + √2Vm · sin ωt
Where Vm: applied voltage (effective value) to main winding, Va: applied voltage (effective value) to auxiliary winding, ω: driving frequency (= 2π × driving frequency), t: time

  In general, in order to drive the single-phase induction motor 9 using the inverter 5 at the same frequency as the operation frequency (referred to as f1) in the first drive mode (operation by the commercial power source), the rated AC of the commercial power source 1 is used. A DC voltage corresponding to the voltage peak is required.

  Therefore, of the two legs (6a, 6b) constituting the inverter 5, the lower arm of the leg (phase) on the side with the lower output potential is beta-on to adjust the output potential of the other leg. By adopting a modulation method such as two-phase modulation, it is possible to increase the AC voltage that can be applied to the main winding 7 (or the auxiliary winding 8) under the same DC voltage condition.

  When the single-phase induction motor 9 is driven as a pure single-phase induction motor, the output torque becomes zero and the motor cannot be started in the stopped state (slip 1 state). To switch the single-phase induction motor 9 to the second drive mode (operation using a pure single-phase inverter) without stopping after the single-phase induction motor 9 is started in the first drive mode (operation using the commercial power source 1) Thus, there is no fear that the output torque becomes zero, and it is possible to continue to drive the single-phase induction motor 9 that is a load.

  FIG. 2 is a diagram showing an example of a specific circuit configuration of the switching unit contact state detection unit 13 in the control device for a single-phase induction motor of the present invention.

  In FIG. 2, only the detection means of the opening / closing part (SW1b) is described, and the description of the circuit part related to the opening / closing parts (SW1a and SW2) is omitted for easy viewing.

  As shown in FIG. 2, the contact state detection unit 13 of the switching unit includes a photocoupler PC1, a current limiting resistor R1, and a load resistor R2 connected to the secondary side of the photocoupler PC1, and includes a commercial power supply. 1 and the primary side of the photocoupler PC1 are connected to both ends of a series circuit with a switching circuit (SW1b in FIG. 2) that detects a contact state via a current limiting resistor R1. The secondary side is connected to the control unit 10, and the control unit 10 determines the open / close state of the contact of the corresponding open / close unit based on the detection signal from the open / close unit contact state detection unit 13, and determines the output permission of the inverter 5. Do.

  FIG. 3 is a diagram showing the voltage applied to the switching unit contact state detection unit 13, the output signal, and the timing of the output permission determination result of the inverter 5 in the control unit 10 in the control device for the single phase induction motor of the present invention. is there.

  As shown in FIG. 3A, the voltage applied to the primary side of the switching unit contact state detection unit 13 is the commercial power source 1 when the contact of the switching unit is on because the inverter 5 is off. When the contact is off, it is zero (no potential difference).

  Further, as shown in FIG. 3B, the detection signal of the switching unit contact state detection unit 13 is such that the absolute value of the voltage applied to the primary side of the switching unit contact state detection unit 13 is a threshold voltage (Vth in the figure). In the following cases (such as point P0 in the figure), the output is H, and in other cases, the output is L.

At time t1 in the figure, the control unit 10 receives a request for transition from the first drive mode (commercial operation) to the second drive mode (inverter operation), and all the opening / closing means (SW1a, SW1b, SW2). Is turned off with a little delay (point P1 in the figure).

  When contact bounce occurs in the relay constituting the switching part, the above detection voltage once becomes H output when the contact is once turned off (point P1 in the figure), but the contact is turned on again. At that time (point P2 in the figure), the output becomes L again.

  As shown in FIG. 3 (C), the control unit 10 outputs the H output for a predetermined time T1 or more after the detection signal from the switching unit contact state detection unit 13 is the L output and after the L output becomes the H output. About the period until it continues, it determines with inverter output prohibition and the inverter 5 is kept off. The time T1 is set to about 1/2 to 2 power cycles of the commercial power source 1 in consideration of the bounce time of the relay or the like constituting the opening / closing unit (approximately 10 ms to 40 ms, equivalent to or twice the bounce time). The

  As a result, at the time (time t2) when the time T1 has elapsed from the time (P3 in the figure) when the relays constituting the opening / closing unit (SW1b, etc.) are completely turned off, the control unit 10 determines that the inverter output is permitted. Then, the inverter operation that is the second drive mode is started.

  For the sake of simplicity, only one switching unit contact state detection unit 13 is shown in the figure, but actually, the detection signals from all the switching unit contact state detection units (13a, 13b, 13c) are confirmed. If there is at least one switching unit that is determined to be prohibited from inverter output, even if the operation in the second driving mode is selected, the driving of the inverter 5 is not started immediately, and all switching unit contact states The drive of the inverter 5 is started after the inverter output permission determination is obtained by the control unit 10 based on the detection signal from the detection unit 13.

  That is, when the control device for the single-phase induction motor according to the present embodiment shifts from the first drive mode by the commercial power source 1 to the second drive mode by the inverter 5, the inverter 5 is kept off while keeping the inverter 5 off. The first opening / closing section (SW1a, SW1b) and the second opening / closing section (SW2) are turned off, and the output signal from the contact state detection section 13 becomes H output for a predetermined time T1 or more after the output signal changes from L output to H output. Energization of the inverter 5 is started after confirming that the state is continued.

  Even when the regenerative voltage from the induction motor is higher than the DC voltage of the smoothing capacitor 4 when turning the first open / close unit and the second open / close unit off from on, smoothing is performed via the diode in the inverter 5. Since the current flows in the direction of charging the capacitor 4 and the energy stored in the winding of the single-phase induction motor 9 can be safely absorbed, the second drive by the inverter 5 from the first drive mode by the commercial power source 1 can be performed. When switching to the drive mode, it is possible to avoid applying a high voltage to the open / close section.

  Conversely, when shifting from the drive mode by the inverter 5 to the drive mode by the commercial power supply 1, the inverter 5 may be turned off first, and then the first opening and closing unit may be turned on. At this time, only when the drive signal of the inverter 5 is turned off, only when the inverter 5 is turned off so that the first and second opening / closing sections (SW1a, SW1b, SW2) can be turned on only when the drive signals of the inverter 5 are all turned off. If the circuit configuration (not shown) enables the power supply for driving the first opening / closing section (SW1a, SW1b) and the second opening / closing section (SW2), the safety may be further increased.

  FIG. 4 is a diagram showing another circuit configuration of the control device for the single-phase induction motor according to the present embodiment.

  The difference from the control device of FIG. 1 described above is that the position of the second opening / closing section (SW2) is the first opening / closing section (SW1b) in the closed circuit path including the commercial power source 1 and the auxiliary winding 8. It is only the form that added.

  Since the first opening / closing part (SW1b) and the second opening / closing part (SW2) are controlled in the opening / closing state almost simultaneously, the operation is the same as in the configuration of FIG. .

  In addition, if the control device for a single-phase induction motor according to the present embodiment is used for driving a compressor of an air conditioner, a compressor driven by a commercial power source and an inverter across an off period of about the bounce time of an opening / closing unit The compressor can be safely switched without stopping the compressor.

  The drive mode selection method includes, for example, a temperature detection means for detecting a room temperature and a target temperature setting means, and the difference between the set target temperature and the room temperature detected by the temperature detection means. A drive mode selection unit (not shown) for selecting either the first drive mode or the second drive mode based on the size, and when the room temperature is away from the target temperature, When the first driving mode is selected and the room temperature approaches the target temperature, the second driving mode may be selected.

  Inverter air conditioners usually require an inverter capacity corresponding to a load of a rated frequency or higher. However, as in the present invention, a single-phase induction motor 9 is used as a motor for driving a compressor, and the vicinity of the rated operation is used. During the operation, the first and second opening / closing sections are turned on and the single-phase induction motor 9 is driven by the commercial power source 1 (first driving mode), and the air conditioning load is stabilized when the room temperature approaches the target temperature and becomes stable Is lighter, the first and second opening / closing sections are turned off and the compressor can be driven by the inverter 5 (second drive mode), so that the inverter capacity can be kept small compared to the conventional inverter air conditioner. Therefore, an inexpensive configuration can be obtained.

  In a separate type air conditioner composed of an indoor unit and an outdoor unit, an inverter 5 that controls a single-phase induction motor 9 that drives a compressor provided in the outdoor unit is provided in the indoor unit. Therefore, the microcomputer that is the control device of the inverter 5, the relay that constitutes the switching means, the DC power source that drives the microcomputer / relay, etc. can be shared with the circuit on the indoor unit side, and must be newly provided on the outdoor unit side Therefore, it is possible to make the structure cheaper.

(Embodiment 2)
FIG. 6 is a diagram showing a circuit configuration of a control device for a single-phase induction motor according to the second embodiment of the present invention.

  As shown in FIG. 6, in the control device for a single-phase induction motor according to the present invention, the rectifier circuit portion in the circuit configuration of the first embodiment is a so-called voltage doubler rectifier circuit, and the voltage doubler capacitors 4a and 4b A connection point (middle point potential) is connected to the main winding 7 of the single-phase induction motor 9.

  As shown in FIG. 6, the inverter 5 is composed of only one leg, and by using a voltage doubler rectifier circuit, the inverter 5 has an effective value of the AC voltage of the commercial power supply 1 as Vac and is close to √2 · Vac. Since a DC voltage is supplied, it is possible to apply an AC voltage up to the maximum Vac across the main winding 7 with the middle point of the voltage doubler capacitors (4a, 4b) as a reference.

  As described above, the control device for the induction motor according to the present embodiment can further simplify the configuration of the inverter 5 by using the voltage doubler rectifier circuit.

In the present embodiment, the winding to which the AC voltage is applied by the inverter 5 is the main winding 7.
However, it goes without saying that the same effect can be obtained even if the auxiliary winding 8 is used instead of the main winding 7.

  As described above, the control device for a single-phase induction motor according to the present invention realizes variable speed control of an induction motor that drives a load using a small-capacity inverter with a simple configuration, and is an air conditioner. It can be applied to electric appliances that are powered by a single-phase AC power source such as a heat pump water heater, a refrigerator, and a washing machine.

DESCRIPTION OF SYMBOLS 1 Commercial power supply 2 Reactor 3 Rectifier circuit 5 Inverter 6a 1st leg 6b 2nd leg 7 Main winding 8 Auxiliary winding 9 Single phase induction motor 10 Control part 12 Phase advance capacitor 13a, 13b, 13c Contact state detection part R1 Current limiting resistor R2 Load resistance SW1a First opening / closing means SW1b Second opening / closing means SW2 Third opening / closing means

Claims (3)

A single-phase induction motor with a stator winding consisting of a main winding and an auxiliary winding;
A rectifier circuit for rectifying an alternating voltage from a commercial power source into a direct current;
An inverter that obtains power supply from a DC output of the rectifier circuit and applies an AC voltage having a frequency lower than a commercial power supply frequency to either the main winding or the auxiliary winding of the single-phase induction motor; ,
A first opening / closing portion comprising at least one opening / closing means connected to form a closed circuit together with a commercial power source and the main winding;
A phase advance capacitor and a second switching unit connected in series so as to form a closed circuit together with a commercial power source and the auxiliary winding when the first switching unit is turned on;
A first driving mode in which both the first opening and closing unit and the second opening and closing unit are turned on, and the inverter is turned off, and the single-phase induction motor is rotationally controlled by a commercial power source, or
The first open / close section and the second open / close section are both turned off, and the inverter selects one of the drive modes of the second drive mode for controlling the rotation of the single-phase induction motor, A control device for a single-phase induction motor that controls the rotation of a single-phase induction motor,
When switching the drive mode from the first drive mode to the second drive mode, comprising an open / close unit contact detection unit that detects an open / closed state of the contacts of the first open / close unit and the second open / close unit, The inverter is kept off while at least one of the contact of the first switch and the contact of the second switch is detected to be on. Induction motor controller. The single-phase according to claim 1, wherein the rectifier circuit is a voltage doubler rectifier circuit, and one end of the main winding is always connected to a midpoint potential portion of the voltage doubler rectifier circuit. Induction motor controller. An air conditioner comprising the control device for a single-phase induction motor according to claim 1 or 2 and driving a compressor by the single-phase induction motor.