WO2019163125A1 - Electric motor drive device and refrigeration cycle application apparatus - Google Patents

Abstract

An electric motor drive device comprising: a connection-switching device (60) for switching the connection state of a winding of an electric motor (7); and an inverter (30) for applying an alternating current the frequency and voltage value of which is variable to the electric motor (7). For at least one of the torque current component and the excitation current component obtained by converting a three-phase alternating current flowing to the electric motor (7) to a d-q axis, the inverter is stopped (130) when the amount of the frequency component is greater than when there is no malfunction in the connection-switching device. Thus, a defect in the connection-switching device can be detected, and therefore damage to the electric motor due to overvoltage, demagnetization of the electric motor due to overcurrent, and the like can be prevented.

Description

Electric motor drive device and refrigeration cycle application equipment

The present invention relates to an electric motor drive device and a refrigeration cycle application device including the same.

2. Description of the Related Art Conventionally, there is known an electric motor drive device that includes a connection switching device that switches a stator winding of an electric motor to one of a plurality of different connection states, an inverter that drives the electric motor, and a control unit that controls the inverter. (For example, Patent Document 1).

Patent No. 4619826

In the technique described in Patent Document 1, when switching the winding, the connection switching device is operated. However, if the connection switching device is defective, a sudden voltage or current change occurs, and the motor is damaged due to overvoltage. There is a risk of demagnetizing the motor due to overcurrent.

The present invention has been made in view of the above, and provides a motor drive device that can prevent damage to the motor due to overvoltage, demagnetization of the motor due to overcurrent, and the like even when the connection switching device is defective. The purpose is to do.

The electric motor drive device according to the present invention is
An electric motor drive device for driving an electric motor having three-phase windings,
A connection switching device for switching the connection state of the windings of the motor in response to a switching signal;
An inverter for applying an alternating voltage having a variable frequency and voltage value to the motor;
A current detection unit that detects a three-phase alternating current flowing in the motor; and a three-phase two-phase conversion unit that converts the three-phase alternating current into a torque current component and an excitation current component; and the inverter and the connection switching A control device for controlling the device,
The inverter stops when the amount of harmonic components of at least one of the torque current component and the excitation current component is larger than when there is no failure in the connection switching device.

According to the present invention, it is possible to detect a malfunction of the connection switching device, and therefore it is possible to prevent the motor from being damaged due to overvoltage, the demagnetization of the motor due to overcurrent, and the like.

It is the schematic which shows an example of the refrigerating cycle of an air conditioner. It is a figure 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 coil | winding and connection switching apparatus of the electric motor of FIG. 1 in detail. It is a wiring diagram which shows the detail of the switch of the connection switching apparatus of FIG. (A) And (b) is a figure which shows notionally the coil | winding in the different connection state of an electric motor. 3 is a functional block diagram illustrating an example of a control device used in Embodiment 1. FIG. It is a block diagram which shows the structural example of the voltage command calculating part of FIG. (A) And (b) is a wiring diagram which shows the connection switching apparatus in a failure state. (A) And (b) is a figure which shows the connection state of a coil | winding when connection switching has failed. (A) And (b) is a figure which shows the waveform of an inverter output current when a winding is in the state of Fig.10 (a), and the waveform of an exciting current component and a torque current component. (A) And (b) is a figure which shows the waveform of an inverter output current when a coil | winding is in the state of FIG.10 (b), and the waveform of an exciting current component and a torque current component. It is a block diagram which shows the structural example of the failure detection part 130 of FIG. (A)-(c) shows the figure which showed simply the impedance seen from each phase when a coil | winding is in the state of Fig.10 (a). (A)-(c) shows the figure which showed simply the impedance seen from each phase when a coil | winding is in the state of FIG.10 (b). It is a figure which shows the determination method of the aspect of a failure in Embodiment 1 in a table format. It is a figure which shows the electric motor drive device of Embodiment 2 of this invention. 6 is a functional block diagram illustrating an example of a control device used in Embodiment 2. FIG. It is a figure which shows the electric motor drive device of Embodiment 3 of this invention. FIG. 10 is a wiring diagram showing a current detection element together with a stator winding and a connection switching device of an electric motor in Embodiment 3. FIG. 9 is a functional block diagram illustrating an example of a control device used in a third embodiment. It is a block diagram which shows the structural example of the failure detection part 130c of FIG. (A) And (b) is a figure which shows the connection state of a coil | winding and the electric current which flows into a coil | winding when connection switching has failed in Embodiment 3. FIG. (A) And (b) shows the waveform of the winding current when the winding is in the state of FIG. 23 (a), and the waveform of the winding current when the winding is in the state of FIG. 23 (b). FIG. It is a figure which shows the determination method of the aspect of a failure in Embodiment 3 in a table format. It is a figure which shows the electric motor drive device of Embodiment 4 of this invention.

Hereinafter, an electric motor drive device according to an embodiment of the present invention and a refrigeration cycle application device including the same will be described with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

An example of a refrigeration cycle application device is an air conditioner. In the following embodiments, the present invention is applied to a motor drive device that drives a compressor of an air conditioner.

Initially, the refrigerating cycle in an example of an air conditioner is demonstrated with reference to FIG.
The refrigeration cycle 900 in FIG. 1 can be operated for heating or cooling by switching the four-way valve 902.

During the heating operation, as indicated by solid arrows, the refrigerant is pressurized and sent out by the compressor 904, and passes through 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. Return to the compressor 904. During the cooling operation, as indicated by broken line arrows, the refrigerant is pressurized and sent out by the compressor 904, and passes through 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. Return to the compressor 904.

During the heating operation, the indoor heat exchanger 906 acts as a condenser to release heat, and the outdoor heat exchanger 910 acts as an evaporator to absorb heat. During the cooling operation, the outdoor heat exchanger 910 acts as a condenser to release heat, and the indoor heat exchanger 906 acts as an evaporator to absorb heat. The expansion valve 908 expands the refrigerant by reducing the pressure. The compressor 904 is driven by an electric motor 7 that is controlled at a variable speed.

Embodiment 1 FIG.
FIG. 2 is a schematic wiring diagram showing the electric motor drive device 2 according to the first embodiment of the present invention together with the electric motor 7.
The illustrated electric motor drive device 2 is for driving the electric motor 7, and includes AC power input terminals 3 a and 3 b, a reactor 8, a rectifier circuit 10, a capacitor 20, an inverter 30, and a connection switching device 60. , Control power generation circuit 80, bus current detection means 85, failure indicator 87, and control device 100.

The control device 100 may be configured with, for example, a microcomputer (microcomputer) having a CPU (Central Processing Unit), a DSP (Digital Signal Processor), or the like, or may be configured with dedicated hardware. Below, it demonstrates as what is comprised with the microcomputer.

The AC power input terminals 3a and 3b are connected to an external AC power supply 4, and an AC voltage is applied from the AC power supply 4 to the AC power input terminals 3a and 3b. For example, the applied voltage has an amplitude (effective value) of 100 V, 200 V, and the like, and a frequency of 50 Hz, 60 Hz, or the like.

The rectifier circuit 10 receives AC power from the AC power supply 4 via the input terminals 3 a and 3 b and the reactor 8 and rectifies the AC power. The rectifier circuit 10 is a full-wave rectifier circuit formed by bridge-connecting rectifier elements 11 to 14 such as diodes.

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

As shown in FIG. 3, the inverter 30 includes an inverter main circuit 310 and a drive circuit 350, and an input terminal of the inverter main circuit 310 is connected to the electrode of the capacitor 20.
A 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 referred to as a DC bus.

The inverter 30 is controlled by the control device 100 so that the switching elements 311 to 316 of the six arms of the inverter main circuit 310 are turned on and off to generate a three-phase alternating current having a variable frequency and a variable voltage value. 7 is supplied. Rectifying elements 321 to 326 for reflux are connected in parallel to the switching elements 311 to 316.

The motor 7 is a three-phase permanent magnet synchronous motor, and an end portion of a three-phase stator winding is drawn out of the motor 7 and is either a star connection (Y connection) or a delta connection (Δ connection). Switching to is possible. This switching is performed by the connection switching device 60.

FIG. 4 shows the stator winding and connection switching device 60 of the electric motor 7 in more detail.
As shown in the figure, the first ends 71a, 72a, 73a of the three- phase windings 71, 72, 73 of the electric motor 7 including the U phase, the V phase, and the W phase are external terminals 71c, 72c, 73c, respectively. The second ends 71b, 72b, 73b of the U-phase, V-phase, and W- phase windings 71, 72, and 73 are connected to the external terminals 71d, 72d, and 73d, respectively. Connection is possible. The U-phase, V-phase, and W- phase output lines 331, 332, and 333 of the inverter 30 are connected to the external terminals 71c, 72c, and 73c.

In the illustrated example, the connection switching device 60 includes switchers 61, 62, and 63. As the switching devices 61, 62, 63, electromagnetic contactors whose contacts are electromagnetically opened and closed are used. The electromagnetic contactor includes what is called a relay. The electromagnetic contactor is configured as shown in FIG. 5, for example, and takes different connection states when current is passed through the exciting coils 611, 621, and 631 and when current is not passed.
The exciting coils 611, 621, and 631 are connected so that a current from a switching power supply V60 described later flows when the semiconductor switch 604 is ON. Opening / closing of the semiconductor switch 604 is controlled by a switching signal Sc output from the control device 100.

Note that the switching signal Sc output from the control device 100 may be supplied to the exciting coils 611, 621, 631. This is possible when the control device 100 (for example, configured by a microcomputer) is configured to allow a sufficient current to flow as the signal Sc.

The common contact 61c of the switch 61 is connected to the terminal 71d via the connection line 61e, the normally closed contact 61b is connected to the neutral point node 64, and the normally open contact 61a is the V-phase output line of the inverter 30. 332 is connected.
The common contact 62c of the switch 62 is connected to the terminal 72d via the connection line 62e, the normally closed contact 62b is connected to the neutral point node 64, and the normally open contact 62a is the W-phase output line of the inverter 30. 333.
The common contact 63c of the switch 63 is connected to the terminal 73d through the connection line 63e, the normally closed contact 63b is connected to the neutral point node 64, and the normally open contact 63a is the U-phase output line of the inverter 30. 331.

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

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

Hereinafter, for each of the switching devices 61, 62, and 63, the state switched to the normally closed contact side is referred to as a Y connection switching state, and the state switched to the normally open contact side is referred to as a Δ connection switching state.
The switches 61, 62, and 63 are called U-phase, V-phase, and W-phase switches, respectively.

Here, the advantage of using the motor 7 that can be switched to either Y connection or Δ connection will be described below with reference to FIGS. 6 (a) and 6 (b).

6A shows the connection state of the stator windings 71, 72, and 73 when the Y connection is used, and FIG. 6B shows the connection state of the stator windings 71, 72, and 73 when the Δ connection is used. Each is shown conceptually.
When the line voltage at the Y connection is V _Y , the flowing current is I _Y , the line voltage at the Δ connection is V _Δ , the flowing current is I _Δ, and the voltages applied to the windings of each phase are equal to each other,
V _Δ = V _Y / √3 (1)
At this time,
I _Δ = √3 × I _Y (2)
There is a relationship.

When the voltage V _Y and current I _Y at the Y connection and the voltage V _Δ and current I _Δ at the Δ connection have the relationship of the expressions (1) and (2), the motor is used at the Y connection and the Δ connection. Are supplied with the same power.
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.

Using the above properties, it is conceivable to select the connection state according to the load conditions. For example, it is conceivable to operate at a low speed with a Y connection when the load is low and to operate at a high speed with a Δ connection when the load is high. By doing in this way, the efficiency at the time of a low load can be improved and the high output at the time of a high load is also attained.

Hereinafter, the case of the electric motor that drives the compressor of the air conditioner will be described in more detail.
As an electric motor 7 for driving a compressor of an air conditioner, a synchronous motor using a permanent magnet as a 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 motor 7 is rotated at a high speed to quickly approach the set temperature, and when the room temperature is close to the set temperature, the motor 7 is slowed down. In this case, the proportion of the time that is operated at a low speed is large.

When using a synchronous motor, the counter electromotive force increases as the rotational speed increases, and the voltage required for driving increases. As described above, the counter electromotive force is higher in the Y connection than in the Δ connection.

In order to suppress 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 it does so, since the electric current for obtaining the same output torque will increase, the electric current which flows into the electric motor 7 and the inverter 30 will increase, and efficiency will fall.

Therefore, it is conceivable to switch the connection state according to the rotation speed. For example, when high-speed operation is required, a Δ connection state is set. In this way, the voltage required for driving can be reduced to 1 / √3 (compared to the Y connection). For this reason, it is not necessary to reduce the number of windings, and it is not necessary to use the flux-weakening control.

On the other hand, at low speed rotation, the current value can be reduced to 1 / √3 compared to the Δ connection by setting the Y connection state. Furthermore, 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 increased.

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

The control power generation circuit 80 receives and reduces the voltage between both electrodes of the capacitor 20, that is, the bus voltage V20, generates the control power V100 and the switching power supply V60, supplies the control power V100 to the control device 100, and performs switching. The power supply V60 is supplied to the connection switching device 60. For example, the voltage value of the control power supply V100 is 5V, and the voltage value of the switching power supply V60 is 12V. The switching power supply V60 supplies the current flowing through the exciting coils 611, 621, and 631 of the switching devices 61, 62, and 63.

The bus current detection means 85 detects the bus current, that is, the input current Idc of the inverter 30. The bus current detection means 85 includes a shunt resistor inserted into 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 converter (not shown) in the control device 100 and used for processing inside the control device 100.

The failure indicator 87 displays a failure of the connection switching device 60 according to the display control signal Sfc from the control device 100.

The control device 100 controls the switching of the connection state by the connection switching device 60 and the operation of the inverter 30 as described above. In order to control the inverter 30, the control device 100 generates PWM signals Sm1 to Sm6 and supplies them to the inverter 30.

The inverter 30 includes the drive circuit 350 in addition to the inverter main circuit 310 as described above. The drive circuit 350 generates the drive signals Sr1 to Sr6 based on the PWM signal, and the drive signals Sr1 to Sr6. The switching elements 311 to 316 are controlled to be turned on and off, so that a three-phase AC voltage having a variable frequency and a variable voltage is applied to the motor 7.

Whereas the PWM signals Sm1 to Sm6 are of a signal level magnitude (0 to 5V) of the logic circuit, the drive signals Sr1 to Sr6 are voltage levels necessary for controlling the switching elements 311 to 316, for example, It is a signal having a magnitude of + 15V to −15V. The PWM signals Sm1 to Sm6 have the ground potential of the control device 100 as a reference potential, whereas the drive signals Sr1 to Sr6 have potentials at the negative terminals (emitter terminals) of the corresponding switching elements, respectively. Is a reference potential.

The control apparatus 100 has the operation control part 102, the inverter control part 110, and the failure detection part 130, as shown in FIG.

The operation control unit 102 receives information Temp indicating a room temperature (temperature of the air-conditioning target space) detected by a temperature sensor (not shown), receives an instruction Ctr from an operation unit (not shown), for example, a remote controller, and operates each part of the air conditioner. To control. The instruction from the operation unit includes information indicating the set temperature, operation mode selection, operation start and end instructions, and the like.

The operation control unit 102 determines, for example, whether the stator winding of the electric motor 7 is Y-connected or Δ-connected and the target rotational speed, and based on the determination, the switching signal Sc and the frequency command value ω ^*. Is output. For example, if the difference between the room temperature and the set temperature is large, decide to use Δ connection, set the target rotational speed to a relatively high value, and after starting, a frequency command that gradually increases to the frequency corresponding to the target rotational speed The value ω ^* is output.

When the frequency corresponding to the target rotational speed is reached, the state is maintained until the room temperature approaches the set temperature. When the room temperature approaches the set temperature, the motor is stopped once and switched to the Y connection, and the target rotation is relatively low. The frequency command value ω ^* that gradually increases to the frequency corresponding to the number is output. When the frequency corresponding to the target rotational speed is reached, control for maintaining the room temperature close to the set temperature is performed thereafter. This control includes frequency adjustment, motor stop, restart, and the like.

The operation control unit 102 also performs a process of immediately stopping the inverter 30 when a failure of the connection switching device 60 is detected by the failure detection unit 130, as will be described later. The process of stopping the inverter 30 is performed by giving a signal (stop signal) St for stopping the inverter 30 to the inverter control unit 110.

The inverter control unit 110 includes a current restoration unit 111, a three-phase two-phase conversion unit 112, an excitation current command control unit 113, a voltage command calculation unit 114, an electrical angle phase calculation unit 115, a two-phase three-phase conversion unit 116, and PWM generation. Part 117.

The current restoration unit 111 restores the phase currents i _u , i _v , i _w flowing through the electric motor 7 based on the current value Idc detected by the bus current detection means 85. The phase current of the electric motor 7 here is a current that flows into the electric motor via the output lines 331, 332, and 333 of the inverter 30, and is also referred to as an inverter output current. The current restoration unit 111 samples the DC current Idc detected by the bus current detection unit 85 at a timing determined based on the PWM signal from the PWM generation unit 117, so that the phase currents i _u , i _v , i _w To restore.
The process of restoring the phase current in this way is an aspect of detecting the phase current.

The three-phase / two-phase conversion unit 112 uses the current values i _u , i _v , i _w restored by the current restoration unit 111 as the excitation current using the electrical angle phase θ generated by the electrical angle phase calculation unit 115 described later. It is converted into a dq-axis current value represented by a component (d-axis current) id and a torque current component (q-axis current) _iq .

Exciting current command control unit 113, based on the torque current component i _q, the most efficiency is improved optimum excitation current command value for driving the electric motor 7 (d-axis current command value) is obtained i _d ^*.
Although seeking exciting current command value i _d ^* based on the torque current component i _q in FIG. 7, the exciting current component i _d, or the exciting current command value i _d and the frequency command value omega ^* based on The same effect can be obtained even if ^* is obtained.

Based on the torque current component i _q (or the excitation current component _id or the frequency command value ω ^* ), the excitation current command control unit 113 outputs a torque that is greater than or equal to a predetermined value (or maximum), that is, the current value is less than or equal to a predetermined value. An excitation current command value i _d ^* is output such that the current phase angle β _m (not shown) is (or minimum).

The voltage command calculation unit 114 includes an excitation current component (d-axis current) _id and a torque current component (q-axis current) i _q obtained from the three-phase to two-phase conversion unit 112, a frequency command value ω ^*, and an excitation current. Based on the excitation current command value i _d ^* obtained from the command control unit 113, voltage command values V _d ^* and V _q ^* are output.

FIG. 8 is a diagram illustrating a configuration example of the voltage command calculation unit 114 of FIG. 8 includes a frequency estimation unit 1141, subtraction units 1142, 1144, and 1146, and control units 1143, 1145, and 1147.

The frequency estimator 1141 determines the excitation current component i _d and the torque current component i _q , the excitation voltage command value (d-axis voltage command value) V _d ^*, and the torque voltage command value (q-axis voltage command value) V _q ^* . Based on this, the frequency of the electric motor 7 is estimated, and the frequency estimated value ω _est is generated.

The subtraction unit 1142 obtains a difference (ω ^* −ω _est ) between the frequency command value ω ^* and the frequency estimation value ω _est generated by the frequency estimation unit 1141.
Based on the difference (ω ^* −ω _est ) obtained by the subtractor 1142, the control unit 1143 performs torque such that the frequency estimated value ω _est matches the frequency command value ω ^* by proportional integral (PI) control, for example. The current command value (q-axis current command value) i _q ^* is output.

Subtraction unit 1144 obtains the excitation current command value _i ^{d *} and the difference between the exciting current component ^{_{i d (i d * -i d}} ).
Control unit 1145, based on the determined at the subtraction unit 1144 difference ^_(i d * -i _d), for example, a proportional integral (PI) control, the exciting current component _{i d} is equal to the exciting current command value _i ^{d *} Such an excitation voltage command value V _d ^* is output.

The subtraction unit 1146 obtains a difference (i _q ^* −i _q ) between the torque current command value i _q ^* and the torque current component i _q .
Based on the difference (i _q ^* −i _q ) obtained by the subtraction unit 1146, the control unit 1147 matches the torque current component i _q with the torque current command value i _q ^* , for example, by proportional integration (PI) control. The q-axis voltage command value V _q ^* is output.

The electrical angle phase calculation unit 115 integrates the frequency estimation value ω _est generated by the voltage command calculation unit 114 to obtain the electrical angle phase θ.

The two-phase / three-phase converter 116 converts the excitation voltage command value V _d ^* and the torque voltage command value V _q ^* (the voltage command value of the two-phase coordinate system) obtained by the voltage command calculator 114 into the electrical angle phase calculator 115. _Is converted into an output voltage command value (three-phase voltage command value) V _u ^* , V _v ^* , V _w ^* of the three-phase coordinate system using the electrical angle phase θ obtained by the above-mentioned output.

The PWM generator 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 converter 116. The PWM signals Sm1 to Sm6 are used to turn on / off the switching elements 311 to 316 of each arm of the inverter 30 so that the output voltage of the inverter 30 matches the three-phase voltage command values V _u ^* , V _v ^* , and V _w ^*. Is a signal for controlling

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

The stop signal St that is a signal for stopping the inverter 30 is given to, for example, the PWM generation unit 117. Upon receiving the stop signal St, the PWM generation unit 117 immediately stops outputting the PWM signals Sm1 to Sm6.

The failure detection unit 130 includes inverter output currents i _u , i _v , i _w restored by the current restoration unit 111, excitation current component _id and torque current component i _q output from the three-phase two-phase conversion unit 112, and A failure of the connection switching device 60 is detected based on the switching signal Sc. Hereinafter, the connection switching device 60 may be simply referred to as the switching device 60.

Hereinafter, a failure to be detected by the failure detection unit 130 will be described.
FIGS. 9A and 9B show examples of different failures.

In the example shown in FIG. 9A, the switches 62 and 63 are in the Δ connection switching state, while the switch 61 is in the Y connection switching state.
This occurs when the switch 61 is in the Δ connection switching state due to a failure even though the switching signal Sc is in the Y connection designated state (Low), or when the switching signal Sc is Δ This is a case where the switchers 62 and 63 are in the Y connection switching state due to a failure although the connection is in the designated state (High).
In that case, the windings 71, 72, 73 are connected as shown in FIG.

In the example shown in FIG. 9B, the switches 62 and 63 are in the Δ connection switching state, while the switch 61 is in the Y connection switching state.
This occurs when the switch 61 is in the Y connection switching state due to a failure even though the switching signal Sc is in a state (High) for designating Δ connection, or when the switch signal Sc is This is a case where the switchers 62 and 63 are in the Δ connection switching state due to a failure although the Y connection is in the designated state (Low).
In that case, the windings 71, 72, 73 are connected as shown in FIG.

Hereinafter, the states shown in FIGS. 9A and 10A are expressed as “U phase only Δ”, and the states shown in FIGS. 9B and 10B are expressed as “U phase”. Only Y ”state is expressed. As the failure state, in addition to the states shown in FIGS. 9A and 9B and FIGS. 10A and 10B, the “V phase only Δ” state, the “W phase only Δ” state, There are six states in total, that is, a state of “V phase only Y” and a “W phase only Y” state.

The above “state” is not only the connection state of the windings but also the state of the switching device 60. Therefore, for example, the expression “U phase only Δ” is used for both the connection state of the windings and the switching state of the switching device 60.

Becomes to any of such six states, the inverter output current becomes unbalanced, the exciting current component i _d and a torque current component i _q obtained by converting the inverter output current is many harmonic components Will be included.

For example, in the state of “U phase only Δ” shown in FIG. 9A and FIG. 10A, the inverter output current, the excitation current component _id and the torque current component i _q corresponding thereto are shown in FIG. As shown in (a) and (b).
In the state of “U phase only Y” shown in FIG. 9B and FIG. 10B, the inverter output currents i _u , i _v , i _w and the corresponding excitation current components i _d and torque The current component i _q is as shown in FIGS. 12 (a) and 12 (b).

11 (a) and 11 (b) and FIGS. 12 (a) and 12 (b), the inverter output current is unbalanced, and the excitation current component _id and the torque current component _iq have many harmonics. It can be seen that the wave component is included. This harmonic component is mainly a second harmonic component. The harmonic component referred to here is a component having a frequency that is an integral multiple of the fundamental wave of the inverter output currents i _u , i _v , i _w before conversion in the three-phase / two-phase converter 112.

The failure detection unit 130 detects a failure based on the harmonic component included in the excitation current component _id and the torque current component _iq , and determines the failure mode based on the relationship between the magnitudes of the inverter output currents. To identify.

The failure is detected by giving a switching signal Sc to the switching device 60 to specify the switching state, operating the inverter 30 to apply a voltage from the inverter 30 to the electric motor 7, and based on the value of the current flowing through the electric motor at that time. Do it.

Failure detection is typically performed when the switching device 60 is switched. For example, the failure is detected based on the current of each phase immediately after switching the value or state of the switching signal Sc from the state where the motor 7 is in either the Y-connection state or the Δ-connection state and no abnormality is detected. Done. However, the failure detection may be performed also when the operation of the electric motor driving device is started.

The failure detection unit 130 includes a harmonic detection unit 131, an unbalance detection unit 132, and a failure determination unit 133, for example, as shown in FIG.

Harmonics detection unit 131 detects a failure of the switching device 60 from the harmonic component of the exciting current component i _d and a torque current component i _q obtained by conversion in the three-to-two phase converter 112.
Harmonics detection unit 131 extracts a harmonic component from each of the exciting current component i _d and a torque current component i _q, for at least one of the exciting current component i _d and a torque current component i _q, the amount of harmonic components It is determined whether or not it is larger than that in the normal state, and a signal Sdf indicating the determination result is sent to the failure determination unit 133.

Extraction of the harmonic component can be performed by, for example, high-pass filtering, band-pass filtering, or FFT (Fast Fourier Transform).
“Normal time” means a time when there is no failure in the switching device 60.
Whether or not it is larger than normal is, for example, whether or not the amount of harmonic components in normal is larger than the upper limit of a possible value range (variation range) or a threshold set to a value larger than that. judge. For example, the threshold value is set to twice the above upper limit value.

The harmonic detection unit 131 outputs a signal Sdf indicating the result of failure detection. For example, the signal Sdf, for at least one of the exciting current component i _d and a torque current component i _q, when the amount of the harmonic component is greater than that in the normal, the first value, for example High next, else , The second value, for example, Low.

The unbalance detection unit 132 specifies the failure mode based on the inverter output currents i _u , i _v , i _w and the switching signal Sc, and outputs a signal Sfa indicating the specified failure mode.
For example, the unbalance detection unit 132 specifies the switching state of the switching device 60 based on the relationship between the magnitudes Imu, Imv, and Imw of the inverter output currents i _u , i _v , and i _w , The failure mode of the switching device 60 is specified based on the switching signal Sc.

As the magnitudes Imu, Imv, Imw of the inverter output currents i _u , i _v , i _w , for example, the maximum value for each predetermined period, the effective value for each predetermined period, or for each predetermined period An average value of absolute values of can be used.

FIGS. 14A to 14C show paths of currents flowing from the external terminals 71c, 72c, and 73c when the winding is in the “U phase only Δ” connection state shown in FIG.
That is, FIG. 14 (a) shows the path of the current _{i u} flowing from the external terminal 71c of the U-phase, FIG. 14 (b) shows the path of the current _{i v} flowing from the V-phase external terminal 72c, FIG. 14 (c) shows the path of the current _{i w} flowing from the W-phase external terminal 73c.
14A to 14C, Z represents the impedance of the winding of each phase.

14A to 14C, the impedance Zu viewed from the U-phase external terminal 71c, the impedance Zv viewed from the V-phase external terminal 72c, and the impedance Zw viewed from the W-phase external terminal 73c. Is
Zw>Zu> Zv
It can be seen that there is a relationship.

In this case, between the magnitudes Imu, Imv, Imw of the inverter output current (if the applied voltage is the same),
Imv>Imu> Imw
There is a relationship.

Similarly, in the connection state of “V phase only Δ”, there is a relationship of Imw> Imv> Imu, and in the connection state of “W phase only Δ”, there is a relationship of Imu> Imw> Imv.

FIGS. 15A to 15C show paths of currents flowing from the external terminals 71c, 72c, and 73c when the winding is in the “U phase only Y” connection state shown in FIG. 10B.
That is, FIG. 15 (a) shows the path of the current _{i u} flowing from the external terminal 71c of the U-phase, FIG. 15 (b) shows the path of the current _{i v} flowing from the V-phase external terminal 72c, FIG. 15 (c) shows the path of the current _{i w} flowing from the W-phase external terminal 73c.
15A to 15C, Z represents the impedance of the winding of each phase.

15A to 15C, the impedance Zu viewed from the U-phase external terminal 71c, the impedance Zv viewed from the V-phase external terminal 72c, and the impedance Zw viewed from the W-phase external terminal 73c. Is
Zu = Zv> Zw
It can be seen that there is a relationship.

In this case, the magnitude of the inverter output current is between Imu, Imv, and Imw (if the applied voltage is the same)
Imw> Imu = Imv
There is a relationship.

Similarly, in the connection state of “V phase only Y”, there is a relationship of Imu> Imv = Imw, and in the connection state of “W phase only Y”, there is a relationship of Imv> Imu = Imw.

The unbalance detection unit 132 specifies the connection state of the windings using the relationship between the magnitudes of the inverter output currents i _u , i _v , i _w when the switching device 60 fails, The switching state of the switching device 60 is specified by

First, the unbalance detection unit 132 obtains the magnitudes Imu, Imv, Imw of the inverter output currents i _u , i _v , i _w restored by the current restoration unit 111.
Next, the unbalance detection unit 132 determines whether or not the obtained magnitudes Imu, Imv, and Imw of the inverter output current satisfy any of the following conditions CP1 to CP6.
Condition CP1: Imv>Imu> Imw
Condition CP2: Imw>Imv> Imu
Condition CP3: Imu>Imw> Imv
Condition CP4: Imw> Imu = Imv
Condition CP5: Imu> Imv = Imw
Condition CP6: Imv> Imu = Imw

However, in the comparison of the magnitudes of the two currents, the difference in the magnitudes of the currents is considered to be a threshold value (first value) in consideration of variations in winding impedance, inverter output current errors, current measurement errors, calculation errors, and the like. If the difference is equal to or greater than the threshold, it is determined that there is a magnitude relationship. That is, when the magnitudes of the two currents are represented by Ia and Ib,
| Ia-Ib | <It1
(However, It1 is a threshold value)
Then treat Ia as equal to Ib,
If Ib ≦ Ia−It1, Ib is treated as being smaller than Ia,
If Ib ≧ Ia + It1, Ib is treated as greater than Ia.

Based on which of the conditions CP1 to CP6 is satisfied, the unbalance detection unit 132 determines the switching state as follows.
When the condition CP1 is satisfied, the switching device 60 determines that the “U phase only Δ” is in the switching state. This state is referred to as a first switching state CS1.
Similarly, when the condition CP2 is satisfied, it is determined that the connecting device is in the “V phase only Δ” switching state. This state is referred to as a second switching state CS2.
When the condition CP3 is satisfied, it is determined that the connection device is in the “W phase only Δ” switching state. This state is referred to as a third switching state CS3.

When the condition CP4 is satisfied, it is determined that the connecting device is in the “U phase only Y” switching state. This state is referred to as a fourth switching state CS4.
When the condition CP5 is satisfied, it is determined that the connection device is in the “V phase only Y” switching state. This state is referred to as a fifth switching state CS5.
When the condition CP6 is satisfied, it is determined that the connecting device is in the “W phase only Y” switching state. This state is referred to as a sixth switching state CS6.

The determination about the switching state based on the magnitude of the current can be summarized as follows.
That is, if the current of one phase is smaller than the current of one of the other two phases and larger than the current of the other phase, the unbalance detection unit 132 determines that the switch of the one phase is It is in the Δ connection switching state, and the other two phase switch is determined to be in the Y connection switching state, and the current of one phase is smaller than the current of one of the other two phases. If the current of the other phase is equal, the unbalance detection unit 132 indicates that the one-phase switch is in the Y-connection switching state and the other two-phase switching devices are in the Δ-connection switching state. judge.

As described above, when an amount is greater than another amount, the difference is greater than or equal to a threshold, and when an amount is equal to another amount, the difference from the other amount is less than the threshold. Means that.
Therefore, it can be paraphrased as follows.

If the current of one phase is at least a first threshold (It1) smaller than the current of one of the other two phases and at least the first threshold (It1) greater than the current of the other phase The unbalance detection unit 132 determines that the one phase switch is in the Δ connection switching state and the other two phase switch is in the Y connection switching state, and the current of one phase is The current of one phase of the other two phases is smaller by at least the first threshold (It1), and the difference between the current of the one phase and the current of the other phase is smaller than the first threshold (It1). If not, the unbalance detection unit 132 determines that the one-phase switch is in the Y-connection switching state, and the other two-phase switching devices are in the Δ-connection switching state.
The switching state of the switching device 60 is specified as described above.

When any one of the above conditions CP1 to CP6 is satisfied, the unbalance detection unit 132 determines the value of the switching signal Sc and which of the above conditions CP1 to CP6 is satisfied, that is, The following determination is made based on the identified switching state.

When the switching signal Sc is High and the condition CP1 is satisfied (when “U phase only Δ”), the unbalance detection unit 132 causes the V phase switch 62 and the W phase switch 63 to fail. It is determined that This is because the switching devices 62 and 63 are in the Y connection switching state even though the switching signal Sc is High and the Δ connection is designated thereby. Such a failure mode is referred to as a first mode Ma1.

When the switching signal Sc is High and the condition CP2 is satisfied (when “V-phase only Δ”), the unbalance detection unit 132 causes the U-phase switch 61 and the W-phase switch 63 to fail. It is determined that This is because the switching devices 61 and 63 are in the Y connection switching state even though the switching signal Sc is High and the Δ connection is designated by this. Such a failure mode is referred to as a second mode Ma2.

When the switching signal Sc is High and the condition CP3 is satisfied (when “only W phase is Δ”), the unbalance detection unit 132 is caused by the failure of the U-phase switch 61 and the V-phase switch 62. It is determined that This is because the switching devices 61 and 62 are in the switching state for the Y connection even though the switching signal Sc is High and the Δ connection is thereby designated. Such a failure mode is referred to as a third mode Ma3.

When the switching signal Sc is High and the condition CP4 is satisfied (“U phase only Y”), the unbalance detection unit 132 determines that the U phase switch 61 has failed. This is because the switch 61 is in the switching state for the Y connection even though the switching signal Sc is High and the Δ connection is designated by this. Such a failure mode is referred to as a fourth mode Ma4.

When the switching signal Sc is High and the condition CP5 is satisfied (“V phase only Y”), the unbalance detection unit 132 determines that the V phase switch 62 has failed. This is because the switching device 62 is in the Y connection switching state even though the switching signal Sc is High and the Δ connection is designated thereby. Such a failure mode is referred to as a fifth mode Ma5.

When the switching signal Sc is High and the condition CP6 is satisfied (when “only W phase is Y”), the unbalance detection unit 132 determines that the W phase switching unit 63 has failed. This is because the switching device 63 is in the Y connection switching state even though the switching signal Sc is High and the Δ connection is designated thereby. Such a failure mode is referred to as a sixth mode Ma6.

When the switching signal Sc is Low and the condition CP1 is satisfied (when only the U phase is Δ), the unbalance detecting unit 132 determines that the U phase switching device 61 has failed. This is because the switching device 61 is in the Δ connection switching state even though the switching signal Sc is Low and the Y connection is thereby designated. Such a failure mode is referred to as a seventh mode Ma7.

When the switching signal Sc is Low and the condition CP2 is satisfied (when only the V-phase is Δ), the unbalance detection unit 132 determines that the V-phase switch 62 has failed. This is because the switching device 62 is in the Δ connection switching state even though the switching signal Sc is Low and the Y connection is designated thereby. Such a failure mode is referred to as an eighth mode Ma8.

When the switching signal Sc is Low and the condition CP3 is satisfied (when “only W phase is Δ”), the unbalance detection unit 132 determines that the W phase switching unit 63 has failed. This is because the switching device 63 is in the Δ connection switching state even though the switching signal Sc is Low and the Y connection is thereby designated. Such a failure mode is referred to as a ninth mode Ma9.

When the switching signal Sc is Low and the condition CP4 is satisfied (when “U phase only is Y”), the unbalance detection unit 132 detects that the V phase switch 62 and the W phase switch 63 fail. It is determined that This is because the switching devices 62 and 63 are in the Δ connection switching state even though the switching signal Sc is Low and the Y connection is thereby designated. Such a failure mode is referred to as a tenth mode Ma10.

When the switching signal Sc is Low and the condition CP5 is satisfied (when only “V phase is Y”), the unbalance detection unit 132 detects that the U phase switch 61 and the W phase switch 63 fail. It is determined that This is because the switching devices 61 and 63 are in the Δ connection switching state even though the switching signal Sc is Low and the Y connection is designated thereby. Such a failure mode is referred to as an eleventh mode Ma11.

When the switching signal Sc is low and the condition CP6 is satisfied (when “only W phase is Y”), the unbalance detection unit 132 detects that the U-phase switch 61 and the V-phase switch 62 have failed. It is determined that This is because the switching devices 61 and 62 are in the Δ connection switching state although the switching signal Sc is Low and the Y connection is designated by this. Such a failure mode is referred to as a twelfth mode Ma12.

Based on the switching state and the switching signal Sc described above, the process of identifying the failed switcher can be summarized as follows.
That is, when the Y connection is specified by the switching signal Sc, the unbalance detection unit 132 determines that the switch in the Δ connection switching state is out of order, and the Δ connection is specified by the switching signal Sc. If the switch is in the Y connection switching state, it is determined that the switch has failed.

The above determination is shown in FIG.
As can be seen from the above description and FIG. 16, there are twelve failure modes Ma1-Ma12, and the signal Sfa indicates which of the twelve modes Ma1-Ma12 the failure is.
The unbalance detection unit 132 sends a signal Sfa indicating the determination result to the failure determination unit 133.

The failure determination unit 133 outputs a signal indicating the result of the failure determination based on the signal Sfa and the signal Sdf and a signal indicating the failed switch. The failure determination unit 133 may output a signal indicating the connection designated by the switching signal Sc when a failure is detected, together with a signal indicating the failed switch.

For example, if the signal Sdf is High and the signal Sfa indicates one of the failure modes Ma1 to Ma12, the failure determination unit 133 determines that the switching device 60 has a failure.
When it is determined that there is a failure, the failure determination unit 133 sends a failure detection signal Sdg to the operation control unit 102.

When the failure detection signal Sdg is sent, the operation control unit 102 outputs the inverter stop signal St. In response to the stop signal St, the PWM generator 117 stops outputting the PWM signals Sm1 to Sm6. As a result, the inverter 30 stops outputting the AC voltage.

If the signal Sdf is High, the failure determination unit 133 generates a display control signal Sfc indicating the switch that has failed based on the signal Sfa, and supplies the display control signal Sfc to the failure indicator 87.
For example, when the signal Sfa indicates the failure mode Ma1, a signal indicating that the V-phase switch 62 and the W-phase switch 63 are broken is generated as the display control signal Sfc.
The failure determination unit 133 may also output a signal indicating the connection designated by the switching signal Sc when a failure is detected.

The failure indicator 87 displays the failed switch according to the display control signal Sfc indicating the failed switch.
In repairing, it is possible to identify the switch that has failed by looking at the display of the failure indicator 87, and therefore repair can be performed promptly.

When a signal indicating the connection designated by the switching signal Sc when a failure is detected is also output, the failure indicator 87 displays the switching state when the failure is detected. If the switching state when a failure is detected is also displayed, the failure can be repaired more quickly.

Even if the signal Sfa does not indicate any of the modes Ma1 to Ma12, if the signal Sdf is High, the failure detection signal Sdg may be High. In that case, although the failed switching device cannot be specified, the inverter can be stopped by detecting the failure, so that the motor can be prevented from being damaged and demagnetized.

As described above, according to the first embodiment, it is possible to quickly detect when the switching device 60 breaks down, stop the inverter, and prevent damage to the motor and demagnetization.
Further, if the failure mode or the failed switching device is displayed on the failure indicator, the failure switching device can be easily identified and repaired quickly.

Embodiment 2. FIG.
In the first embodiment, the inverter output currents i _u , i _v , i _w are restored from the DC current Idc on the input side of the inverter 30, but current detection is performed on the output lines 331, 332, 333 of the inverter 30. An element may be provided, and the inverter output currents i _u , i _v , i _w may be detected by the current detection element. In this case, the current detected by the current detection element is converted into a current restoring unit. It may be used instead of the current restored in 111.

FIG. 17 is a schematic wiring diagram showing the electric motor drive device 2 b of the second embodiment together with the electric motor 7.
The motor drive device 2b shown in FIG. 17 is generally the same as the motor drive device 2 shown in FIG. However, the bus current detection means 85 is not provided, but current detection elements 91, 92, and 93 are provided instead, and a control device 100 b is provided instead of the control device 100.

The current detection elements 91, 92, 93 are provided so as to detect the inverter output current, that is, the current flowing through the inverter output lines 331, 332, 333. Signals obtained by detection by the current detection elements 91, 92, and 93 are converted into digital signals by an A / D converter (not shown) in the control device 100b and used for processing inside the control device 100b.

FIG. 18 shows the control device 100b of FIG.
The control device 100b of FIG. 18 is generally the same as the control device 100 of FIG. 7, but an inverter control unit 110b is provided instead of the inverter control unit 110.
The inverter control unit 110b is generally the same as the inverter control unit 110, but the current restoration unit 111 is not provided, and the current values detected by the current detection elements 91, 92, 93 are directly three-phase to two-phase conversion unit 112. And the failure detection unit 130.

The three-phase / two-phase conversion unit 112 and the failure detection unit 130 are current values detected by the current detection elements 91, 92, 93 instead of the current values i _u , i _v , i _w output from the current restoration unit 111. Using i _u , i _v , and i _w , processing similar to that described in the first embodiment is performed.

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

Embodiment 3 FIG.
In the first and second embodiments, the failure of the switching device 60 is detected based on the currents i _u , i _v and i _w flowing from the inverter 30 to the electric motor 7. Instead, the current flowing through the winding of the electric motor 7 may be detected, and the failure of the switching device 60 may be detected based on the detection result.

Here, “detection of the current flowing through the winding of the electric motor 7” means that the current flowing through the winding of the electric motor 7 is detected both in the case of Y connection and Δ connection. In the case of Y connection, the currents i _u , i _v and i _w flowing from the inverter 30 to the motor 7 are equal to the current flowing in the winding of the motor 7, but in the case of Δ connection, the winding of the motor 7 Is not equal to the current flowing through

FIG. 19 is a schematic wiring diagram showing the electric motor drive device 2 c of the third embodiment together with the electric motor 7.
The electric motor drive device 2c shown in FIG. 19 is generally the same as the electric motor drive device 2 shown in FIG. However, the bus current detection means 85 is not provided, but current detection elements 96, 97, and 98 are provided instead, and a control device 100 c is provided instead of the control device 100.

The current detection elements 96, 97, 98 are provided so as to detect the winding current of the motor, that is, the current flowing through the U-phase, V-phase, and W- phase windings 71, 72, 73 of the motor. That is, in the third embodiment, the current detection elements 96, 97, and 98 are provided at positions where the current flowing through the winding can be detected regardless of whether the connection state is Y connection or Δ connection.

Signals obtained by detection by the current detection elements 96, 97, and 98 are converted into digital signals by an A / D converter (not shown) in the control device 100c and used for processing inside the control device 100c.

FIG. 20 shows the stator windings 71, 72, 73 and the connection switching device 60 of the electric motor 7 and the current detection elements 96, 97, 98 in more detail.

In the configuration shown in FIGS. 19 and 20, the first current detection element 96 is connected to the external terminal 71 d to which the end 71 b of the U-phase winding 71 is connected and the common contact 61 c of the switch 61. The second current detection element 97 is connected to the external terminal 72d connected to the end 72b of the V-phase winding 72 and the common contact 62c of the switch 62. The third current detection element 98 is provided to detect the current flowing through 62e, and the third current detection element 98 connects the external terminal 73d to which the end 73b of the W-phase winding 73 is connected and the common contact 63c of the switch 63. It is provided to detect the current flowing through the line 63e.

FIG. 21 shows the control device 100c of FIG.
The control device 100c of FIG. 21 is generally the same as the control device 100 of FIG. 7, but an inverter control unit 110c is provided instead of the inverter control unit 110.

The inverter control unit 110c is generally the same as the inverter control unit 110, but a three-phase / two-phase conversion unit 112c and a failure detection unit 130c are provided instead of the three-phase / two-phase conversion unit 112 and the failure detection unit 130 of FIG. Further, the current restoring unit 111 is not provided.
The winding currents i _cu , i _cv , and i _cw detected by the current detection elements 96, 97, and 98 are input to the three-phase / two-phase conversion unit 112 c and the failure detection unit 130 c.

The three-phase to two-phase conversion unit 112b uses the winding currents i _cu , i _cv , and i _cw as the excitation current component i _d and the torque current component i _q using the electrical angle phase θ generated by the electrical angle phase calculation unit 115. Convert to

19 is based on the winding currents i _cu , i _cv , i _cw , the excitation current component _id and torque current component i _q output from the three-phase / two-phase converter 112 _c, and the switching signal Sc. Thus, the failure of the switching device 60 is detected. The failure to be detected in the third embodiment and the timing at which the failure is detected are the same as those in the first embodiment. In the following, with respect to the failure detection unit 130c, a description will be mainly given of portions different from the failure detection unit 130 of the first embodiment.

19 includes a harmonic detection unit 131, an unbalance detection unit 132c, and a failure determination unit 133c, for example, as shown in FIG.

Harmonics detection unit 131, like the harmonics detection unit 131 of the first embodiment, to extract the harmonic component from each of the exciting current component i _d and a torque current component i _q, the exciting current component i _d and a torque current component for at least one of i _q, the amount of the harmonic component is determined whether more than that in the normal, sends a signal Sdf indicating the determination result to the malfunction determining unit 133.

Based on the winding currents i _cu , i _cv , i _cw, and the switching signal Sc, the unbalance detection unit 132 c specifies the failure mode and outputs a signal Sfb indicating the specified failure mode.
Unbalance detector 132c is, for example, allow the winding current _{i cu,} i _cv, the magnitude of the sum of the instantaneous values of each two of the _{i cw} (winding current _{i cu,} i _cv, duplicates from _{i cw} When three sets of two selected in the above are formed, the magnitude of the sum of instantaneous values of two winding currents constituting each of the three sets) and the magnitude of the winding current The switching state of the switching device 60 is specified based on the switching state, and the failure mode of the switching device 60 is specified based on the specified switching state and the switching signal Sc.

FIGS. 23 (a) and 23 (b) are diagrams similar to FIGS. 10 (a) and 10 (b), but the winding currents are indicated by symbols i _cu , i _cv , and i _cw .

In the connection state of “U phase only Δ” shown in FIG. 23A, the current i _cv and the current i _cw are in a reverse phase relationship as shown in FIG. The magnitude Isvw becomes zero.
As the magnitude of the sum of the instantaneous values, for example, the maximum value of the sum (instantaneous value) for each predetermined period, the effective value for each predetermined period, or the average value of the absolute values for each predetermined period Can be used.

Similarly to the case shown in FIG. 24A, in the connection state of “Δ for V phase only”, the sum Isuw of the instantaneous value of the current i _{cu and} the instantaneous value of the current i _cw becomes zero, and “W In the connection state of “phase only Δ”, the magnitude Isuv of the sum of the instantaneous value of the current i _{cu and} the instantaneous value of the current i _cv becomes zero.

In the connection state of “U phase only Y” shown in FIG. 23B, as shown in FIG. 24B, the V phase winding current i _cv and the W phase winding current i _cw are normal. is similar, size Imcu winding current _{i cu} of U-phase is zero.
As the magnitude of the winding current, for example, a maximum value for each predetermined period, an effective value for each predetermined period, or an average value of absolute values for each predetermined period can be used.

Similarly to the case shown in FIG. 24B, in the connection state of “V phase only Y”, the magnitude of the V-phase winding current Imcv becomes zero, and in the connection state of “W phase only Y”, the W phase The winding current magnitude Imcw becomes zero.

Unbalance detector 132c is in failure of the switching device 60 described above, the winding current _{i cu, i cv, i cw} size Imcu, Imcv, Imcw, and the winding current _{i cu,} i _cv, the _{i cw} Based on the magnitudes Imcu, Imcv, and Imcw of the sum of two instantaneous values of each of them, the connection state of the winding is specified, and thereby the switching state of the switching device 60 is specified.

Unbalance detector 132c firstly, the current detected by the detection elements 96, 97, 98 the winding current _{i cu, i cv, i cw} size Imcu, Imcv, Imcw, and the winding current _{i cu, i cv,} the size of the sum of instantaneous values of each two of the i _cw isvw, Isuw, seeking Isuv.
Next, the unbalance detection unit 132c determines that the obtained winding current magnitudes Imcu, Imcv, Immcw, and the sum magnitudes of two instantaneous values of the winding currents, Isvw, Isuw, Isuv, are as follows: It is determined whether or not any of the conditions CQ1 to CQ6 is satisfied.
Condition CQ1: Isvw = 0
Condition CQ2: Isuw = 0
Condition CQ3: Isuv = 0
Condition CQ4: Imcu = 0
Condition CQ5: Imcv = 0
Condition CQ6: Imcw = 0

However, in determining whether the magnitude of the sum of two instantaneous values of the winding currents i _cu , i _cv , and i _cw is equal to zero, taking measurement error, calculation error, etc. into consideration, If the sum is smaller than a threshold (second threshold), it is considered to be zero.
Similarly, in determining whether or not the magnitudes of the winding currents i _cu , i _cv , and i _cw are equal to zero, taking the measurement error, calculation error, and the like into consideration, the magnitude is set to a threshold value (third If it is smaller than (threshold), it is considered to be zero.

Based on which of the conditions CQ1 to CQ6 is satisfied, the unbalance detection unit 132c makes the following determination regarding the switching state.
When the condition CQ1 is satisfied, the connecting device determines that the “U phase only Δ” is in the switching state. This state is referred to as a first switching state CS1.

Similarly, when the condition CQ2 is satisfied, the connection apparatus determines that the state is in the “V phase only Δ” switching state. This state is referred to as a second switching state CS2.
When the condition CQ3 is satisfied, the connecting device determines that the state is the “W phase only Δ” switching state. This state is referred to as a third switching state CS3.

When the condition CQ4 is satisfied, the connection apparatus determines that the “U phase only Y” switching state is set. This state is referred to as a fourth switching state CS4.
When the condition CQ5 is satisfied, the connection device determines that the switching state is “V phase only Y”. This state is referred to as a fifth switching state CS5.
When the condition CQ6 is satisfied, the wiring device determines that the state is in the “W phase only Y” switching state. This state is referred to as a sixth switching state CS6.

The judgment on the switching state based on the current magnitude and the sum of the instantaneous current values can be summarized as follows.

That is, if the magnitude of the sum of the instantaneous values of the currents of the other two phases other than one phase is equal to zero, the unbalance detection unit 132c indicates that the one-phase switch is in the Δ connection switching state. If it is determined that the other two phase switching devices are in the Y-connection switching state, and the current magnitude of one phase is equal to zero, the unbalance detection unit 132c determines that the one phase switching device is It is determined that it is in the Y connection switching state, and the other two-phase switches are in the Δ connection switching state.

As described above, an amount equal to zero means that the difference from zero is smaller than the threshold value. Therefore, it can be paraphrased as follows.

If the sum of the instantaneous values of the currents of the other two phases other than one phase is smaller than the threshold value (second threshold value), the unbalance detection unit 132c indicates that the one-phase switch is Δ-connected. If it is determined that the other two phase switching units are in the Y connection switching state and the current magnitude of one phase is smaller than the threshold value (third threshold value), the unbalance is detected. The unit 132c determines that the one-phase switch is in the Y-connection switching state and the other two-phase switching devices are in the Δ-connection switching state.
The switching state of the switching device 60 is specified as described above.

It should be noted that additional conditions may be set for each of the conditions CQ1 to CQ6 in order to prevent erroneous determination while the inverter output voltage immediately after startup is not sufficiently high.
For example, the condition that at least one of the winding currents is not zero may be an additional condition of the above conditions CQ1 to CQ3.
That is, it is determined that the condition CQ1 is satisfied when at least one of “Imcu ≠ 0”, “Imcv ≠ 0”, and “Imcw ≠ 0” is satisfied and “Isvw = 0” is satisfied,
It is determined that the condition CQ2 is satisfied when at least one of “Imcu ≠ 0”, “Imcv ≠ 0”, and “Imcw ≠ 0” is satisfied and “Isuw = 0” is satisfied,
It may be determined that the condition CQ3 is satisfied when at least one of “Imcu ≠ 0”, “Imcv ≠ 0”, and “Imcw ≠ 0” is satisfied and “Isuw = 0” is satisfied.

Further, the condition that at least one of the other winding currents is not zero may be an additional condition of the above conditions CQ4 to CQ6.
That is, when at least one of “Imcv ≠ 0” and “Imcw ≠ 0” is satisfied and “Imcu = 0” is satisfied, it is determined that the condition CQ4 is satisfied,
It is determined that the condition CQ5 is satisfied when at least one of “Imcu ≠ 0” and “Imcw ≠ 0” is satisfied and “Imcv = 0” is satisfied,
It may be determined that the condition CQ6 is satisfied when at least one of “Imcu ≠ 0” and “Imcv ≠ 0” is satisfied and “Imcw = 0” is satisfied.

Also in these cases, in the same manner as described above, in determining whether the magnitudes of the winding currents Imcu, Imcv, and Imcw are equal to zero, the magnitudes of the winding currents are taken into account in consideration of measurement errors, calculation errors, and the like. If it is smaller than the threshold (third threshold), it is regarded as zero.

When any one of the above conditions CQ1 to CQ6 is satisfied, the unbalance detection unit 132c determines whether the value of the switching signal Sc and any of the above conditions CQ1 to CQ6 is satisfied, that is, The following determination is made based on the identified switching state.

When the switching signal Sc is High and the condition CQ1 is satisfied (when “U-phase only Δ”), the unbalance detection unit 132c causes the V-phase switch 62 and the W-phase switch 63 to fail. It is determined that This is because the switching devices 62 and 63 are in the Y connection switching state even though the switching signal Sc is High and the Δ connection is designated thereby. Such a failure mode is referred to as a first mode Mb1.

When the switching signal Sc is High and the condition CQ2 is satisfied (when “V phase only Δ”), the unbalance detection unit 132c causes the U phase switch 61 and the W phase switch 63 to fail. It is determined that This is because the switching devices 61 and 63 are in the Y connection switching state even though the switching signal Sc is High and the Δ connection is designated by this. Such a failure mode is referred to as a second mode Mb2.

When the switching signal Sc is High and the condition CQ3 is satisfied (when “only W phase is Δ”), the unbalance detection unit 132c causes the U-phase switch 61 and the V-phase switch 62 to fail. It is determined that This is because the switching devices 61 and 62 are in the Y connection switching state even though the switching signal Sc is High and the Δ connection is designated thereby. Such a failure mode is referred to as a third mode Mb3.

When the switching signal Sc is High and the condition CQ4 is satisfied (“U phase only Y”), the unbalance detection unit 132c determines that the U phase switch 61 has failed. This is because the switch 61 is in the switching state for the Y connection even though the switching signal Sc is High and the Δ connection is designated by this. Such a failure mode is referred to as a fourth mode Mb4.

When the switching signal Sc is High and the condition CQ5 is satisfied (when “V phase only is Y”), the unbalance detection unit 132c determines that the V phase switch 62 has failed. This is because the switch 62 is in the switching state for the Y connection even though the switching signal Sc is High and the Δ connection is designated by this. Such a failure mode is referred to as a fifth mode Mb5.

When the switching signal Sc is High and the condition CQ6 is satisfied (when “only W phase is Y”), the unbalance detection unit 132c determines that the W phase switch 63 has failed. This is because the switch 63 is in the switching state for the Y connection even though the switching signal Sc is High and the Δ connection is designated by this. Such a failure mode is referred to as a sixth mode Mb6.

When the switching signal Sc is Low and the condition CQ1 is satisfied (when “U phase only Δ”), the unbalance detection unit 132c determines that the U phase switch 61 is out of order. This is because the switching device 61 is in the Δ connection switching state even though the switching signal Sc is Low and the Y connection is thereby designated. Such a failure mode is referred to as a seventh mode Mb7.

When the switching signal Sc is Low and the condition CQ2 is satisfied (when “only V phase is Δ”), the unbalance detecting unit 132c determines that the V phase switching unit 62 has failed. This is because the switching device 62 is in the Δ connection switching state even though the switching signal Sc is Low and the Y connection is designated thereby. Such a failure mode is referred to as an eighth mode Mb8.

When the switching signal Sc is Low and the condition CQ3 is satisfied (when “only W phase is Δ”), the unbalance detection unit 132c determines that the W phase switching unit 63 has failed. This is because the switching device 63 is in the Δ connection switching state even though the switching signal Sc is Low and the Y connection is thereby designated. Such a failure mode is referred to as a ninth mode Mb9.

When the switching signal Sc is Low and the condition CQ4 is satisfied (when “U phase only is Y”), the unbalance detection unit 132c causes the V phase switch 62 and the W phase switch 63 to fail. It is determined that This is because the switching devices 62 and 63 are in the Δ connection switching state even though the switching signal Sc is Low and the Y connection is thereby designated. Such a failure mode is referred to as a tenth mode Mb10.

When the switching signal Sc is Low and the condition CQ5 is satisfied (when “V-phase only Y”), the unbalance detection unit 132c is caused by the failure of the U-phase switch 61 and the W-phase switch 63. It is determined that This is because the switching devices 61 and 63 are in the Δ connection switching state even though the switching signal Sc is Low and the Y connection is designated thereby. Such a failure mode is referred to as an eleventh mode Mb11.

When the switching signal Sc is Low and the condition CQ6 is satisfied (when “only W phase is Y”), the unbalance detection unit 132c is caused by the failure of the U-phase switch 61 and the V-phase switch 62. It is determined that This is because the switching devices 61 and 62 are in the Δ connection switching state although the switching signal Sc is Low and the Y connection is designated by this. Such a failure mode is referred to as a twelfth mode Mb12.

Based on the switching state and the switching signal Sc described above, the process of identifying the failed switcher can be summarized as follows.
That is, when the Y connection is designated by the switching signal Sc, the unbalance detection unit 132c determines that the switch in the Δ connection switching state has failed, and the Δ connection is designated by the switching signal Sc. If the switch is in the Y connection switching state, it is determined that the switch has failed.

The above determination is shown in FIG.
As can be seen from the above description and FIG. 25, there are twelve failure modes Mb1 to Mb12, and the signal Sfb indicates which of these twelve failure modes Mb1 to Mb12.
The unbalance detection unit 132c sends a signal Sfb indicating the above determination result to the failure determination unit 133c.

Similarly to the failure determination unit 133 of the first embodiment, the failure determination unit 133c outputs a signal indicating the result of the failure determination based on the signal Sfb and the signal Sdf and a signal indicating the failed switcher. The failure determination unit 133c may output a signal indicating the connection designated by the switching signal Sc when a failure is detected, together with a signal indicating the switch that has failed.

For example, if the signal Sdf is High and the signal Sfb indicates one of the failure modes Mb1 to Mb12, as described in the first embodiment, the failure determination unit 133c switches to the switching device 60. It is determined that there is a failure.
When it is determined that there is a failure, the failure determination unit 133c sends a failure detection signal Sdg to the operation control unit 102.

When the failure detection signal Sdg is sent, the operation control unit 102 outputs the inverter stop signal St. In response to the stop signal St, the PWM generator 117 stops outputting the PWM signals Sm1 to Sm6. As a result, the inverter 30 stops outputting the AC voltage.

If the signal Sdf is High, the failure determination unit 133c generates a display control signal Sfc indicating a switch that has failed based on the signal Sfb, and supplies the display control signal Sfc to the failure indicator 87.
For example, when the signal Sfb indicates the failure mode Mb1, a signal indicating that the V-phase switch 62 and the W-phase switch 63 are broken is generated as the display control signal Sfc.
The failure determination unit 133c may also output a signal indicating the connection designated by the switching signal Sc when a failure is detected.

The failure indicator 87 displays the failed switch according to the display control signal Sfc indicating the failed switch.
In repairing, it is possible to identify the switch that has failed by looking at the display of the failure indicator 87, and therefore repair can be performed promptly.

When a signal indicating the connection designated by the switching signal Sc when a failure is detected is also output, the failure indicator 87 displays the switching state when the failure is detected. If the switching state when a failure is detected is also displayed, the failure can be repaired more quickly.

Even if the signal Sfb does not indicate any of the modes Mb1 to Mb12, if the signal Sdf is High, the failure detection signal Sdg may be High. In that case, although the failed switching device cannot be specified, the inverter can be stopped by detecting the failure, so that the motor can be prevented from being damaged and demagnetized.

As described above, according to the third embodiment, it is possible to quickly detect when the switching device 60 breaks down, stop the inverter, and prevent damage to the motor and demagnetization.
Further, if the failure mode or the failed switching device is displayed on the failure indicator, the failure switching device can be easily identified and repaired quickly.

Embodiment 4 FIG.
In the configuration of FIG. 2, a changeover switch is used as a changer of the connection changeover device 60. Instead, each switch may be configured by a combination of a normally closed switch and a normally open switch. A configuration example of the connection switching device in that case is shown in FIG.

In the configuration of FIG. 26, a combination of a normally closed switch 615 and a normally open switch 616 is used instead of the changeover switch of the changer 61, and a normally closed switch 625 and a normally open switch 626 are used instead of the changeover switch of the changer 62. The combination of the normally closed switch 635 and the normally open switch 636 is used instead of the selector switch of the selector 63.

As shown in the figure, when the normally closed switches 615, 625, 635 are closed (turned on) and the normally open switches 616, 626, 636 are opened (turned off), the motor is Y-connected, Contrary to the illustration, when the normally closed switches 615, 625, 635 are open and the normally open switches 616, 626, 636 are closed, the motor is Δ-connected.

As shown in FIG. 26, when each switcher is configured by a combination of a normally closed switch and a normally open switch, an electromagnetic contactor can be used as each switch. The magnetic contactor is suitable because it has a small conduction loss when turned on.

As shown in FIG. 26, when each switch is configured by a combination of a normally closed switch and a normally open switch, each switch includes silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga2O3), diamond, and the like. A semiconductor switch composed of a wide band gap semiconductor (WBG semiconductor) composed of These have low on-resistance, low loss, and little element heat generation. They can also perform the switching operation promptly.

Modified example.
In the first to fourth embodiments, the present invention is applied to an electric motor drive device that can switch the stator winding of the electric motor to Y connection or Δ connection.
The present invention can also be applied to an electric motor drive device in which connection switching is performed by another method.
For example, the present invention can also be applied to an electric motor drive device that uses two or more winding portions as windings for each phase and can be switched to either parallel connection or series connection.
In this case, both ends of each of the two or more winding portions constituting the winding of each phase can be connected to the outside of the electric motor, and the connection state is switched by the connection switching device.

Even in such a case, if there is a failure in the connection switching device, the current becomes unbalanced and is included in at least one of the exciting current component and the torque current component obtained by converting the three-phase current to the dq axis. Many harmonic components are included. If the amount of such harmonic components is large compared to the normal state, it can be determined that there is a failure in the connection switching device.

In the above first to fourth embodiments, diodes or the like are generally used as the rectifier elements 11 to 14 of the rectifier circuit 10; It may be configured to perform rectification by turning it on according to the polarity of the voltage (input AC voltage) supplied from the AC power supply 4.

The switching elements 311 to 316 of the inverter main circuit 310 are assumed to be IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs. However, as the switching elements 311 to 316, any switching element can be used. Such a thing may be used. In the case of the MOSFET, since it has a parasitic diode in structure, the same effect can be obtained without connecting the rectifying elements (321 to 326) for recirculation in parallel.

As materials constituting the rectifying elements 11 to 14 and the switching elements 311 to 316, not only silicon (Si) but also silicon carbide (SiC), gallium nitride (GaN), diamond, etc. which are wide band gap semiconductors are used. By configuring with, it becomes possible to further reduce the loss.

Note that the configuration described in the above embodiment is an example of the configuration of the present invention, and can be combined with another known technique, and a part thereof is omitted without departing from the gist of the present invention. It is also possible to change and configure it.

As described above, the present invention is suitable for an electric motor drive device including a connection switching device that switches connection of an electric motor, and a refrigeration cycle application device including the motor drive device.
Although an air conditioner has been described as an example of a refrigeration cycle application device, the present invention is not limited thereto, and can be applied to, for example, a refrigerator, a freezer, a heat pump water heater, and the like.

2, 2b, 2c motor drive device, 4 AC power supply, 7 motor, 8 reactor, 10 rectifier circuit, 20 capacitor, 30 inverter, 60 connection switching device, 80 control power generation circuit, 85 bus current detection means, 87 fault indicator , 91, 92, 93, 96, 97, 98 Current detection element, 100, 100b, 100c control device, 102 Operation control unit, 110, 110b, 110c Inverter control unit, 111 Current restoration unit, 112, 112c 3 phase 2 phase Conversion unit, 113 Excitation current command control unit, 114 Voltage command calculation unit, 115 Electrical angle phase calculation unit, 116 Two-phase three-phase conversion unit, 117 PWM generation unit, 130, 130c Failure detection unit, 131 Harmonic detection unit, 132 132c Equilibrium detection unit, 133, 133c failure determination unit, 900 refrigeration cycle, 902 four-way valve, 904 compressor, 906 indoor heat exchanger, 908 expansion valve, 910 outdoor heat exchanger, 1141, frequency estimation unit, 1142, 1144, 1146 subtraction Part, 1143, 1145, 1147 control part.

Claims (12)

1. An electric motor drive device for driving an electric motor having three-phase windings,
   A connection switching device for switching the connection state of the windings of the motor in response to a switching signal;
   An inverter for applying an alternating voltage having a variable frequency and voltage value to the motor;
   A current detection unit that detects a three-phase alternating current flowing in the motor; and a three-phase two-phase conversion unit that converts the three-phase alternating current into a torque current component and an excitation current component; and the inverter and the connection switching A control device for controlling the device,
   The electric motor drive device in which the inverter is stopped when the amount of harmonic components of at least one of the torque current component and the excitation current component is larger than when there is no failure in the connection switching device.
2. When at least one of the torque current component and the excitation current component, the amount of the harmonic component is not less than twice the maximum value of the amount of the harmonic component when there is no failure in the connection switching device, The electric motor drive device according to claim 1, wherein the inverter is stopped.
3. The connection switching device is for switching between star connection and delta connection,
   The connection switching device has three switchers provided corresponding to the three-phase windings, respectively.
   3. The electric motor drive device according to claim 1, wherein a signal indicating which of the three switching devices has failed is generated based on the unbalance of the three-phase alternating current.
4. The electric motor drive device according to claim 3, wherein the current detection unit detects a current flowing from the inverter into the winding of the electric motor as the three-phase alternating current flowing through the electric motor.
5. If the current of one of the three phases is at least a first threshold smaller than the current of one of the other two phases and at least the first threshold greater than the current of the other phase. The one phase switch is in a delta connection switch state and the other two phase switch is in a star connection switch state to generate a signal;
   The current of one phase of the three phases is smaller than the current of one phase of the other two phases by at least the first threshold, and the current of the one phase and the current of the other phase If the difference is less than the first threshold, a signal indicating that the one phase switch is in a star connection switch state and the other two phase switch is in a delta connection switch state. Generate
   When the star connection is specified by the switching signal, a signal indicating that the switch in the switching state for the delta connection is broken is generated.
   The electric motor drive device according to claim 4, wherein when the delta connection is designated by the switching signal, a signal indicating that the switch in the star connection switching state is broken is generated.
6. The electric motor drive device according to claim 3, wherein the current detection unit detects an electric current flowing through a winding of the electric motor as the three-phase alternating current flowing through the electric motor.
7. If the sum of the instantaneous values of the currents of the other two phases other than one of the three phases is smaller than the second threshold, the switch of the one phase is in the delta connection switching state. Yes, the other two-phase switch generates a signal indicating that it is in the star connection switching state,
   If the magnitude of the current of one of the three phases is smaller than a third threshold, the switch for one phase is in the star connection switching state and the switch for the other two phases is delta. Generate a signal indicating that it is in the connection switching state,
   When the star connection is specified by the switching signal, a signal indicating that the switch in the switching state for the delta connection is broken is generated.
   The electric motor drive device according to claim 6, wherein when the delta connection is designated by the switching signal, a signal indicating that the switch in the star connection switching state is broken is generated.
8. The electric motor drive device according to any one of claims 1 to 7, further comprising a failure indicator that displays that the connection switching device is out of order.
9. The connection switching device has a plurality of electromagnetic contactors,
   The electric motor drive device according to any one of claims 1 to 8, wherein each of the plurality of electromagnetic contactors includes an excitation coil and a contact driven by a current flowing through the excitation coil.
10. The connection switching device has a plurality of semiconductor switches,
    9. The electric motor drive device according to claim 1, wherein each of the plurality of semiconductor switches has a control terminal and is controlled by a signal input to the control terminal.
11. 11. The electric motor drive device according to claim 10, wherein the semiconductor switch is made of a wide band gap semiconductor.
12. A refrigeration cycle application device comprising the electric motor drive device according to any one of claims 1 to 11.

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