JP7123616B2 - motor drive - Google Patents

Description

The present invention relates to a motor drive device for driving a permanent magnet synchronous motor, a so-called open winding motor, having a plurality of phase windings that are not connected to each other.

A permanent magnet synchronous motor having a plurality of phase windings is used as a motor for driving a compressor mounted in a refrigeration cycle device such as an air conditioner or a heat source. As an example of this permanent magnet synchronous motor, there is known an open-windings motor in which a plurality of phase windings are disconnected from each other.

A motor driving device for driving this open winding motor includes a first inverter connected to one end of each phase winding, a second inverter connected to the other end of each phase winding, and a second inverter connected to the other end of each phase winding. A star connection mode is provided in which a switch is connected between each other, and when the switch is closed, each phase winding is star-connected and the motor is driven only by the first inverter. An open winding mode is selectively set in which the windings are open and the motor is driven by both the first inverter and the second inverter. For example, by setting the star connection mode in the low rotation speed range and the open winding mode in the high rotation speed range, a wide rotation speed range can be obtained and highly efficient operation is possible in the low rotation speed range. becomes.

Japanese Patent No. 4906836 JP 2017-93077 A

The open winding mode cannot be set if a short-circuit failure occurs in which the contacts of the switch do not open due to welding or other reasons.
An object of the embodiments of the present invention is to provide a motor drive device capable of accurately detecting a short-circuit failure of a switch.

A motor drive device according to claim 1 is a motor drive device for a motor having a plurality of phase windings that are not connected to each other, and comprises a first inverter, a second inverter, a switch, a controller, and detection means. The first inverter has a plurality of series circuits of upstream switching elements and downstream switching elements, both ends of these series circuits are connected to a DC power supply, and mutual A connection point is connected to one end of each of the phase windings. The second inverter has a plurality of series circuits of upstream switching elements and downstream switching elements, both ends of these series circuits are connected to the DC power supply, and the upstream switching elements and downstream switching elements of the series circuits An interconnection point is connected to the other end of each said phase winding. A switch is connected between the other ends of the windings of each phase, and is closed when energized and opened when deenergized . A controller controls opening and closing of the switch and operation of the first inverter and the second inverter. The detecting means deactivates the switch to turn on predetermined upstream switching elements and predetermined downstream switching elements in the second inverter, and the current flowing between the DC power supply and the second inverter causes the Detects switch short circuit faults.

The figure which shows the structure of the refrigerating-cycle apparatus which concerns on one Embodiment. 1 is a block diagram showing the configuration of an embodiment; FIG. 4 is a flowchart showing control of a motor controller in one embodiment; 4 is a time chart showing how a star connection mode and an open winding mode are selectively set when there is no abnormality in a relay contact in one embodiment. 4 is a flow chart showing an inspection mode routine in FIG. 3; The figure which shows the flow of an electric current when there is a short-circuit fault in the relay contact 51a at the time of the inspection mode of one Embodiment. The figure which shows the other example of the flow of an electric current when there is a short-circuit fault in the relay contact 51a at the time of the inspection mode of one Embodiment. The figure which shows the flow of an electric current when there is a short circuit fault in the relay contact 52a at the time of the inspection mode of one Embodiment. The figure which shows the other example of the flow of an electric current when the relay contact 52a has a short circuit failure at the time of the inspection mode of one Embodiment. The figure which shows the flow of an electric current when relay contacts 51a and 52a do not have an open fault at the time of the inspection mode of one Embodiment. The figure which shows the flow of an electric current when the relay contact 51a has an open failure at the time of the inspection mode of one Embodiment. The figure which shows the flow of an electric current when there exists an open failure in the relay contact 52a at the time of the inspection mode of one Embodiment. The figure which shows the state where an electric current does not flow when relay contacts 51a and 52a have an open failure at the time of inspection mode of one embodiment.

FIG. 1 shows the configuration of a refrigeration cycle device for an air conditioner according to one embodiment of the present invention.
One end of an outdoor heat exchanger 3 is pipe-connected via a four-way valve 2 to a discharge port of a compressor 1 having an open-winding motor 1M (hereinafter referred to as a motor 1M) as a drive motor, One end of an indoor heat exchanger 5 is pipe-connected to the other end of the outdoor heat exchanger 3 via an electric expansion valve 4 which is a pressure reducer. The other end of the indoor heat exchanger 5 is pipe-connected to the suction port of the compressor 1 via the four-way valve 2 .

An outdoor fan 6 is arranged near the outdoor heat exchanger 3 , and an indoor fan 7 is arranged near the indoor heat exchanger 5 . The motor 1M, the four-way valve 2, the electric expansion valve 4, the outdoor fan 6, and the indoor fan 7 are driven and controlled by the controller 10.
During cooling operation, the controller 10 causes the gas refrigerant discharged from the compressor 1 to flow through the four-way valve 2 to the outdoor heat exchanger 3, as indicated by the solid line arrow in FIG. The gas refrigerant that has flowed to the outdoor heat exchanger 3 releases heat to the outside air and condenses. The liquid refrigerant flowing out of the outdoor heat exchanger (condenser) 3 flows into the indoor heat exchanger 5 while being decompressed by the electric expansion valve 4 . The liquid refrigerant that has flowed into the indoor heat exchanger 5 takes heat from the indoor air and evaporates. Gas refrigerant flowing out of this indoor heat exchanger (evaporator) 5 passes through the four-way valve 2 and is sucked into the compressor 1 . During heating operation, the controller 10 switches the four-way valve 2 to flow the gas refrigerant discharged from the compressor 1 to the indoor heat exchanger 5 via the four-way valve 2 as indicated by the dashed arrow in FIG. The gas refrigerant that has flowed through the indoor heat exchanger 5 releases heat to the indoor air and condenses. The liquid refrigerant flowing out from the indoor heat exchanger (condenser) 5 is depressurized by the electric expansion valve 4 and flows to the outdoor heat exchanger 3 . The liquid refrigerant that has flowed to the outdoor heat exchanger 3 takes heat from the outside air and evaporates. Gas refrigerant flowing out of the outdoor heat exchanger (evaporator) 3 is sucked into the compressor 1 through the four-way valve 2 . A refrigerating cycle is formed by a compressor 1, a four-way valve 2, an indoor heat exchanger 5, an electric expansion valve 4 (a decompression device), an outdoor heat exchanger 3, and refrigerant pipes connecting them.

The motor drive device of the present embodiment, as shown in FIG. 2, includes a drive circuit and a part of the controller 10 connected to the motor 1M. The motor 1M is a permanent magnet synchronous motor having a plurality of, for example, three phase windings Lu, Lv, and Lw that are not connected to each other.
A diode bridge full-wave rectifier circuit 22 is connected to a three-phase AC power supply 20 via a noise filter 21 , and a capacitor 24 is connected to the output end of the full-wave rectifier circuit 22 via a reactor 23 . The full-wave rectifier circuit 22, the reactor 23, and the capacitor 24 constitute a DC power supply 25 that outputs a DC voltage Vdc.

An input end of an inverter (first inverter) 30 is connected to the DC power supply 25, and one ends of the phase windings Lu, Lv, and Lw are connected to the output end of the inverter 30. FIG. An input end of an inverter (second inverter) 40 is connected to the DC power supply 25, and an output end of the inverter 40 is connected to the other ends of the phase windings Lu, Lv, and Lw. A common power supply system is adopted in which the inverters 30 and 40 are connected to the same DC power supply 25 . The inverter 30 is also called a primary side inverter or a master inverter, and the inverter 40 is also called a secondary side inverter or a slave inverter.

The inverter 30 has an upstream switching element IGBT 31u and a downstream switching element IGBT 32u connected in series. The connected U-phase series circuit, the IGBT 31v of the upstream switching element and the IGBT 32v of the downstream switching element are connected in series, and both ends are connected to the DC power supply 25, and the interconnection point of the IGBTs 31v and 32v is the phase winding of the motor 1M. A V-phase series circuit connected to one end of Lv, an IGBT 31w of an upstream switching element and an IGBT 32w of a downstream switching element are connected in series, both ends of which are connected to a DC power supply 25, and an interconnection point of the IGBTs 31w and 32w is a motor 1M. The DC voltage Vdc of the DC power supply 25 is converted into a three-phase AC voltage of a predetermined frequency by switching the IGBTs 31u to 32w, and the three-phase AC voltage is converted to the motor 1M phase windings Lu, Lv and Lw are supplied to one end of each. A regeneration diode (also called a free wheel diode) D is connected in anti-parallel to each of the IGBTs 31u to 32w.

The inverter 40 has an upstream switching element IGBT 41u and a downstream switching element IGBT 42u connected in series, both ends of which are connected to the DC power supply 25, and the interconnection point of the IGBTs 41u and 42u is the other end of the phase winding Lu of the motor 1M. IGBT 41v of the upstream switching element and IGBT 42v of the downstream switching element are connected in series, and both ends are connected to the DC power supply 25, and the interconnection point of the IGBTs 41v and 42v is the phase winding of the motor 1M. The V-phase series circuit connected to the other end of the line Lv, the IGBT 41w of the upstream switching element and the IGBT 42w of the downstream switching element are connected in series, both ends are connected to the DC power supply 25, and the interconnection point of the IGBTs 41w and 42w is It includes a W-phase series circuit connected to the other end of the phase winding Lw of the motor 1M, converts the DC voltage Vdc of the DC power supply 25 into a three-phase AC voltage of a predetermined frequency by switching the IGBTs 41u to 42w, and converts the three-phase AC voltage. A voltage is supplied to each other end of the phase windings Lu, Lv, Lw of the motor 1M. A regeneration diode (also called a free wheel diode) D is connected in anti-parallel to each of the IGBTs 41u to 42w.

Since the voltage applied to the windings of the motor 1M can be increased, the motor 1M can be rotated at high speed. However, if the motor 1M is driven by the two inverters 30 and 40, the power consumption will increase and the efficiency will decrease. Therefore, it is preferable to drive the motor 1M with only one inverter 30 by star-connecting the windings of each phase of the motor 1M in the low rotational speed region, thereby improving the efficiency. Furthermore, when the motor 1M is operated in a low rotation speed range, the wire diameter of each phase winding of the motor 1M is reduced to increase the number of turns of each phase winding, thereby increasing the winding density, thereby improving the efficiency of the motor 1M. Connect. From this point of view as well, it is preferable to appropriately switch the phase windings Lu, Lv, and Lw between the open winding state and the star connection state. Therefore, a normally open contact (relay contact) 51a of a switch, such as a relay 51, is connected between the other end of the phase winding Lu and the other end of the phase winding Lv of the motor 1M. A normally open contact (referred to as a relay contact) 52a of a switch such as a relay 52 is connected between the other end of the line Lv and the other end of the phase winding Lw. When the relay contacts 51a, 52a are closed, the other ends of the phase windings Lu, Lv, Lw are interconnected to star-connect the phase windings Lu, Lv, Lw. When the relay contacts 51a and 52a are opened, the other ends of the phase windings Lu, Lv and Lw are opened, and the phase windings Lu, Lv and Lw are electrically isolated from each other, resulting in an open winding state.

Current sensors 53, 53v, 53w are arranged in three current lines between the inverter 30 and the phase windings Lu, Lv, Lw of the motor 1M. be done. A current sensor 54 is arranged on one of the positive energization line P<b>1 and the negative energization line P<b>2 between the DC power supply 25 and the inverter 40 , and the detection signal of this current sensor 54 is sent to the controller 10 .

The controller 10 includes a main controller 10a that controls the refrigeration cycle apparatus, a voltage detector 61 that detects the output voltage Vdc of the DC power supply 25, and current sensors 53, 53v, and 53w that detect the current flowing through each phase winding of the motor 1M. A current detection unit 62 for detecting a current, a relay driving unit 63 for driving the relays 51 and 52, a display unit 64, and a motor controller 60 are included.

The motor controller 60 controls the opening and closing of the relay contacts 51a and 52a, the operation of the inverter 30, and the operation of the inverter 40 in accordance with the control of the main controller 10a, the voltage detected by the voltage detector 61, the current detected by the current detector 62, and the like. do.
In particular, the motor controller 60 has, as main functions, an abnormality detection section (detection means) 60a and a mode setting section 60b.

The abnormality detection unit 60a conducts a predetermined upstream switching element and a predetermined downstream switching element in the inverter 40, and detects a short circuit failure of the relay contacts 51a and 52a based on the presence or absence of a current Io flowing between the DC power supply 25 and the inverter 40. The relay contacts 51a and 52a are opened depending on the magnitude (including presence/absence) of the current flowing through the phase windings Lu, Lv, and Lw by conducting predetermined upstream switching elements and predetermined downstream switching elements in the inverter 30. Detect faults.

The mode setting unit 60b provides a star connection mode in which the other ends of the phase windings Lu, Lv, and Lw are interconnected by closing the relay contacts 51a and 52a and the inverter 30 is operated alone, and a star connection mode in which the relay contacts 51a and 52a are opened. The open winding mode in which the other ends of the phase windings Lu, Lv, and Lw are opened and the inverters 30 and 40 are connected to each other by the detection result of the detection unit 60a and the load of the refrigeration cycle device (air conditioning load) Selectively set according to

[Description of overall control]
Next, the overall control executed by the motor controller 60 will be described with reference to the flow chart of FIG. 3 and the time chart of FIG. Steps S1, S2, . . . of the flowchart are abbreviated as S1, S2, .
When the motor controller 60 receives an operation start command from the main controller 10a (YES in S1), the motor controller 60 executes an inspection mode routine for detecting abnormalities (short circuit failure and open failure) of the relay contacts 51a and 52a (S2). . Specific processing of this inspection mode routine will be described later.

If no abnormality is detected in the relay contacts 51a and 52a in the inspection mode routine (YES in S3), the motor controller 60 sets the abnormality flag f to "0" (S4) and sets the star connection mode (S5). ). The star connection mode is an operation in which the relay contacts 51a, 52a are closed to interconnect the other ends of the phase windings Lu, Lv, Lw, and the inverter 30 is operated alone (inverter 40 is stopped). . After setting the star connection mode, the motor controller 60 applies a predetermined DC excitation current from the inverter 30 to the phase windings Lu, Lv, and Lw to rotate the rotor of the motor 1M to a specified position (angle). DC excitation (so-called "initial positioning") is executed (S10).

If an abnormality is detected in either one of the relay contacts 51a and 52a in the inspection mode routine (NO in S3), the motor controller 60 notifies the content of the abnormality by character display or image display on the display unit 64 (S6). , the abnormality flag f is set to "1" (S7). Then, the remote controller 60 determines whether the abnormality is a short-circuit failure or an open-circuit failure (S8).

If at least one of the relay contacts 51a and 52a has a short-circuit fault that does not open due to welding or the like (YES in S8), the motor controller 60 proceeds to the process of S5, and the star connection that can be set even in the case of a short-circuit fault. A mode is set (S5).
If at least one of the relay contacts 51a and 52a remains open and does not close (NO in S8), the remote controller 60 sets an open winding mode that can be set even in an open failure (S9). The open winding mode is an operation mode in which the relay contacts 51a and 52a are opened to open the other ends of the phase windings Lu, Lv and Lw, and the inverters 30 and 40 are connected to each other. After setting the open winding mode, the motor controller 60 proceeds to the process of S10 and executes "DC excitation" (S10).

That is, even if a short-circuit failure occurs in either of the relay contacts 51a and 52a, the motor 1M can be started by setting the star connection mode. Further, even if an open failure occurs in one of the relay contacts 51a and 52a, the motor 1M can be started by setting the open winding mode. Since the short-circuit failure and open-circuit failure are notified by the character display and image display on the display unit 64, the occurrence of the short-circuit failure and open-circuit failure can be accurately notified to the user.

After continuing the "DC excitation" for a certain period of time t1 (YES in S11), the motor controller 60 applies the field component current from the inverter 30 to the phase windings Lu, Lv, Lw to forcibly pull the rotor. commutation” is executed (S12). After continuing this “forced commutation” for a certain period of time t2 (YES in S13), the motor controller 60 reduces the field component current while supplying the gradually increasing torque component current from the inverter 30 to the phase windings Lu and Lv. , Lw to increase the rotation speed N of the rotor. Detected by the unit 62, the rotation speed N of the rotor is estimated from the detected current value, and the switching of the inverter 30 is performed by PWM (Pulse Width Modulation) so that the estimated rotation speed N becomes the target rotation speed Nt according to the air conditioning load. control (S14).

Subsequently, the motor controller 60 checks the abnormality flag f (S15). When the abnormality flag f is "0" (YES in S15), that is, when there is no abnormality in the relay contacts 51a and 52a, the motor controller 60 determines whether the rotation speed N of the motor 1M has increased to the threshold value N2 (<Nt). is determined (S16). While the rotational speed N is increasing toward the threshold value N2 (NO in S16, NO in S19), the process returns to the above 14, and the inverter 30 is operated to increase the rotational speed N to the target rotational speed Nt corresponding to the air conditioning load. PWM control of switching is continued (S14).

In the star connection mode in which the other ends of the phase windings Lu, Lv, and Lw are interconnected, the zero-phase current (also referred to as zero-axis current), which causes a decrease in efficiency, does not flow in the phase windings Lu, Lv, and Lw. , the motor 1M can be started with high efficiency.
When the rotation speed N increases and reaches the threshold value N2 (high rotation speed region; YES in S16), the motor controller 60 keeps the rotation speed N constant at the threshold value N2 for a certain period of time ts (S17). The motor controller 60 sets the open winding mode while the rotational speed N is kept constant at the threshold value N2 (S18). Then, if the motor controller 60 has not received an operation stop command from the main controller 10a (NO in S22), the motor controller 60 returns to the process of S14, and controls the inverter so that the rotation speed N becomes the target rotation speed Nt according to the air conditioning load. The switching of the IGBTs 31-36 of the inverter 40 and the switching of the IGBTs 41-46 of the inverter 40 are interconnected and PWM-controlled (S14). By setting the open winding mode, it is possible to apply a high level voltage to the phase windings Lu, Lv, and Lw, which is almost twice as high as in the star connection mode. As a result, it is possible to exhibit a sufficient compression function that can cope with high-load operation.

When the rotation speed N decreases and reaches the threshold value N1 (low rotation speed region; NO in S16, YES in S19), the motor controller 60 keeps the rotation speed N constant at the threshold value N1 for a certain time ts (S20). . While the rotational speed N is kept constant at the threshold value N1, the motor controller 60 closes the relay contacts 51a and 52a to interconnect the other ends of the phase windings Lu, Lv and Lw and causes the inverter 30 to operate alone. A star connection mode is set (S21). Then, if the motor controller 60 has not received an operation stop command from the main controller 10a (NO in S22), the motor controller 60 returns to the process of S14, and controls the inverter so that the rotation speed N becomes the target rotation speed Nt according to the air conditioning load. The switching of the IGBTs 31 to 36 of 30 is PWM-controlled (S14). By setting the star connection mode, it is possible to apply a low-level voltage to the phase windings Lu, Lv, Lw, which can correspond to low-load operation.

When the operation stop command is received from the main controller 10a (YES in S22), the motor controller 60 stops all the operations of the inverters 30 and 40 (S23).
When switching between the star-shaped connection mode and the open winding mode, the number of revolutions N is kept constant at the threshold value N2 or at the threshold value N1 over a certain period of time ts because of the drive control of the inverters 30 and 40 and the actual operation of the motor 1M. This is to prevent so-called out-of-synchronization in which synchronization with rotation is lost. At least one second or more is ensured as the fixed time ts.

In the determination of S15, if the abnormality flag f is "1" (NO in S15), that is, if there is an abnormality in either of the relay contacts 51a and 52a, the motor controller 60 switches the mode by the processing of S16 to S21. (S22), while maintaining the current star connection mode setting or open winding mode setting. If the operation stop command has not been received (NO in S22), the process returns to S14 while maintaining the current star connection mode setting or open winding mode setting, and the rotation speed N is set to the target corresponding to the air conditioning load. The switching of the IGBTs 31 to 36 of the inverter 30 is PWM-controlled so that the rotational speed becomes Nt (S14). When the operation stop command is received from the main controller 10a (YES in S22), the motor controller 60 stops all the operations of the inverters 30 and 40 (S23).

[Description of inspection mode routine]
The processing of the inspection mode routine in S2 will be described with reference to the flow chart of FIG. 5 and FIGS. 6 to 13. FIG.
(1) Detection of short circuit failure The motor controller 60 deactivates the relays 51 and 52 in order to detect a short circuit failure of the relay contacts 51a and 52a (S31). Subsequently, the motor controller 60 causes the IGBT 41u as a predetermined upstream switching element and the IGBT 42v as a predetermined downstream switching element in the secondary inverter 40 to conduct U-phase-V-phase energization (1-phase-1-phase energization). ), or perform V-phase-U-phase energization (1-phase-1-phase energization) to conduct the IGBT 41v as a predetermined upstream switching element and the IGBT 42u as a predetermined downstream switching element in the inverter 40 on the secondary side ( S32), the presence or absence of the current Io flowing through the power lines P1 and P2 between the DC power supply 25 and the inverter 40 is monitored via the current sensor 54 (S33).

If the relay contacts 51a and 52a are reliably opened in response to the deenergization of the relays 51 and 52, the current Io does not flow through the positive energization line P1 and the negative energization line P2 between the DC power supply 25 and the inverter 40 (Io = 0).
If the relay contact 51a does not open due to, for example, welding even though the relay 51 is de-energized, and the relay contact 52a is surely opened in response to the de-energization of the relay 52, the U-phase-V-phase energization can be executed. If there is, as shown in FIG. 6, a current Io flows between the DC power supply 25 and the inverter 40 along a path passing through the positive-side conducting line P1→IGBT 41u→relay contact 51a→IGBT 42v→negative-side conducting line P2 (Io> 0). In the case of execution of the V-phase-U-phase energization, as shown in FIG. A current Io flows between (Io>0).

When the current Io flows between the DC power supply 25 and the inverter 40 (Io>0; YES in S33), the motor controller 60 determines that the relay contact 51a is short-circuited (S34), and proceeds to the next process. Transition. If the current Io does not flow (Io=0; NO in S33), the motor controller 60 bypasses the determination in S34 and proceeds to the next process.

Subsequently, the motor controller 60 conducts V-phase-W-phase energization (1-phase-1-phase energization) to conduct the IGBT 41v as a predetermined upstream switching element and the IGBT 42w as a predetermined downstream switching element in the secondary inverter 40. ), or W-phase-V-phase energization (1-phase-1-phase energization) that conducts the IGBT 41w as a predetermined upstream switching element and the IGBT 42v as a predetermined downstream switching element in the secondary inverter 40 ( S35), the presence or absence of the current Io flowing through the power lines P1 and P2 between the DC power supply 25 and the inverter 40 is monitored via the current sensor 54 (S36).

If the relay contact 52a does not open due to welding or the like even though the relay 52 is deenergized, and the relay contact 51a is surely opened in response to the deenergization of the relay 51, the V phase-W phase energization can be executed. If there is, as shown in FIG. 8, a current Io flows between the DC power supply 25 and the inverter 40 along a path passing through the positive-side conducting line P1→IGBT 41v→relay contact 52a→IGBT 42w→negative-side conducting line P2 (Io> 0). In the case of executing the W-phase-V-phase energization, as shown in FIG. A current Io flows between (Io>0).

When the current Io flows between the DC power supply 25 and the inverter 40 (Io>0; YES in S36), the motor controller 60 determines that the relay contact 52a has a short-circuit fault (S37), and the following open fault occurs. to the detection process. If the current Io does not flow (Io=0; NO in S36), the motor controller 60 bypasses the determination in S37 and proceeds to the next open circuit failure detection process.

(2) Detection of open failure Following the process of detecting a short circuit failure, the motor controller 60 energizes the relays 51 and 52 to detect an open failure of the relay contacts 51a and 52a (S38). Then, the motor controller 60 conducts V-phase-U-phase/W-phase energization (1-phase -2-phase energization) is executed (S39), and the magnitudes of the currents Iu, Iv, Iw flowing through the phase windings Lu, Lv, Lw are monitored via the current sensors 53u, 53v, 53w (S40, S41, S43 , S45).

If the relay contacts 51a and 52a are reliably closed in response to the energization of the relay contacts 51 and 52, as shown in FIG. The current Iv that has passed through the phase winding Lv is diverted to the relay contact 51a side to become the current Iu that flows from the phase winding Lu→IGBT 32u→negative-side conducting line P2, and the current Iv that has passed through the phase winding Lv flows to the relay contact 52a side. is also split to become a current Iw from the phase winding Lw→IGBT 32w→negative side conducting line P2.

In this case, if the element resistance of the IGBTs 31v, 32u, 32w is ignored, the value of the current Iv is determined according to the sum of the resistance value of the phase winding Lv and the combined resistance value of the parallel circuit of the phase windings Lu, Lw. and becomes equal to or greater than a predetermined set value Ivs (Iv≧Ivs). The values of currents Iu and Iw are both greater than zero (Iu>0; Iw>0).

If the current Iv is greater than or equal to the set value Ivs (YES in S40), the motor controller 60 concludes that there is no open failure in the relay contacts 51a and 52a, and terminates the inspection routine.
When the relay contact 51a is not closed despite the energization of the relay 51, and the relay contact 52a is surely closed in response to the energization of the relay 52, as shown in FIG. →The current Iv flows through the path through the phase winding Lv, and the current Iv that has passed through the phase winding Lv is not split to the relay contact 51a, but is split only to the relay contact 52a. The current Iw reaches the line P2.

In this case, if the element resistances of the IGBTs 31v, 32u, and 32w are ignored, the value of the current Iv increases to a magnitude determined according to the sum of the resistance value of the phase winding Lv and the resistance value of the phase winding Lw. It becomes smaller than the set value Ivs (Iv<Ivs). The value of the current Iu becomes zero (Iu=0) and the value of the current Iw becomes greater than zero (Iw>0).

When the current Iv is less than the set value Ivs and greater than zero (NO in S40, NO in S41) and the current Iu is zero (YES in S42), the motor controller 60 determines that the relay contact 51a has an open failure. (S43), the inspection routine is terminated.
Conversely, when the relay contact 52a is not closed despite the energization of the relay 52, and the relay contact 51a is surely closed in response to the energization of the relay 51, as shown in FIG. The current Iv flows through the path P1→IGBT 31v→phase winding Lv, and the current Iv passing through the phase winding Lv is not split to the relay contact 52a side, but is split only to the relay contact 51a side, and the phase winding Lu→IGBT 32u. →The current Iu reaches the negative-side conducting line P2.

In this case, if the element resistances of the IGBTs 31v, 32u, and 32w are ignored, the value of the current Iv increases to a magnitude determined according to the sum of the resistance value of the phase winding Lv and the resistance value of the phase winding Lu. It becomes smaller than the set value Ivs (Iv<Ivs). The value of the current Iu becomes greater than zero (Iu>0) and the value of the current Iw becomes zero (Iw=0).

When the current Iv is less than the set value Ivs and greater than zero (NO in S40, NO in S41) and the current Iu is greater than zero and the current Iw is zero (NO in S42), the motor controller 60 sets the relay contact 52a. is an open failure (S44), and the inspection routine ends.

If both relay contacts 51a and 52a do not close despite the energization of relays 51 and 52, current Iv does not flow (Iv=0), as shown in FIG.
If the current Iv is zero (NO in S40, YES in S41), the motor controller 60 determines that both the relay contacts 51a and 52a have an open failure (S45), and terminates the inspection routine.

As described above, the short-circuit failure and open-circuit failure of the relay contacts 51a and 52a can be accurately detected.
[Modification]
In the above-described embodiment, the case where the switches are the relay contacts 51a and 52a has been described as an example, but a semiconductor switch can be used as the switch in the same way.
In the above embodiment, an open winding motor used as a motor for driving a compressor has been described as an example, but an open winding motor used for other purposes can also be implemented in the same manner.

In the above embodiment, the DC power supply 25 composed of the full-wave rectifier circuit 22, the reactor 23, and the capacitor 24 is used.
In addition, the above embodiments and modifications are presented as examples and are not intended to limit the scope of the invention. The novel embodiments and modifications can be implemented in various other forms, and various omissions, rewrites, and modifications can be made without departing from the scope of the invention. These embodiments and modifications are included in the scope of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 1... Compressor 1M... Open winding motor Lu, Lv, Lw... Phase winding 2... Four-way valve 3... Outdoor heat exchanger 4... Electric expansion valve 5... Indoor heat exchanger 10... Controller , 10a Main controller 20 Three-phase AC power supply 22 Full-wave rectifier circuit 24 Capacitor 25 DC power supply 30 Inverter (first inverter) 40 Inverter (second inverter) 51, 52 Relay 51a, 52a Relay contact 53u, 53v, 53w Current sensor 60 Motor controller 61 Voltage detector 62 Current detector 63 Neutral point potential detector 64 Relay driver

Claims (6)

A motor drive device for a motor having a plurality of phase windings that are not connected to each other,
A plurality of series circuits of upstream switching elements and downstream switching elements are provided, both ends of the series circuits are connected to a DC power supply, and interconnection points of the upstream switching elements and downstream switching elements of the series circuits are the respective a first inverter connected to one end of the phase winding;
A plurality of series circuits of upstream switching elements and downstream switching elements are provided, both ends of the series circuits are connected to the DC power supply, and an interconnection point between the upstream switching elements and the downstream switching elements of each series circuit is the a second inverter connected to the other end of each phase winding;
a switch connected between the other ends of the respective phase windings and closed when energized and opened when deenergized;
a controller that controls opening and closing of the switch and operation of the first inverter and the second inverter;
deenergizing the switch to turn on a predetermined upstream switching element and a predetermined downstream switching element in the second inverter, and short-circuiting the switch due to a current flowing between the DC power supply and the second inverter; a detection means for detecting a failure;
A motor drive device comprising: The detection means energizes the switch to conduct predetermined upstream switching elements and predetermined downstream switching elements in the first inverter, and the current flowing through each phase winding causes an open failure of the switch. 2. The motor drive device according to claim 1, characterized by detecting: The controller operates in a star connection mode in which the other ends of the windings of each phase are interconnected by closing the switches and the first inverter is operated alone, and the windings of the phases are connected to each other by opening the switches. 3. An open winding mode in which the other end is opened and the first and second inverters are interconnected is selectively set according to the detection result of the detection means and the load. A motor drive as described. The controller is
performing detection by the detection means before starting the motor;
When the detecting means does not detect the short-circuit fault and the open-circuit fault, a star-connection mode is set in which the other ends of the windings of each phase are interconnected by closing the switch and the first inverter is operated alone. After this start, the other end of each phase winding is opened by the star connection mode and the opening of the switch, and the first and second inverters are connected to each other. Selectively set the open winding mode according to the load,
when the short-circuit failure is detected by the detection means, the star connection mode is set to start the motor, and the star connection mode setting is continued after the start, and
3. When the open circuit fault is detected by the detecting means, the open winding mode is set to start the motor, and the setting of the open winding mode is continued even after the start. The motor drive device according to . The motor has three phase windings Lu, Lv, Lw,
The plurality of series circuits of the first inverter include a U -phase series circuit in which an interconnection point between an upstream switching element and a downstream switching element is connected to one end of the phase winding Lu, an upstream switching element and a downstream switching element. is connected to one end of the phase winding Lv, and a W-phase series circuit is connected to one end of the phase winding Lw at the mutual connection point of the upstream switching element and the downstream switching element. and
The plurality of series circuits of the second inverter include a U -phase series circuit in which an interconnection point between an upstream switching element and a downstream switching element is connected to the other end of the phase winding Lu, an upstream switching element and a downstream switching element. A V-phase series circuit in which the interconnection point of the elements is connected to the other end of the phase winding Lv, and a W-phase circuit in which the interconnection point of the upstream switching element and the downstream switching element is connected to the other end of the phase winding Lw. is a phase-series circuit,
The switch is connected between the other end of the phase winding Lu and the other end of the phase winding Lv, a first switch that is closed when energized and opened when deenergized, and the other end of the phase winding Lv. and a second switch connected between the other end of the phase winding Lw and closed when energized and opened when deenergized,
The detection means deactivates the first switch and the second switch to switch the upstream switching element of one series circuit in the second inverter and the downstream switching of one series circuit other than the series circuit. A short-circuit failure of the first switch and a short-circuit failure of the second switch are detected by conducting an element and detecting presence/absence of current flowing between the DC power supply and the second inverter. 2. The motor driving device according to 1. The detection means energizes the first switch and the second switch to switch the upstream switching element of the V-phase series circuit, the downstream switching element of the U-phase series circuit, and the W-phase series circuit in the first inverter. 6. The open-circuit failure of the first switch and the second switch is detected based on the magnitude of the current flowing through the phase windings Lu, Lv, and Lw when the downstream side switching elements are turned on. A motor drive as described.

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