WO2022009270A1 - Motor driving device and air-conditioning apparatus - Google Patents

Abstract

This motor driving device (100) has first and second switching modes which are selected on the basis of mode selection information when a motor (1) is driven by inverters (3a, 3b). In the first switching mode, on/off timings of the respective switching elements in identical phases in the inverters (3a, 3b) are matched between the inverters (3a, 3b), and a switching operation is performed for each of the inverters (3a, 3b). In the second switching mode, on/off timings of the respective switching elements in identical phases in the inverters (3a, 3b) are made different between the inverters (3a, 3b), and the switching operation is performed for each of the inverters (3a, 3b).

Description

Motor drive and air conditioner

The present disclosure relates to a motor drive device for driving a motor and an air conditioner provided with the motor drive device.

As a motor driving device for driving one motor by a plurality of inverters, there is one shown in Patent Document 1 below. This Patent Document 1 discloses a technique of controlling the current so as to maintain the balance of the inverter current, which is the output current of each inverter, that is, the output equilibrium so as not to concentrate the load on a specific inverter.

Japanese Patent No. 5447400

However, in the technique described in Patent Document 1, it is necessary to provide a current detector for detecting the inverter current in each inverter for each inverter and a current detector for detecting the motor current flowing in each phase of the motor. Therefore, there is a problem that the number of current detectors is large and the manufacturing cost increases.

Further, in the technique described in Patent Document 1, the difference or change in the environment in which each inverter is arranged is not taken into consideration. These differences or changes in the environment increase with the passage of time, and appear as variations in wiring resistance due to changes in the wiring temperature between the inverter and the motor, or changes in the state of the motor. Further, the difference or change in the environment in which each inverter is arranged fluctuates the cooling capacity of each inverter, and appears as the temperature variation of the switching element in each inverter. Therefore, there is a problem that a desired inverter output cannot be obtained even if the switching operation of the inverters is performed by aligning the on / off timings of the switching elements of the plurality of inverters with each other in the same phase of each inverter.

The present disclosure has been made in view of the above, and is a motor capable of suppressing fluctuations in inverter output due to differences or changes in the environment in which each inverter is arranged while reducing the number of current detectors. The purpose is to obtain a drive device.

In order to solve the above-mentioned problems and achieve the object, the motor drive device according to the present disclosure includes a plurality of inverters that convert a DC voltage supplied from a power source into a three-phase AC voltage and apply it to the same motor. It is a motor drive device. The motor drive device has first and second switching modes that are selected based on the mode selection information when the motor is driven by a plurality of inverters. In the first switching mode, the switching operation of each inverter is performed by aligning the on and off timings of the switching elements in the same phase of each inverter among the plurality of inverters. In the second switching mode, the switching operation of each inverter is performed by setting the on / off timing of the switching element in the same phase of each inverter to be different among the plurality of inverters.

According to the motor drive device according to the present disclosure, it is possible to reduce the number of current detectors and suppress the fluctuation of the inverter output due to the difference or change in the environment in which each inverter is arranged.

A circuit diagram showing a configuration example of the motor drive device according to the first embodiment. The figure which shows the 1st configuration example of the electric power source shown in FIG. The figure which shows the 2nd configuration example of the electric power source shown in FIG. A time chart showing an example of a PWM signal which is a switching command when each inverter in the first embodiment is driven in the first switching mode. A time chart showing an example of a PWM signal which is a switching command when each inverter in the first embodiment is driven in the second switching mode. A flowchart used to explain the method of selecting the switching mode in the first embodiment. A block diagram showing an example of a hardware configuration that realizes the function of the control unit in the first embodiment. A block diagram showing another example of a hardware configuration that realizes the function of the control unit in the first embodiment. A circuit diagram showing the configuration of the motor drive device according to the second embodiment. A flowchart used to explain the method of selecting the switching mode in the second embodiment. A circuit diagram showing the configuration of the motor drive device according to the third embodiment. A flowchart used to explain the method of selecting the switching mode in the third embodiment. A circuit diagram showing a configuration example of the motor drive device according to the fourth embodiment. The figure which shows the structural example of the air conditioner which concerns on Embodiment 5.

The motor drive device and the air conditioner according to the embodiment of the present disclosure will be described in detail with reference to the attached drawings below. In the following description, a plurality of components of the same type are indicated by reference numerals, but if the individual components are not distinguished, the notation of the subscripts will be omitted as appropriate. Further, in the following, the description will be simply referred to as "connection" without distinguishing between an electrical connection and a physical connection.

Embodiment 1.
FIG. 1 is a circuit diagram showing a configuration example of the motor drive device 100 according to the first embodiment. The motor drive device 100 is a drive device that uses the electric power supplied from the power source 2 to apply an AC voltage to the motor 1 connected to the load 6 to drive the load 6 connected to the motor 1.

As shown in FIG. 1, the motor drive device 100 according to the first embodiment includes inverters 3a and 3b, a control unit 4, and a current detection unit 5a and 5b. The control unit 4 controls the operation of the inverters 3a and 3b. Each of the current detection units 5a and 5b detects the inverter current flowing through each of the inverters 3a and 3b. In the case of the configuration of FIG. 1, the inverter current is the output current output from each of the inverters 3a and 3b to the motor 1. In the first embodiment, as shown in FIG. 1, a configuration having two inverters 3a and 3b will be described, but the configuration is not limited to this. The motor drive device 100 according to the first embodiment can be similarly applied even if the number of inverters 3 is 3 or more.

Next, the motor 1 and the power source 2 connected to the motor drive device 100 will be described. First, the motor 1 is a three-phase motor. An example of a three-phase motor is a three-phase permanent magnet synchronous motor. The motor 1 is connected to the load 6 via a motor shaft (not shown). An example of the load 6 is a compressor of an air conditioner. When the load 6 is a compressor, the motor 1 drives the compression element of the compressor.

FIG. 2 is a diagram showing a first configuration example of the power source 2 shown in FIG. FIG. 3 is a diagram showing a second configuration example of the power source 2 shown in FIG. FIG. 2 shows a three-phase AC / DC converter 22a provided with a three-phase converter, a reactor and a capacitor for converting AC power supplied from the three-phase AC power supply 21a into DC power. FIG. 3 shows a single-phase AC-DC converter 22b provided with a single-phase converter, a reactor and a capacitor for converting AC power supplied from the single-phase AC power supply 21b into DC power. The power source 2 may be configured by using any of these. Although not shown in FIGS. 2 and 3, a well-known booster circuit such as a DC converter is inserted into the DC bus between the AC / DC converters 22a and 22b and the respective inverters 3a and 3b to direct current. It may be configured to boost the voltage.

Further, a DC power source such as a battery or a battery that directly supplies a DC voltage to each of the inverters 3a and 3b may be used. The AC / DC converters 22a and 22b, or the booster circuit described above, may be configured to be incorporated in the motor drive device 100 instead of the power source 2. Further, although the configuration shown in FIG. 1 shows a configuration in which the inverters 3a and 3b are connected to the same power source 2, a configuration in which the respective inverters 3a and 3b are connected to different power sources 2 may be used.

Next, the inverters 3a and 3b will be described. The inverters 3a and 3b are connected in parallel to the same motor 1. Each of the inverters 3a and 3b converts the DC voltage supplied from the power source 2 into a three-phase AC voltage, and applies the converted three-phase AC voltage to the same motor 1. The three-phase AC voltage is a drive voltage for driving the motor 1 to rotate at a desired frequency, that is, at a desired rotation speed. The three-phase AC voltage is generated according to a three-phase pulse width modulation (PWM) signal. The PWM signal is generated by the control unit 4 based on the voltage command of each phase. In this specification, each phase of the three phases is represented by "U" or "u", "V" or "v" and "W" or "w", and each phase is represented by "U phase" or "V phase". And "W phase".

The inverter 3a includes six switching elements UP1, UN1, VP1, VN1, WP1, WN1. The switching elements UP1 and UN1 are connected in series to form a U-phase leg. The switching elements VP1 and VN1 are connected in series to form a V-phase leg. The switching elements WP1 and WN1 are connected in series to form a W-phase leg. These three legs are connected in parallel with each other to form a well-known three-phase inverter. Each switching element of the inverter 3a is controlled to be turned on or off according to a switching signal generated based on the above-mentioned PWM signal.

The inverter 3b includes six switching elements UP2, UN2, VP2, VN2, WP2, WN2. The inverter 3b is also configured in the same manner as the inverter 3a. Since the contents are duplicated, the explanation here is omitted.

A feedback diode is connected in parallel to each of the switching elements. When each switching element is a metal oxide semiconductor field effect transistor (Metal Oxide Semiconductor Field Effect Transistor: MOSFET), a parasitic diode contained in the MOSFET itself may be used as a feedback diode. Parasitic diodes are also called body diodes. The switching element is not limited to the MOSFET, and a switching element other than the MOSFET may be used.

Each switching element may be an element made of silicon (Si) or a wide bandgap semiconductor such as silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga ₂ O _{3) or diamond (C).} A wide band gap (WBG) semiconductor element may be used. If a WBG semiconductor element is used, the effects of low loss, high withstand voltage and high heat resistance can be enjoyed. Further, if a WBG semiconductor element is used, on / off operation can be performed at high speed. As a result, the on / off timing of switching can be finely controlled, so that the effect of the first embodiment, which will be described later, can be further enhanced.

FIG. 1 illustrates a configuration in which a current sensor is arranged in the U-phase and W-phase wirings of the three wirings connected from the inverter 3a to the motor 1 as the current detection unit 5a. Not limited. The two current sensors in the current detection unit 5a may be arranged in any two of the U phase, the V phase and the W phase. The current detection unit 5b can be configured in the same manner as the current detection unit 5a.

As the current sensor, an AC current transformer (Alternating Current Current Transformer: ACCT) is exemplified, but a DC current transformer (Direct Current Current Transformer: DCCT) or a shunt resistor may be used. When a shunt resistor is used, the shunt resistor is generally arranged on the negative side DC bus connecting the power source 2 and each of the inverters 3a and 3b, or on the negative side in each phase leg of the inverters 3a and 3b. To. Each detected value of the inverter current in the inverters 3a and 3b detected by the current detection units 5a and 5b is input to the control unit 4.

The control unit 4 calculates the voltage to be output to the motor 1 and generates a three-phase voltage command value based on the calculated voltage. When generating a three-phase voltage command value by calculation, well-known methods such as two-phase modulation, third-order harmonic superimposition modulation, and space vector modulation can be used. The control unit 4 generates a PWM signal for each of the inverters 3a and 3b based on the three-phase voltage command value and the bus voltage, and outputs the PWM signal to the inverters 3a and 3b. The bus voltage referred to here is equivalent to the DC voltage output from the power source 2.

Next, the switching mode of the motor drive device 100 according to the first embodiment and the switching operation of the inverters 3a and 3b performed according to the switching mode will be described. FIG. 4 is a time chart showing an example of a PWM signal which is a switching command when each of the inverters 3a and 3b in the first embodiment is driven in the first switching mode. The first switching mode is a mode in which the switching operation is performed by aligning the on and off timings of the switching elements between the in-phases of the inverters 3a and 3b.

The upper part of FIG. 4 shows a waveform of voltage command values Vu *, Vv *, Vw * which is a three-phase sine wave, and a carrier signal having an amplitude Vdc / 2 which changes in a triangular wave shape. The voltage command values Vu *, Vv *, and Vw * may be waveforms other than the three-phase sine wave, and the carrier signal may be a sawtooth wave instead of the triangular wave. Further, in the middle and lower portions of FIG. 4, the PWM signals UP1, UN1, VP1, VN1, WP1, WN1 for the inverter 3a in the first switching mode and the PWM signals UP2, UN2 for the inverter 3b in the first switching mode are shown. VP2, VN2, WP2, WN2 are shown alternately for each phase. In FIG. 4 and FIG. 5 described later, the identification symbol of the PWM signal is the same as the code of each switching element of the inverters 3a and 3b.

The control unit 4 compares the voltage command values Vu *, Vv *, and Vw * with the carrier signal as the reference signal, and generates PWM signals UP1, UN1, VP1, VN1, WP1, WN1 based on the mutual magnitude relationship. ..

In FIG. 4, when the U-phase voltage command value Vu * is larger than the carrier signal, the PWM signal UP1 is shown at a high level as the voltage for turning on the switching element UP1, and the PWM signal UN1 is the voltage for turning off the switching element UN1. Shown at low level as. This method is called a complementary PWM method. On the contrary, when the U-phase voltage command value Vu * is smaller than the carrier signal, the PWM signal UP1 is a voltage that turns off the switching element UP1, and the PWM signal UN1 is a voltage that turns on the switching element UN1. May be good.

The same applies to the other phases, V phase and W phase. The PWM signals VP1 and VN1 are determined by comparing the V-phase voltage command value Vv * with the carrier signal, and the PWM signals WP1 and WN1 are determined by comparing the W-phase voltage command value Vw * with the carrier signal.

In the case of the complementary PWM method, the PWM signal UP1 and the PWM signal UN1, the PWM signal VP1 and the PWM signal VN1, and the PWM signal WP1 and the PWM signal WN1 have opposite polar relationships with each other. By combining this switching pattern, the on / off switching operation of the switching element of the inverter 3a can be appropriately controlled, and a desired voltage can be output from the inverter 3a to the motor 1.

However, when two in-phase switching elements, for example, the PWM signal UP1 and the PWM signal UN1 are turned on at the same time, a large short-circuit current flows in the power source 2. Therefore, in practice, a short-circuit prevention time called a dead time is provided in the PWM signal so that two switching elements having the same phase do not turn on at the same time in consideration of a delay in the switching operation. In addition, about FIG. 4 and FIG. 5 described later, the description does not include the short circuit prevention time.

The PWM signals UP2, UN2, VP2, VN2, WP2, WN2 of the inverter 3b are also generated in the same manner as the PWM signals UP1, UN1, VP1, VN1, WP1, WN1 of the inverter 3a.

Comparing each PWM signal of the inverter 3a and each PWM signal of the inverter 3b for each phase, the timing of turning on and off each switching element is the same. That is, in the first switching mode, the switching operation of the switching element is aligned with the in-phase of the inverters 3a and 3b.

By aligning the on and off timings of the switching elements with the in-phase of the inverters 3a and 3b, it is possible to maintain the equilibrium of the output voltage output from the inverters 3a and 3b. As a result, if there is no difference or change in the environment in which the inverters 3a and 3b are arranged, the desired inverter output can be obtained.

Next, the switching operation of the inverters 3a and 3b in the second switching mode will be described. The second switching mode is a mode in which the switching operation is performed with the on and off timings of the switching elements being different between the in-phases of the inverters 3a and 3b.

When the pulse widths of the PWM signals in the inverters 3a and 3b are the same, the fundamental wave components of the output voltages of the inverters 3a and 3b are kept the same. Therefore, if there is no difference or change in the environment in which the inverters 3a and 3b are arranged, a desired inverter output can be obtained. On the other hand, when there is a difference or change in the environment in which the inverters 3a, 3b are arranged, the difference or change in these environments becomes large with the passage of time, and the wiring temperature between the inverters 3a, 3b and the motor 1 changes. It appears as a variation in wiring resistance or a change in the state of the motor. Further, a difference or change in the environment in which the inverters 3a and 3b are arranged fluctuates the cooling capacity of the inverters 3a and 3b, and appears as a temperature variation of the switching element in the inverters 3a and 3b. Therefore, there is a possibility that the desired inverter output cannot be obtained only by the operation of the first switching mode. Therefore, a second switching mode is prepared.

FIG. 5 is a time chart showing an example of a PWM signal which is a switching command when each of the inverters 3a and 3b in the first embodiment is driven in the second switching mode.

Similar to FIG. 4, the upper part of FIG. 5 shows the waveforms of the voltage command values Vu *, Vv *, Vw * and the carrier signal having the amplitude Vdc / 2. In the lower middle part of FIG. 5, the PWM signals UP1, UN1, VP1, VN1, WP1, WN1 for the inverter 3a in the second switching mode and the PWM signals UP2, UN2, VP2 for the inverter 3b in the second switching mode are shown. VN2, WP2, and WN2 are shown alternately for each phase. In FIG. 5, the waveforms of the PWM signals UP1, UN1, VP1, VN1, WP1, WN1 and the timing at which the polarity changes are the same as in FIG.

As described above, the second switching mode is a mode in which the switching operation is performed with the on and off timings of the switching elements different between the in-phases of the inverters 3a and 3b. In the example of FIG. 5, the on / off timing of each switching element in the inverter 3b is controlled to be delayed by the time difference Te with respect to the on / off timing of each switching element in the inverter 3a. The time difference Te is the amount of shift in the timing of turning on or off of the switching element for each phase in the inverters 3a and 3b. When controlled in this way, the variation in wiring resistance due to the change in the wiring temperature between the inverters 3a and 3b and the motor 1 and the temperature variation of the switching element in the inverters 3a and 3b act in a direction of becoming smaller. This makes it possible to suppress fluctuations in the inverter output due to differences or changes in the environment in which the inverters 3a and 3b are arranged.

If the influence of the variation in the wiring resistance due to the change in the wiring temperature between the inverters 3a and 3b and the motor 1 and the temperature variation of the switching element in the inverters 3a and 3b is small, the PWM signal in the inverters 3a and 3b It is preferable that the pulse widths are the same. By controlling in this way, it is possible to suppress fluctuations in the inverter output while keeping the fundamental wave components of the output voltages of the inverters 3a and 3b the same.

On the other hand, when the influence of the above-mentioned variation in wiring resistance and the variation in temperature of the switching element becomes large instantaneously or suddenly, the pulse widths of the PWM signals in the inverters 3a and 3b are made different. May be good. By controlling in this way, it is possible to quickly perform control to eliminate the imbalance of the inverter current between the inverters 3a and 3b and restore the equilibrium.

The method of providing a time difference Te for each phase has been described above as a method of controlling the on / off timing of the switching element in the inverter 3b so as to be different when the same phases of the inverter 3a are compared. Not limited to. For example, voltage command values Vu *, Vv *, Vw * are individually generated for each of the inverters 3a, 3b, and phase differences are provided for the voltage command values Vu *, Vv *, Vw * in each of the inverters 3a, 3b. You may. By comparing the voltage command values Vu *, Vv *, and Vw * with the phase difference with the same carrier signal, the intended PWM signal can be generated.

Alternatively, the voltage command values Vu *, Vv *, Vw * may be common among the inverters 3a and 3b, and the carrier signal may be different among the inverters 3a and 3b.

Alternatively, for each PWM signal generated by the same method as in the first switching mode, the on and off timings are individually corrected for the pair of switching elements for each phase in the inverters 3a and 3b. May be good.

Further, in the explanation so far, the switching pattern of the inverter 3b is adjusted based on the inverter 3a, but the present invention is not limited to this. On the contrary, the switching pattern of the inverter 3a may be adjusted with reference to the inverter 3b.

Next, the method of selecting the switching mode will be described with reference to FIG. FIG. 6 is a flowchart for explaining the method of selecting the switching mode in the first embodiment. In the first embodiment, the case where the mode selection information is the inverter current detected by the current detection units 5a and 5b will be described. As described above, the inverter current is the output current output from the respective inverters 3a and 3b to the motor 1.

First, the control unit 4 controls the inverters 3a and 3b to drive the motor 1 in the first switching mode (step S11). In the motor 1 and the inverters 3a and 3b, if the variation in wiring resistance, the variation in the temperature of the switching element, and the like are small, the output balance of the inverter current is maintained.

The control unit 4 acquires the detection value of the inverter current in the inverters 3a and 3b from the current detection units 5a and 5b (step S12). The control unit 4 calculates the difference current based on the detected value of the inverter current (step S13). The difference current may be information that shows the difference in the inverter current between the inverters 3a and 3b, and the physical quantity of the information does not have to be the current.

The control unit 4 compares the difference current with a predetermined allowable value (step S14). If the difference current is equal to or less than the allowable value (steps S14 and No), the process returns to step S11 and the above process is repeated. On the other hand, when the difference current exceeds the allowable value (step S14, Yes), the control unit 4 controls the inverters 3a and 3b to drive the motor 1 in the second switching mode (step S15).

As described above, the control unit 4 drives the motor 1 in the first switching mode when the difference current is equal to or less than the allowable value, and drives the motor 1 in the second switching mode when the difference current exceeds the allowable value. Drive. That is, the control unit 4 controls to switch the switching mode for driving the motor 1 between the first switching mode and the second switching mode based on the difference current.

Further, when the control unit 4 is driven in the second switching mode, if the difference current returns to the allowable value or less, the control unit 4 switches the switching mode from the second switching mode to the first switching mode. For example, when the load 6 is switched from the high load operation to the medium or light load operation, the inverter current and the motor current continue to be small, and the temperatures of the inverters 3a, 3b and the motor 1 are less likely to rise. Alternatively, since the temperature of the inverters 3a and 3b and the ambient temperature are lowered by the external cooling mechanism or natural cooling, the variation in the wiring resistance and the temperature variation in the switching element are gradually reduced. In such a state, the output equilibrium of the inverter current is maintained even if the motor 1 is driven in the first switching mode.

In the above step S14, the case where the difference current and the allowable value are equal is determined as "No", but it may be determined as "Yes". That is, the control unit 4 may determine the case where the difference current and the permissible value are equal to each other by either "Yes" or "No". In any case, the control unit 4 drives the motor 1 in the first switching mode if the difference current is within the allowable value range, and switches the motor 1 to the second switching if the difference current is outside the allowable value range. Drive in mode.

Further, in step S14 described above, the comparison target of the allowable values is the difference current, but the comparison is not limited to this. Instead of the difference current, the current ratio, which is the ratio between the detection value of the current detection unit 5a and the detection value of the current detection unit 5b, may be used.

Further, in the above step S15, the motor 1 is driven in the second switching mode. In this case, a time difference Te is set for each phase between the timing of turning on or off the switching element in the inverter 3b and the timing of turning on or off the switching element in the inverter 3a. The time difference Te may be a fixed value or a variable value according to the difference current. When the value is variable, the relationship between the difference current and the time difference Te may be obtained in advance, and the time difference Te may be changed according to the magnitude of the difference current. This control can be realized by configuring a control system inside the control unit 4 in which the difference current is the control amount and the time difference Te for each phase is the operation amount.

Further, the positive and negative values of the time difference Te, that is, the direction of the time difference Te shift may be controlled as follows. Here, the detected value of the inverter current detected by the current detection unit 5a is referred to as "current of the inverter 3a", and the detected value of the inverter current detected by the current detection unit 5b is referred to as "current of the inverter 3b". .. Further, the voltage applied by the inverter 3a to the motor 1 is referred to as "output voltage of the inverter 3c", and the voltage applied by the inverter 3b to the motor 1 is referred to as "output voltage of the inverter 3b".

For example, when the value of "current of inverter 3a-current of inverter 3b" is larger than a predetermined positive allowable value, the output voltage of the inverter 3a becomes larger than the output voltage of the inverter 3b. Therefore, in this case, the direction and magnitude of the shift of the time difference Te are controlled so that the output voltage of the inverter 3a becomes relatively small with respect to the output voltage of the inverter 3b. As long as the output voltage of the inverter 3a is relatively small with respect to the output voltage of the inverter 3b, the direction of the shift of the time difference Te, that is, the positive or negative of the value of the time difference Te does not matter.

Further, when the value of "current of inverter 3a-current of inverter 3b" is smaller than a predetermined negative allowable value, the output voltage of the inverter 3a becomes smaller than the output voltage of the inverter 3b. Therefore, in this case, the direction and magnitude of the shift of the time difference Te are controlled so that the output voltage of the inverter 3a becomes relatively large with respect to the output voltage of the inverter 3b. As long as the output voltage of the inverter 3a is relatively large with respect to the output voltage of the inverter 3b, the direction of the shift of the time difference Te, that is, the positive or negative of the value of the time difference Te does not matter.

The value of the time difference Te is generally on the order of several hundred [ns] to several [μs] for the purpose of eliminating the imbalance of the inverter current caused by the variation of the wiring resistance, the temperature variation of the switching element, and the like. Become. If the value of the time difference Te is made larger than this, it may affect the voltage that should be output to the motor 1, so it is wise to avoid it.

When the absolute value of "current of inverter 3a-current of inverter 3b" is large, the pulse width of the PWM signal may be controlled to be different between the inverter 3a and the inverter 3b as described above. If this control is used in combination, the time for eliminating the imbalance between the inverters 3a and 3b can be shortened.

The difference current generated between the inverters 3a and 3b leads to an increase in the inverter loss and the motor loss. Further, since this difference current is superimposed on the current required by the motor 1 and flows to each inverter, there is a possibility that an overcurrent may occur due to the instantaneous current superposition.

Therefore, by selecting or switching the switching mode using the difference current as the mode selection information, in addition to the above-mentioned effects, the effect of suppressing the inverter loss and the motor loss can be obtained. Further, since the generation of overcurrent can be suppressed by the control based on the difference current, the probability that the switching element is damaged can be reduced. Furthermore, it is possible to reduce the element rating margin for reducing the probability that the switching element will be damaged.

Note that the above description is based on the premise that the motor 1 is driven by using both the inverters 3a and 3b in the first switching mode, but the present invention is not limited to this. In the region where the output of the motor 1 is small, the operation of one of the inverters 3a and 3b may be stopped and the motor 1 may be driven by the remaining one inverter. This point is the same in the following embodiments.

Further, in the above, the number of inverters connected in parallel to the same motor 1 is 2, but it is not limited to this. The number of inverters may be 3 or more. When the number of inverters is 3 or more, the difference between the maximum value and the minimum value of the inverter current may be calculated and the calculated value may be used as the difference current in the above flowchart. In this case, the time difference Te may be set and driven only for the inverter having the maximum inverter current, or the time difference Te may be set and driven for the inverter other than the inverter having the minimum inverter current. Further, it may be driven by a method other than these.

As described above, the motor drive device according to the first embodiment has the first and second switching modes selected based on the inverter current which is the mode selection information when the motor is driven by a plurality of inverters. Have. In the first switching mode, the switching operation of each inverter is performed by aligning the on and off timings of the switching elements in the same phase of each inverter among the plurality of inverters. In the second switching mode, the switching operation of each inverter is performed by setting the on / off timing of the switching element in the same phase of each inverter to be different among the plurality of inverters. The motor drive device drives the motor in the second switching mode when the difference current of the inverter current between the respective inverters exceeds the allowable value. This makes it possible to suppress fluctuations in the inverter output due to differences or changes in the environment in which each inverter is arranged.

In the above control, the inverter current, which is the mode selection information, can be realized only by the current detector that detects the inverter current of each inverter, and the current detector that detects the motor current flowing in each phase of the motor is unnecessary. Therefore, according to the motor drive device according to the first embodiment, the effect that the number of current detectors can be reduced can be obtained.

Next, the hardware configuration for realizing the function of the control unit 4 in the first embodiment will be described with reference to the drawings of FIGS. 7 and 8. FIG. 7 is a block diagram showing an example of a hardware configuration that realizes the function of the control unit 4 in the first embodiment. FIG. 8 is a block diagram showing another example of the hardware configuration that realizes the function of the control unit 4 in the first embodiment.

When a part or all of the functions of the control unit 4 in the first embodiment are realized, as shown in FIG. 7, a processor 300 that performs an operation, a memory 302 that stores a program read by the processor 300, And the interface 304 for inputting / outputting signals can be included.

The processor 300 may be an arithmetic unit such as an arithmetic unit, a microprocessor, a microcomputer, a CPU (Central Processing Unit), or a DSP (Digital Signal Processor). Further, the memory 302 includes a non-volatile or volatile semiconductor memory such as a RAM (Radom Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Project ROM), or an EEPROM (registered trademark) (Electrically EPROM). Examples thereof include magnetic discs, flexible discs, optical discs, compact discs, mini discs, and DVDs (Digital Versaille Disc).

The memory 302 stores a program that executes the function of the control unit 4 in the first embodiment. The processor 300 sends and receives necessary information via the interface 304, the processor 300 executes a program stored in the memory 302, and the processor 300 refers to a table stored in the memory 302 to perform the above-mentioned processing. It can be carried out. The calculation result by the processor 300 can be stored in the memory 302.

Further, when a part of the function of the control unit 4 in the first embodiment is realized, the processing circuit 303 shown in FIG. 8 can also be used. The processing circuit 303 corresponds to a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. The information input to the processing circuit 303 and the information output from the processing circuit 303 can be obtained via the interface 304.

Note that some processing in the control unit 4 may be performed by the processing circuit 303, and processing not performed by the processing circuit 303 may be performed by the processor 300 and the memory 302.

Embodiment 2.
In the first embodiment, the case where the inverter current detected by the current detection unit is the motor selection information has been described. In the second embodiment, the case where the temperature information detected by the temperature detector is the motor selection information will be described.

FIG. 9 is a circuit diagram showing the configuration of the motor drive device 100a according to the second embodiment. In the motor drive device 100a according to the second embodiment, the control unit 4 is replaced with the control unit 4a, and the inverters 3a and 3b are replaced with the inverters 3c and 3d, as compared with the configuration of FIG. Further, the inverter 3c is provided with a temperature detector 7a, and the inverter 3d is provided with a temperature detector 7b. Other configurations are the same as or equivalent to those in FIG. 1, and the same or equivalent components are indicated by the same reference numerals, and duplicate explanations are omitted. In the following, the temperature detectors 7a and 7b may be collectively referred to as "first temperature detector".

The temperature detector 7a detects the temperature of the inverter 3c, and the temperature detector 7b detects the temperature of the inverter 3d. The temperature of the inverters 3c and 3d may be the internal temperature of each or the external ambient temperature of each. Specifically, the temperature detectors 7a and 7b may be, for example, a temperature sensor built in a power module composed of six switching elements in the respective inverters 3c and 3d. Alternatively, the temperature detectors 7a and 7b may be configured to convert the temperature into an electric signal by attaching a temperature sensor to each of the inverters 3c and 3d. An example of a temperature sensor is a thermistor or thermocouple.

Next, the method of selecting the switching mode in the second embodiment will be described with reference to FIG. FIG. 10 is a flowchart for explaining the method of selecting the switching mode in the second embodiment. In the second embodiment, the case where the mode selection information is the temperature of the inverters 3c and 3d detected by the temperature detectors 7a and 7b will be described.

First, the control unit 4a controls the inverters 3c and 3d to drive the motor 1 in the first switching mode (step S21). If the temperature difference between the inverters 3c and 3d is small in the motor 1 and the inverters 3c and 3d, the variation in wiring resistance and the temperature variation in the switching element are also small, and the output balance of the inverter current is maintained.

The control unit 4 acquires the temperature detection values of the inverters 3c and 3d from the temperature detectors 7a and 7b (step S22). The control unit 4 calculates the temperature difference based on the detected value of the temperature (step S23).

The control unit 4a compares the temperature difference with a predetermined allowable value (step S24). If the temperature difference is equal to or less than the allowable value (steps S24 and No), the process returns to step S21 and the above processing is repeated. On the other hand, when the temperature difference exceeds the permissible value (step S24, Yes), the control unit 4a controls the inverters 3c and 3d to drive the motor 1 in the second switching mode (step S25).

As described above, the control unit 4a drives the motor 1 in the first switching mode when the temperature difference is equal to or less than the allowable value, and drives the motor 1 in the second switching mode when the temperature difference exceeds the allowable value. Drive. That is, the control unit 4a controls to switch the switching mode for driving the motor 1 between the first switching mode and the second switching mode based on the temperature difference.

Further, when the control unit 4a is driven in the second switching mode, if the temperature difference returns to the allowable value or less, the control unit 4a switches the switching mode from the second switching mode to the first switching mode. For example, when the load 6 is switched from the high load operation to the medium or light load operation, the inverter current and the motor current continue to be small, and the temperatures of the inverters 3c, 3d and the motor 1 are less likely to rise. Alternatively, since the temperature of the inverters 3c and 3d and the ambient temperature are lowered by the external cooling mechanism or natural cooling, the variation in the wiring resistance and the temperature variation of the switching element are gradually reduced. In such a state, the output equilibrium of the inverter current is maintained even if the motor 1 is driven in the first switching mode.

In the above step S24, the case where the temperature difference and the permissible value are equal is determined as "No", but it may be determined as "Yes". That is, the control unit 4a may determine whether the temperature difference and the permissible value are equal to each other by either "Yes" or "No". In any case, the control unit 4a drives the motor 1 in the first switching mode if the temperature difference is within the allowable value range, and switches the motor 1 to the second switching mode if the temperature difference is out of the allowable value range. Drive in mode.

Further, in step S24 described above, the comparison target of the allowable values is the temperature difference, but the comparison is not limited to this. Instead of the temperature difference, a temperature ratio which is a ratio between the detection value of the temperature detector 7a and the detection value of the temperature detector 7b may be used.

Further, in the above step S25, the motor 1 is driven in the second switching mode. In this case, a time difference Te is set for each phase between the timing of turning on or off the switching element in the inverter 3d and the timing of turning on or off the switching element in the inverter 3c. The time difference Te may be a fixed value or a variable value according to the temperature difference. When the value is variable, the relationship between the temperature difference and the time difference Te may be obtained in advance, and the time difference Te may be changed according to the magnitude of the temperature difference. This control can be realized by configuring a control system inside the control unit 4a in which the temperature difference is used as the control amount and the time difference Te for each phase is used as the operation amount.

The positive and negative values of the time difference Te, that is, the direction of the time difference Te shift may be controlled or set in the same manner as in the first embodiment. Since the contents are duplicated, the explanation here is omitted.

The temperature difference between the inverters 3c and 3d leads to an increase in inverter loss and motor loss. Further, since this temperature difference is superimposed on the current required by the motor 1 and flows to each inverter, there is a possibility that an overcurrent may occur due to the instantaneous current superposition.

Therefore, by selecting or switching the switching mode using the temperature difference as the mode selection information, the effect that the inverter loss and the motor loss can be suppressed can be obtained. Further, since the generation of overcurrent can be suppressed by the control based on the temperature difference, the probability that the switching element is damaged can be reduced. Further, the element rating margin for reducing the probability of the switching element can be reduced.

As described above, the motor drive device according to the second embodiment includes a first temperature detector that detects the temperature of each of the plurality of inverters, and each temperature information detected by the first temperature detector. Is used as motor selection information. Then, when the temperature difference between the respective inverters exceeds the allowable value, the motor drive device drives the motor in the second switching mode. This makes it possible to suppress fluctuations in the inverter output due to differences or changes in the environment in which each inverter is arranged.

In the above, only the temperature information of each inverter is described as the mode selection information, but the difference current described in the first embodiment may be combined and used as the mode selection information. By doing so, more accurate inverter control and motor drive can be performed.

Embodiment 3.
In the second embodiment, the case where the temperature information detected by the first temperature detector is the motor selection information has been described. In the third embodiment, the case where the temperature information detected by another temperature detector is the motor selection information will be described.

FIG. 11 is a circuit diagram showing the configuration of the motor drive device 100b according to the third embodiment. In the motor drive device 100b according to the third embodiment, the control unit 4 is replaced with the control unit 4b as compared with the configuration of FIG. Further, a reactor 8a is provided between the inverter 3a and the motor 1, and a reactor 8b is provided between the inverter 3b and the motor 1. Further, the reactor 8a is provided with a temperature detector 7c, and the reactor 8b is provided with a temperature detector 7d. Other configurations are the same as or equivalent to those in FIG. 1, and the same or equivalent components are indicated by the same reference numerals, and duplicate explanations are omitted. In the following, the temperature detectors 7c and 7d may be collectively referred to as "second temperature detector".

Since the reactor has an inductance component, it has the effect of suppressing changes in current. Therefore, as shown in FIG. 11, inserting the reactors 8a and 8b has the effect of suppressing the difference current between the inverters 3a and 3b. On the other hand, since the reactor has a resistance component, it has a temperature dependence. Therefore, the resistance values of the reactors 8a and 8b change depending on the temperature, which causes variation. If the inverters 3a and 3b are driven in consideration of this temperature dependence, it becomes easier to obtain a desired inverter output. Therefore, in the third embodiment, the reactors 8a and 8b are provided with temperature detectors 7c and 7d.

Note that, in FIG. 11, a reactor 8a is provided between the inverter 3a and the motor 1, and a reactor 8b is provided between the inverter 3b and the motor 1, but the configuration is not limited to this. When the wiring cable connecting the inverters 3a and 3b and the motor 1 is long, the inductance component of the wiring cable itself can be used. Therefore, if the wiring cable is long, the wiring cable may be used instead. In this case, the temperature detectors 7c and 7d are provided on the wiring cable. The temperature detectors 7c and 7d may be the same as the temperature detectors 7a and 7b in the second embodiment.

Next, the method of selecting the switching mode in the third embodiment will be described with reference to FIG. FIG. 12 is a flowchart for explaining the method of selecting the switching mode in the third embodiment. In the third embodiment, the case where the mode selection information is the temperature of the reactors 8a and 8b detected by the temperature detectors 7c and 7d will be described.

First, the control unit 4b controls the inverters 3a and 3b to drive the motor 1 in the first switching mode (step S31). If the temperature difference between the reactors 8a and 8b is small in the motor 1 and the inverters 3a and 3b, the variation in wiring resistance and the temperature variation in the switching element are also small, and the output balance of the inverter current is maintained.

The control unit 4b acquires the temperature detection values of the reactors 8a and 8b from the temperature detectors 7c and 7d (step S32). The control unit 4b calculates the temperature difference between the reactors 8a and 8b based on the detected temperature value (step S33).

The control unit 4b compares the temperature difference with a predetermined allowable value (step S34). If the temperature difference is equal to or less than the allowable value (steps S34 and No), the process returns to step S31 and the above processing is repeated. On the other hand, when the temperature difference exceeds the permissible value (step S34, Yes), the control unit 4b controls the inverters 3a and 3b to drive the motor 1 in the second switching mode (step S35).

As described above, the control unit 4b drives the motor 1 in the first switching mode when the temperature difference is equal to or less than the allowable value, and drives the motor 1 in the second switching mode when the temperature difference exceeds the allowable value. Drive. That is, the control unit 4b controls to switch the switching mode for driving the motor 1 between the first switching mode and the second switching mode based on the temperature difference.

Further, when the control unit 4b is driven in the second switching mode, if the temperature difference returns to the allowable value or less, the control unit 4b switches the switching mode from the second switching mode to the first switching mode. For example, when the load 6 is switched from the high load operation to the medium or light load operation, the inverter current and the motor current continue to be small, and the temperature difference between the reactors 8a and 8b also becomes small. In such a state, the output equilibrium of the inverter current is maintained even if the motor 1 is driven in the first switching mode.

In the above step S34, the case where the temperature difference and the allowable value are equal is determined as "No", but it may be determined as "Yes". That is, the control unit 4b may determine whether the temperature difference and the permissible value are equal to each other by either "Yes" or "No". In any case, the control unit 4b drives the motor 1 in the first switching mode if the temperature difference is within the allowable value range, and switches the motor 1 to the second switching mode if the temperature difference is out of the allowable value range. Drive in mode.

Further, in step S34 above, the comparison target of the allowable values is the temperature difference, but the comparison is not limited to this. Instead of the temperature difference, a temperature ratio which is a ratio between the detection value of the temperature detector 7c and the detection value of the temperature detector 7d may be used.

Further, in the above step S35, the motor 1 is driven in the second switching mode. In this case, a time difference Te is set for each phase between the timing of turning on or off the switching element in the inverter 3b and the timing of turning on or off the switching element in the inverter 3a. The time difference Te may be a fixed value or a variable value according to the temperature difference. When the value is variable, the relationship between the temperature difference and the time difference Te may be obtained in advance, and the time difference Te may be changed according to the magnitude of the temperature difference. This control can be realized by configuring a control system inside the control unit 4b in which the temperature difference is used as the control amount and the time difference Te for each phase is used as the operation amount.

The positive and negative values of the time difference Te, that is, the direction of the time difference Te shift may be controlled or set in the same manner as in the first embodiment. Since the contents are duplicated, the explanation here is omitted.

The temperature difference between the reactors 8a and 8b is related to the temperature difference that occurs between the inverters 3a and 3b. If there is a temperature difference between the inverters 3a and 3b, the inverter loss and the motor loss will increase. Further, since this temperature difference is superimposed on the current required by the motor 1 and flows to the respective inverters 3a and 3b, there is a possibility that an overcurrent may occur due to the instantaneous current superposition.

Therefore, by selecting or switching the switching mode using the temperature difference between the reactors 8a and 8b as the mode selection information, the effect that the inverter loss and the motor loss can be suppressed can be obtained. Further, since the generation of overcurrent can be suppressed by the control based on the temperature difference, the probability that the switching element is damaged can be reduced. Further, the element rating margin for reducing the probability of the switching element can be reduced.

As described above, the motor drive device according to the third embodiment includes a second temperature detector that detects each temperature in the wiring cable or the reactor inserted in the wiring cable, and is the second temperature detector. Each detected temperature information is used as motor selection information. Then, the motor driving device drives the motor in the second switching mode when the temperature difference between the wiring cables or the reactor exceeds the allowable value. This makes it possible to suppress fluctuations in the inverter output due to differences or changes in the environment in which each inverter is arranged.

In the above, the temperature information between the wiring cables or the reactors is described as the mode selection information, but the difference current described in the first embodiment and the temperature information between the inverters described in the second embodiment are described. At least one of the temperature differences may be combined and used as mode selection information. By doing so, more accurate inverter control and motor drive can be performed.

Embodiment 4.
In the fourth embodiment, a case where the motor driven by the two inverters is a connection switching motor configured to switch the connection state and the connection state of the motor is the motor selection information will be described.

FIG. 13 is a circuit diagram showing the configuration of the motor drive device 100c according to the fourth embodiment. In the motor drive device 100c according to the fourth embodiment, the control unit 4 is replaced with the control unit 4c as compared with the configuration of FIG. Further, in FIG. 13, the motor 1 is replaced with the motor 1a. The motor 1a is a connection switching motor in which the end of the winding of each phase is pulled out to the outside of the motor 1a. Further, the motor drive device 100c is provided with a connection switching unit 9 for switching the connection state of the motor 1a. Other configurations are the same as or equivalent to those in FIG. 1, and the same or equivalent components are indicated by the same reference numerals, and duplicate explanations are omitted.

As shown in FIG. 13, the connection switching unit 9 includes switches 90u, 90v, 90w and switches 91u, 91v, 91w. These switches 90 and switch 91 are called electromagnetic contactors whose contacts are electromagnetically opened and closed. Examples of these include relays, contactors and the like. Further, the functions of the switch 90 and the switch 91 may be realized by a semiconductor switch. The switch 90 and the switch 91 are controlled to open / close or switch based on a command from the control unit 4c.

Each of the switch 91 has a function of switching between two circuits. This function can be configured with a c-contact relay. Of course, if each has a function of switching between two circuits, it may be configured by using something other than the c-contact relay.

When the switch 91 is a c-contact relay, each has three terminals, a common terminal COM, a normally open terminal NO, and a normally closed terminal NC. The common terminal COM is connected to the output end of the inverter 3b. The normally open terminal NO of the switch 91 is connected to the output end of the inverter 3a. The normally open terminal NO of the switch 91 is also connected to terminals UA, VA, and WA, which are first terminals from which one end of the winding of the motor 1a is pulled out. The normally closed terminal NC of the switch 91 is connected to terminals UB, VB, WB which are second terminals from which the other end of the winding of each phase of the motor 1a is pulled out. The normally closed terminal NC of the switch 91 is also connected to one terminal of the switch 90. The other terminal of the switch 90 is connected to the neutral point node 92 in order to configure each phase winding of the motor 1a in a Y-connected state. It should be noted that the normally closed terminal NC and the normally open terminal NO may be interchanged. Hereinafter, the description will be given based on the connection state of FIG.

In the configuration of FIG. 13, all the switches 90 are turned on, and the switch 91 is switched to the normally open terminal NO side. In this case, the output end side of the inverter 3a and the output end side of the inverter 3b are connected to the terminals UA, VA, WA of the motor 1a, and the terminals UB, VB, WB of the motor 1a are connected to the neutral point node 92. Will be done. That is, the terminals UA, VA, and WA of the motor 1a are connected to both output ends of the inverters 3a and 3b. This is a mode in which the motor 1a in the Y-connected state is driven by the two inverters 3a and 3b, that is, the same connection state as in the above-described embodiment. Hereinafter, this connection state is referred to as a "first connection state".

In the first connection state, a larger current than when driving the motor 1a in the Y connection state with one inverter, ideally twice the current, can be supplied to the motor 1a. Therefore, in the first connection state, the motor torque can be increased by the amount of the increased current. Therefore, the first connection state can contribute to high output in the low speed range, which does not require a particularly large motor voltage.

Also, all the switches 90 are turned off, and the switch 91 is switched to the normally closed terminal NC side. In this case, the terminals UA, VA, WA of the motor 1a are connected to the output end side of the inverter 3a, and the terminals UB, VB, WB of the motor 1a are connected to the output end side of the inverter 3b. This is a form in which the motor 1a of the open winding type is driven by the two inverters 3a and 3b. Hereinafter, this connection state is referred to as a "second connection state".

In the second connection state, a larger voltage than when driving the motor 1a in the Y connection state with one inverter, ideally twice the voltage, can be supplied to the motor 1a. Therefore, the second connection state can contribute to increasing the output in the high-speed range, which requires a particularly large motor voltage, as the voltage is increased.

By appropriately switching between the first connection state and the second connection state, the supply current to the motor 1a can be increased and the motor torque can be increased in the low speed range. Further, in the high speed range, the output of the motor 1a can be increased by increasing the voltage applied to the motor 1a. As a result, the operating range of the motor 1a can be expanded regardless of the speed band.

Next, a method of selecting either one of the first switching mode and the second switching mode based on the mode selection information will be described. In the fourth embodiment, the mode selection information is the connection state of the motor 1a.

First, a case of driving the motor 1a in the first connection state will be described. When driving the motor 1a in the first connection state by using the two inverters 3a and 3b, the first switching mode and the second switching mode should be appropriately selected as in the above-described embodiment. Just do it.

Next, a case of driving the motor 1a in the second connection state will be described. As described above, the first switching mode is a mode in which the switching operation is performed by aligning the on and off timings of the switching elements between the in-phases of the inverters 3a and 3b. Therefore, when driving the motor 1a in the second connection state, if the first switching mode is selected, the terminals of the same phase of the motor 1a, that is, the terminals UA and the terminal UB, the terminal VA and the terminal VB, and the terminals WA and terminal WB have the same potential. Therefore, the voltage applied to the motor 1a by the inverter 3a and the voltage applied to the motor 1a by the inverter 3b cancel each other out, and the combined voltage applied to the motor 1a becomes almost zero, so that the motor 1a cannot be driven. Therefore, when driving the motor 1a in the second connection state, it is necessary to drive the motor 1a only in the second switching mode.

Therefore, when the motor 1a is an open winding, if either the first switching mode or the second switching mode is selected in consideration of the connection state of the motor 1a, the motor 1a cannot be driven. Can be avoided.

As described above, according to the motor drive device according to the fourth embodiment, when the motor is an open winding motor in which the end of the winding of each phase is pulled out to the outside of the motor, the motor is connected. The state is set as mode selection information, and the first or second switching mode is selected based on the mode selection information. Thereby, when the connection state of the motor is the first connection state, the effects described in the first to third embodiments can be obtained. Further, when the connection state of the motor is the second connection state, the effect that the mode in which the motor cannot be driven can be avoided can be obtained.

Embodiment 5.
In the fifth embodiment, an example in which the motor drive devices 100 to 100c described in the first to fourth embodiments are applied to the air conditioner will be described. The motor drive devices 100 to 100c described in the first to fourth embodiments are motor drive devices for driving one motor with a plurality of inverters. Therefore, by applying any one of the motor drive devices 100 to 100c to the air conditioner, the capacity of the air conditioner can be increased, and an air conditioner having high cooling / heating capacity and low loss can be realized. Can be done.

FIG. 14 is a diagram showing a configuration example of the air conditioner 200 according to the fifth embodiment. The air conditioner 200 includes an outdoor unit 67, an indoor unit 68, and an air conditioning control unit 69. The outdoor unit 67 is connected to the power source 2. The outdoor unit 67 includes a motor drive device 100, a compressor 60, a four-way valve 62, a heat source side heat exchanger 63, and a heat source side expansion valve 64. The indoor unit 68 includes a load-side expansion valve 65 and a load-side heat exchanger 66. The compressor 60 includes a compression element 61 whose drive source is the motor 1. Although the motor drive device 100 is illustrated in FIG. 14, it may be replaced with any one of the motor drive devices 100a to 100c.

In the air conditioner 200, the compressor 60, the four-way valve 62, the heat source side heat exchanger 63, the heat source side expansion valve 64, the load side expansion valve 65, the load side heat exchanger 66, the four-way valve 62, and the compressor 60. A refrigerant circuit connected by a refrigerant pipe 70 is configured in this order. In the air conditioner 200, the refrigeration cycle is established by the flow of the refrigerant through the refrigerant circuit. The air conditioner 200 compresses the refrigerant in the refrigeration cycle by the compressor 60. Although not shown in FIG. 14, an accumulator for storing excess refrigerant may be provided on the suction side of the compressor 60. In controlling the refrigerant circuit, the air conditioning control unit 69 controls the four-way valve 62, the heat source side expansion valve 64, and the load side expansion valve 65. The refrigerating cycle configuration shown in FIG. 14 is an example, and may not necessarily be the same refrigerating cycle configuration.

Next, the operation of the air conditioner shown in FIG. 14 will be described by taking a cooling operation as an example. Although details of the heating operation are omitted, the heating operation can also be realized by switching the flow path in the four-way valve 62. During the cooling operation, the four-way valve 62 flows the refrigerant discharged from the compressor 60 toward the heat source side heat exchanger 63 and the refrigerant flowing out from the load side heat exchanger 66 toward the compressor 60. It is assumed that the road is being switched.

By driving the motor 1 with the motor drive device 100, the compression element 61 connected to the motor 1 compresses the refrigerant into a high-temperature and high-pressure refrigerant. The compressor 60 discharges a high-temperature and high-pressure refrigerant. The high-temperature and high-pressure refrigerant discharged from the compressor 60 flows into the heat source side heat exchanger 63 via the four-way valve 62, exchanges heat with the external air in the heat source side heat exchanger 63, and dissipates heat. The refrigerant flowing out of the heat source side heat exchanger 63 is expanded and depressurized by the heat source side expansion valve 64 to become a low-temperature low-pressure gas-liquid two-phase refrigerant. The low-temperature low-pressure gas-liquid two-phase refrigerant is expanded and depressurized by the load-side expansion valve 65, flows into the load-side heat exchanger 66, exchanges heat with the air in the air-conditioned space, and evaporates to a low temperature. It becomes a low-pressure refrigerant and flows out from the load side heat exchanger 66. The refrigerant flowing out of the load side heat exchanger 66 is sucked into the compressor 60 via the four-way valve 62 and compressed again. In the air conditioner 200, the above operation is repeated.

The cooling plate may be brought into contact with the power module, which is a component of the inverters 3a, 3b, mainly for the purpose of cooling the inverters 3a, 3b of the motor drive device 100. Further, the refrigerant pipe 70 may be brought into contact with the cooling plate so that the refrigerant flowing through the refrigerant pipe 70 absorbs heat generated by the inverters 3a and 3b. By doing so, it is possible to efficiently suppress the temperature rise of the inverters 3a and 3b.

In the air conditioner 200 shown in FIG. 14, the heat source side expansion valve 64 is provided in the outdoor unit 67, and the load side expansion valve 65 is provided in the indoor unit 68. This is the cooling capacity of the motor drive device 100. This is to enable the two expansion valves, the heat source side expansion valve 64 and the load side expansion valve 65, to be independently controlled. This configuration is suitable for finely controlling the refrigerant, and the refrigerant can be efficiently controlled. The configuration of FIG. 14 is an example, and it is not always necessary to include two expansion valves, and the expansion valve may be provided in either the indoor unit 68 or the outdoor unit 67.

In the fifth embodiment, an example in which the motor drive devices 100 to 100c according to the first to fourth embodiments are applied to the air conditioner 200 is shown, but the present invention is not limited thereto. The motor drive devices 100 to 100c according to the first to fourth embodiments can be applied to devices having a refrigerating cycle, such as an air conditioner 200, a heat pump device, and a refrigerating device. It can also be applied to products that are not equipped with a compressor, such as dryers, washing machines, and vacuum cleaners, which obtain driving force by the rotational force of the motor, and can also be applied to fan motors and the like.

As described above, according to the air conditioner according to the fifth embodiment, by applying the motor drive device according to the first to fourth embodiments, the capacity of the air conditioner can be increased and the air conditioning capacity is high. Moreover, the effect that an air conditioner with a small loss can be realized can be obtained.

The configuration shown in the above embodiments is an example, and can be combined with another known technique, can be combined with each other, and does not deviate from the gist. It is also possible to omit or change a part of the configuration.

1,1a motor, 2 power source, 3a, 3b, 3c, 3d inverter, 4,4a, 4b, 4c control unit, 5a, 5b current detector, 6 load, 7a, 7b, 7c, 7d temperature detector, 8a , 8b reactor, 9 connection switching part, 21a three-phase AC power supply, 21b single-phase AC power supply, 22a, 22b AC / DC converter, 60 compressor, 61 compression element, 62 four-way valve, 63 heat source side heat exchanger, 64 heat source Side expansion valve, 65 load side expansion valve, 66 load side heat exchanger, 67 outdoor unit, 68 indoor unit, 69 air conditioning control unit, 70 refrigerant piping, 90u, 90v, 90w switch, 91u, 91v, 91w switch, 92 Neutral point node, 100, 100a, 100b, 100c motor drive device, 200 air conditioner, 300 processor, 302 memory, 303 processing circuit, 304 interface.

Claims (10)

1. A motor drive device equipped with multiple inverters that convert a DC voltage supplied from a power source into a three-phase AC voltage and apply it to the same motor.
   When driving the motor with a plurality of the inverters
   A first switching mode in which the on / off timing of the switching element in the same phase of each of the inverters is aligned between the plurality of inverters to perform the switching operation of each of the inverters.
   A second switching mode in which the switching operation of each of the inverters is performed with the on / off timing of the switching element in the same phase of each of the inverters being different between the plurality of inverters.
   Have,
   A motor drive device that selects the first or second switching mode based on the mode selection information.
2. A current detection unit that detects the current flowing through each of the plurality of inverters is provided.
   The motor drive device according to claim 1, wherein the mode selection information is each current detection value detected by the current detection unit.
3. A first temperature detector for detecting the temperature of each of the plurality of inverters is provided.
   The motor drive device according to claim 1 or 2, wherein the mode selection information is the respective temperature information detected by the first temperature detector.
4. The plurality of inverters and the motor are connected via a wiring cable.
   Each of the wiring cables is provided with a second temperature detector that detects the temperature of each of the wiring cables.
   The motor drive device according to any one of claims 1 to 3, wherein the mode selection information is each temperature information detected by the second temperature detector.
5. The plurality of inverters and the motor are connected via a wiring cable, and a reactor is inserted into the wiring cable.
   Each of the reactors is equipped with a second temperature detector that detects the temperature of each of the reactors.
   The motor drive device according to any one of claims 1 to 3, wherein the mode selection information is each temperature information detected by the second temperature detector.
6. If the mode selection information is within the allowable value range, the motor is driven in the first switching mode.
   The motor driving device according to any one of claims 2 to 5, wherein if the mode selection information is out of the allowable range, the motor is driven in the second switching mode.
7. The motor is an open winding motor in which the end of the winding of each phase is pulled out to the outside of the motor.
   A connection switching unit for switching the connection state of the motor is provided.
   The motor drive device according to claim 1, wherein the mode selection information is a wiring state of the motor.
8. The plurality of the inverters consist of a first and a second inverter.
   The first terminal from which one end of the winding of each phase of the motor is pulled out is connected to the first inverter, and the first terminal is connected to the second terminal via the connection switching portion. A first connection state in which the second terminal is short-circuited by connecting to an inverter and operating the connection switching unit so that the other end of the winding of each phase of the motor is pulled out.
   A second connection state in which the connection switching unit is operated so that the connection with the first terminal is limited to the first inverter and the second terminal is connected to the second inverter.
   7. The motor drive device according to claim 7.
9. The motor drive device according to claim 8, wherein the motor is driven only in the second switching mode in the second connection state.
10. The motor drive device according to any one of claims 1 to 9,
    A compressor using the motor as a drive source and
    Equipped with
    An air conditioner in which the refrigerant in the refrigeration cycle is compressed by the compressor.

Images