WO2021166124A1

WO2021166124A1 - Electric motor drive device and air conditioner

Info

Publication number: WO2021166124A1
Application number: PCT/JP2020/006551
Authority: WO
Inventors: 裕卓 ▲徳▼田; 貴彦小林; 惇川島
Original assignee: 三菱電機株式会社
Priority date: 2020-02-19
Filing date: 2020-02-19
Publication date: 2021-08-26

Abstract

An electric motor drive device (150) has: a switching unit (60) provided with a plurality of mechanical relays (61, 62, 63) that switch the connection state of a stator winding of an electric motor (70) to a star connection or a delta connection; an inverter (50) that applies electric power to the electric motor (70); and a control unit (90) that controls the switching unit (60), the control unit (90) causing the switching unit (60) to stop the switching of the connection state when the cumulative number of switchings, indicating the number of times the connection state was switched by the switching unit (60), is greater than or equal to a switching life number, which is a number of switchings at which it can no longer be guaranteed that the electrical opening/closing operation of the mechanical relays (61, 62, 63) is correctly performed.

Description

Motor drive and air conditioner

The present disclosure relates to an electric motor drive device for driving an electric motor by switching the connection state of the stator winding between a star connection and a delta connection, and an air conditioner equipped with the electric motor drive device.

The air conditioner equipped with an electric motor for the compressor that compresses the refrigerant adjusts the cooling capacity and heating capacity according to the rotation speed of the electric motor. Therefore, it is desired that the electric motor used in the air conditioner has high efficiency in a wide rotation speed range. An air conditioner equipped with an electric motor for a compressor has air conditioning efficiency at both low load and high load by switching the connection state of the electric motor between star connection and delta connection with the electric motor drive device. Can be enhanced.

Generally, when switching the connection of a motor, a semiconductor switch, a mechanical relay or an electromagnetic contactor is used, but since the semiconductor switch may cause a short mode failure, a mechanical relay or an electromagnetic contactor should be used. There are many. In particular, mechanical relays are widely used in consumer products because inexpensive ones are widely used. Therefore, there is a need for control that suppresses the risk of failure such as contact welding of mechanical relays.

In Patent Document 1, in case the contact plate itself of the mechanical relay breaks down, all three relays connected to the stator winding of the compressor are controlled so that the connection state is the same. A technique for improving the reliability of compressor operation is disclosed.

International Publication No. 2019/021398

Mechanical relays may fail if they exceed the mechanical switching life or the electrical switching life due to the breaking current. However, in the technique described in Patent Document 1, when a relay fails, all three relays have the same connection state, and the relay failure itself is not suppressed.

The present disclosure has been made in view of the above, and an object of the present disclosure is to obtain an electric motor drive device that suppresses a failure of a mechanical relay that switches the connection state of the windings of the electric motor.

In order to solve the above-mentioned problems and achieve the object, the motor drive device according to the present disclosure is a plurality of mechanical relays that switch the connection state of the stator windings of the motor to either star connection or delta connection. It has a switching unit provided with the above, an inverter for applying driving power to the motor, and a control unit for controlling the switching unit. In the control unit, the cumulative number of switching times, which indicates the number of times the connection state has been switched by the switching unit, is equal to or greater than the number of switching life times, which is the number of times that the electrical opening / closing operation of the mechanical relay is not guaranteed to be performed normally. Then, stop the switching of the connection state at the switching part.

The motor drive device according to the present disclosure has the effect of suppressing the failure of the mechanical relay that switches the connection state of the windings of the motor.

The figure which shows the state which the electric motor drive device which concerns on Embodiment 1 drive an electric motor by a star connection. The figure which shows the state which the electric motor drive device which concerns on Embodiment 1 drive an electric motor by a delta connection. A flowchart showing a flow of switching control of a mechanical relay based on the cumulative number of switchings of the motor driving device according to the first embodiment. The figure which shows the state which the electric motor drive device which concerns on Embodiment 2 drive an electric motor by a star connection. A flowchart showing a flow of switching control using the cumulative elapsed time of the motor drive device according to the second embodiment. The figure which shows the state which the electric motor drive device which concerns on Embodiment 3 drive an electric motor by a star connection. A flowchart showing the flow of switching control using the measured temperature of the motor drive device according to the third embodiment. The figure which shows the state which the electric motor drive device which concerns on Embodiment 4 drive an electric motor by a star connection. A flowchart showing the flow of switching control using the current detection value of the motor drive device according to the fourth embodiment. The figure which shows the structure of the air conditioner which concerns on Embodiment 5. The figure which shows the structure which realized the function of the control part of the motor drive device which concerns on one of Embodiment 1 to Embodiment 4 by hardware. The figure which shows the structure which realized the control part of the motor drive device which concerns on one of Embodiment 1 to Embodiment 4 by software.

The motor drive device and the air conditioner according to the embodiment will be described in detail below based on the drawings. It should be noted that this embodiment does not limit this disclosure.

Embodiment 1.
FIG. 1 is a diagram showing a state in which the motor drive device according to the first embodiment drives the motor with a star connection. FIG. 2 is a diagram showing a state in which the motor drive device according to the first embodiment drives the motor with a delta connection. The electric motor drive device 150 according to the first embodiment includes a reactor 20 that suppresses harmonics contained in an AC voltage supplied from an AC power supply 10, a rectifying unit 30 that rectifies an AC voltage in which harmonics are suppressed, and a rectifier. It has a capacitor 40 that smoothes the DC voltage output by the unit 30. Further, the motor drive device 150 includes an inverter 50 that converts a DC voltage into a three-phase AC voltage by a switching operation, a switching unit 60 that switches the connection state of the motor 70 to a star connection or a delta connection, and an inverter 50 and a switching unit 60. A control unit 90 for controlling is provided. The control unit 90 controls the inverter 50 by sending an inverter drive signal to the inverter 50. Further, the control unit 90 sends a switching signal to the switching unit 60 to control the switching unit 60. A storage unit 100 that stores information used for controlling the inverter 50 and the switching unit 60 is connected to the control unit 90. The number of storage units 100 connected to the control unit 90 may be one or a plurality. Information used for controlling the inverter 50 and the switching unit 60 may be stored in the storage unit 91 included in the control unit 90. Further, the information used for controlling the inverter 50 and the switching unit 60 may be stored separately in the storage unit 91 and the storage unit 100.

The rectifying unit 30 has rectifying

elements

31, 32, 33, 34. The inverter 50 has switching

elements

51, 52, 53, 54, 55, 56, each of which has a rectifying element connected in parallel. The inverter 50 converts a DC voltage into an AC voltage by the switching operation of the

switching elements

51, 52, 53, 54, 55, 56. The switching unit 60 has

mechanical relays

61, 62, 63. The control unit 90 applies a voltage to the motor 70 to drive the motor 70 by controlling the inverter 50 and the switching unit 60 according to the target value of the voltage or current stored in the storage unit 91.

The motor drive device 150 has a detection unit 80 including a voltage detection unit 81 that detects the voltage of the inverter 50 and a current detection unit 82 that detects the current of the inverter 50. The control unit 90 controls the switching unit 60 based on at least one of the voltage and the current detected by the detection unit 80.

The motor drive device 150 has a storage unit 100 that stores the cumulative number of times of switching, the number of times of switching life, the number of times of switching upper limit, and the switching permission flag used for determining whether or not switching is possible. The cumulative number of times of switching is the total number of times of transmission indicating how many times the switching signal is transmitted for contact switching of the

mechanical relays

61, 62, 63. The cumulative number of switchings is incremented by the control unit 90 each time the

mechanical relays

61, 62, and 63 are switched. The number of switching life is the number of switchings from which it is no longer guaranteed that the

mechanical relays

61, 62, 63 are normally opened and closed. When the cumulative number of switchings exceeds the number of switching lifes, the mechanical relay 61, There is a possibility that 62 and 63 will be damaged and the opening / closing operation will not be performed normally. The upper limit of switching indicates the worst design value assumed in product design. That is, the upper limit of switching needs to be less than the number of switching lifespans. It is desirable that the cumulative number of switchings is less than the number of switching lifespans and less than or equal to the upper limit of switchings.

The initial value of the switching permission flag is "valid". When the switching permission flag is "valid", the control unit 90 determines whether or not switching is possible. On the other hand, when the switching permission flag is "invalid", the control unit 90 continues the steady operation without determining whether or not switching is possible.

FIG. 3 is a flowchart showing the flow of switching control of the mechanical relay based on the cumulative number of switchings of the motor drive device according to the first embodiment. After the start of steady operation, when the load strength of the motor 70 changes and it becomes necessary to switch the connection state of the stator windings of the motor 70, the control unit 90 performs the process of FIG. In step S11, the control unit 90 reads out the number of switching lifes, the number of switching upper limits, and the cumulative number of switchings stored in the storage unit 100. In step S12, the control unit 90 acquires the switching permission flag stored in advance in the storage unit 100, and determines whether or not the switching permission flag is “valid”.

If the switching permission flag is "invalid", the result is No in step S12, and the process ends. When the switching permission flag is "valid", Yes is set in step S12, and the process proceeds to step S13. In step S13, the control unit 90 determines whether or not the cumulative number of switchings is less than the number of switching lifespans and equal to or less than the upper limit of switchings. If the cumulative number of switching times is equal to or greater than the number of switching lifespans, or if the cumulative number of switchings exceeds the upper limit of switchings, the result is No in step S13, and the process proceeds to step S16. If the cumulative number of switchings is less than the number of switching lifespans and equal to or less than the upper limit of switchings, the result is Yes in step S13, and the process proceeds to step S14.

In step S14, the control unit 90 sends a command to the switching unit 60 to switch the

mechanical relays

61, 62, 63. In step S15, the control unit 90 determines whether or not the switching of the

mechanical relays

61, 62, 63 is successful. If the switching of the

mechanical relays

61, 62, and 63 is successful, the result is Yes in step S15, and the process ends. If the switching of the

mechanical relays

61, 62, 63 is not successful, the result is No in step S15, and the process of step S15 is repeated until the switching of the

mechanical relays

61, 62, 63 is completed.

In step S16, the control unit 90 determines whether or not the cumulative number of switching times is equal to or greater than the number of switching lifespans. If the cumulative number of switching times is equal to or greater than the number of switching lifespans, the result is Yes in step S16, and the process proceeds to step S17. If the cumulative number of switching times is less than the number of switching life times, No in step S16, and the process ends.

In step S17, the control unit 90 sets the switching permission flag to "invalid".

In the motor drive device 150 according to the first embodiment, when the cumulative number of switching times is equal to or greater than the number of switching life times, the control unit 90 invalidates the switching permission flag, and thereafter, the

mechanical relays

61, 62, 63 are switched. Continue steady operation without. Since the motor drive device 150 according to the first embodiment suppresses the number of switchings of the

mechanical relays

61, 62, 63 by the cumulative number of switchings, it is possible to prevent the

mechanical relays

61, 62, 63 from failing. ..

The initial value of the switching permission flag may be "invalid". Further, it may be determined whether the switching permission flag is "valid" or "invalid" after the switching permission flag is set.

Further, at least one storage location of the cumulative number of times of switching, the number of times of switching life, the number of times of switching upper limit, and the switching permission flag may be the storage unit 91 in the control unit 90.

The storage unit 100 does not have to be in the motor drive device 150 as long as it is connected to the control unit 90. For example, in the case of an air conditioner, a product is produced by a one-to-one combination of an indoor unit and an outdoor unit, but when the outdoor unit has an electric motor drive device 150, even if the storage unit 100 is in the indoor unit. good.

Needless to say, the number of times of switching life and the number of times of switching upper limit may be set with a margin. In the flowchart shown in FIG. 3, since it is determined whether or not the

mechanical relays

61, 62, 63 can be switched before switching, the cumulative number of switching times is not normally less than the number of switching lifespans, but cumulative switching is caused by a disturbance factor. It is desirable to set the number of switching lifespans and the maximum number of switchings to be small in case the number of times is counted incorrectly.

In general, when the motor drive device is used beyond the product life or requires more switching times than expected at the time of design, the electric switching life of the mechanical relay is exceeded, and the mechanical type The relay itself may break down. If the contacts of the mechanical relay are welded due to a failure, the motor drive may fail. Therefore, the electric motor drive device 150 according to the first embodiment determines whether or not the

mechanical relays

61, 62, 63 can be switched by using the cumulative number of times the

mechanical relays

61, 62, 63 are switched, thereby determining the mechanical relay 61. , 62, 63 electrical contact switching is suppressed, and failure of

mechanical relays

61, 62, 63 is suppressed. Further, in the motor drive device 150 according to the first embodiment, since it is not necessary to switch all the

mechanical relays

61, 62, 63 at the same time, overcurrent and overvoltage are generated by switching the

mechanical relays

61, 62, 63 at the same time. Can be prevented. Therefore, the motor drive device 150 according to the first embodiment does not need to increase the component ratings of the

mechanical relays

61, 62, 63 or add elements or circuits for noise suppression, and can reduce the component cost. ..

Embodiment 2.
FIG. 4 is a diagram showing a state in which the motor drive device according to the second embodiment drives the motor with a star connection. The difference from the motor drive device 150 according to the first embodiment is that it has a clock unit 140. The clock unit 140 counts the elapsed time from the first startup. The control unit 90 stores the cumulative elapsed time acquired from the clock unit 140 in the storage unit 91. Therefore, the control unit 90 can acquire the cumulative elapsed time from the storage unit 91 at an arbitrary timing. Further, the storage unit 100 stores in advance the design upper limit time estimated from the product life assumed in the design.

FIG. 5 is a flowchart showing the flow of switching control using the cumulative elapsed time of the motor drive device according to the second embodiment. After the start of steady operation, when the load strength of the motor 70 changes and it becomes necessary to switch the connection state of the stator windings of the motor 70, the control unit 90 adds the processing shown in FIG. 3 to the process shown in FIG. Perform processing. In step S21, the control unit 90 reads out the design upper limit time and the cumulative elapsed time stored in the storage unit 100. In step S22, the control unit 90 acquires the switching permission flag stored in advance in the storage unit 100, and determines whether or not the switching permission flag is “valid”.

If the switching permission flag is "invalid", the result is No in step S22, and the process ends. When the switching permission flag is "valid", Yes is set in step S22, and the process proceeds to step S23. In step S23, the control unit 90 determines whether or not the cumulative elapsed time is less than the design upper limit time. If the cumulative elapsed time is equal to or longer than the design upper limit time, the result is No in step S23, and the process proceeds to step S26. If the cumulative elapsed time is less than the design upper limit time, the result is Yes in step S23, and the process proceeds to step S24.

The processing of steps S24 and S25 is the same as the processing of steps S14 and S15 shown in FIG.

In step S26, the control unit 90 sets the switching permission flag to "invalid".

Since the motor drive device according to the second embodiment sets the switching permission flag to "invalid" when the cumulative elapsed time is equal to or longer than the design upper limit time, the switching permission flag is "invalid" in step S22 at the next processing. By determining that, it is possible to continue the steady operation by omitting the determination of whether or not the cumulative elapsed time is less than the design upper limit time.

The motor drive device 150 according to the second embodiment determines whether or not the cumulative elapsed time is less than the design upper limit time, and if the cumulative elapsed time is equal to or more than the design upper limit time, the

mechanical relays

61, 62, 63 are switched. Continue steady operation without performing. That is, since the motor drive device 150 according to the second embodiment suppresses the number of times the

mechanical relays

61, 62, 63 are switched depending on the cumulative elapsed time, it is possible to suppress the failure of the

mechanical relays

61, 62, 63. ..

Embodiment 3.
FIG. 6 is a diagram showing a state in which the motor drive device according to the third embodiment drives the motor with a star connection. The motor drive device 150 according to the third embodiment is different from the motor drive device 150 according to the first embodiment in that the input unit 110 and the sensor unit 120 are connected to each other. The input unit 110 accepts an input operation of the target set value. The input unit 110 includes a display unit 111 and an operation unit 112. The set target value input through the operation unit 112 is displayed on the display unit 111. The user confirms the set target value displayed on the display unit 111, and then stores the target set value in the storage unit 91.

The sensor unit 120 includes a sensor that detects the state of air. Here, a case where the measured temperature acquired by the temperature sensor 121 is transmitted to the control unit 90 will be described as an example. Therefore, the target set value input through the operation unit 112 is the target set temperature. The control unit 90 stores the actually measured temperature received from the sensor unit 120 in the storage unit 91.

The motor drive device 150 according to the third embodiment uses the temperature width upper limit value and the temperature width lower limit value set in advance in the storage unit 91 and the target set temperature set by the user, and the measured temperature acquired from the sensor unit 120. Whether or not switching is possible is determined based on. The upper limit of the temperature range used for the determination is the sum of the target set temperature and the upper limit of the temperature width, and the lower limit is the value obtained by subtracting the lower limit of the temperature width from the target set temperature. The upper limit value of the temperature width and the lower limit value of the temperature width may be the same value. When the measured temperature falls within this temperature range, the difference between the target set temperature set by the user and the room temperature is small, indicating that the load until the room temperature reaches the target set temperature is small.

FIG. 7 is a flowchart showing the flow of switching control using the measured temperature of the motor drive device according to the third embodiment. After the start of steady operation, when the load strength of the motor 70 changes and it becomes necessary to switch the connection state of the stator windings of the motor 70, the control unit 90 performs the process of FIG. 7 in addition to the process shown in FIG. I do. In step S31, the control unit 90 reads out the target set temperature, the temperature width upper limit value, the temperature width lower limit value, and the measured temperature stored in the storage unit 91. In step S32, the control unit 90 acquires the switching permission flag stored in advance in the storage unit 100, and determines whether or not the switching permission flag is “valid”.

If the switching permission flag is "invalid", the result is No in step S32, and the process ends. When the switching permission flag is "valid", Yes is set in step S32, and the process proceeds to step S33. In step S33, the control unit 90 determines whether the measured temperature exceeds the "target set temperature + temperature range upper limit value" or the measured temperature is less than the "target set temperature-temperature width lower limit value". If the measured temperature is equal to or less than "target set temperature + upper limit of temperature width" or equal to or higher than "target set temperature-lower limit of temperature width", No is obtained in step S33, and the process proceeds to step S36. If the measured temperature exceeds the "target set temperature + temperature range upper limit value" or the measured temperature is less than the "target set temperature-temperature width lower limit value", the result is Yes in step S33, and the process proceeds to step S34.

The processing of steps S34 and S35 is the same as the processing of steps S14 and S15 shown in FIG.

In step S36, the control unit 90 sets the switching permission flag to "invalid".

The motor drive device 150 according to the third embodiment has

mechanical relays

61, 62, when the measured temperature is equal to or less than "target set temperature + upper limit of temperature width" or more than or lower to "target set temperature-lower limit of temperature width". The measured temperature reaches the target set temperature without switching 63. Therefore, the motor drive device 150 according to the third embodiment can suppress the number of times the

mechanical relays

61, 62, 63 are switched, and can suppress the failure of the

mechanical relays

61, 62, 63.

The input unit 110 may be arranged outside the motor drive device 150. For example, in the case of an air conditioner, if the motor drive device 150 is arranged inside the outdoor unit, the motor drive device 150 can be operated via communication between the indoor unit and the outdoor unit by operating the controller of the indoor unit. The target value may be set in. Further, the connection between the control unit 90 and the input unit 110 is not limited to the wired connection, and may be a wireless connection using infrared communication or wireless communication. Known wireless communication standards such as Wi-Fi (registered trademark), Wi-SUN (Wireless Smart Utility Network), Bluetooth (registered trademark) and NFC (Near Field Communication) can be applied to wireless communication.

Further, in the above description, the switching of the

mechanical relays

61, 62, 63 is suppressed based on the measured temperature measured by the temperature sensor 121, but the temperature distribution in the room is measured by using the infrared sensor, and the temperature distribution is measured in a mesh shape. Of the areas divided into, the

mechanical relays

61, 62, 63 are occupied based on the ratio of the area equal to or less than "target set temperature + temperature range upper limit" or "target set temperature-temperature range lower limit" or more. Switching may be controlled. Further, the determination of switching of the

mechanical relays

61, 62, 63 may be controlled based on the humidity measured by the humidity sensor. Further, even if the switching of the

mechanical relays

61, 62, 63 is suppressed based on the measured values of the pressure sensor that measures the pressure of the refrigerant used in the compressor of the air conditioner or the gas sensor that measures the concentration of the refrigerant. good.

Embodiment 4.
FIG. 8 is a diagram showing a state in which the motor drive device according to the fourth embodiment drives the motor with a star connection. The motor drive device 150 according to the fourth embodiment is different from the motor drive device 150 according to the first embodiment in that it includes a current detection unit 130. The current detection unit 130 measures the currents of the three phases of the U-phase, V-phase, and W-phase of the motor 70, and stores the current value in the storage unit 91.

FIG. 9 is a flowchart showing the flow of switching control using the current detection value of the motor drive device according to the fourth embodiment. After the start of steady operation, when the load strength of the motor 70 changes and it becomes necessary to switch the connection state of the stator windings of the motor 70, the control unit 90 performs the process of FIG. 9 in addition to the process shown in FIG. I do. In step S41, the control unit 90 reads out the switching target current value, the switching current upper limit value, the switching current lower limit value, and the detected current value stored in the storage unit 91. In step S42, the control unit 90 acquires the switching permission flag stored in advance in the storage unit 100, and determines whether or not the switching permission flag is “valid”.

If the switching permission flag is "invalid", the result is No in step S42, and the process ends. When the switching permission flag is "valid", Yes is set in step S42, and the process proceeds to step S43. In step S43, the control unit 90 determines whether the detected current value exceeds the "switching target current value + switching current upper limit value" or the detected current value is less than the "switching target current value-switching current lower limit value". to decide. If the detected current value is equal to or less than "switching target current value + switching current upper limit value" or the detected current value is equal to or greater than "switching target current value-switching current lower limit value", No is obtained in step S43, and the process is performed in step S46. Proceed to. If the detected current value exceeds the "switching target current value + switching current upper limit value" or the detected current value is less than the "switching target current value-switching current lower limit value", Yes in step S43, and the process proceeds to step S44. move on.

The processing of steps S44 and S45 is the same as the processing of steps S14 and S15 shown in FIG.

In step S46, the control unit 90 sets the switching permission flag to "invalid".

The motor drive device 150 according to the fourth embodiment is a mechanical relay 61 when the detected current value is "switching target current value + switching current upper limit value" or less or "switching target current value-switching current lower limit value" or more. , 62, 63 are not switched. Therefore, the motor drive device 150 according to the fourth embodiment can suppress the number of times the

mechanical relays

61, 62, 63 are switched, and can suppress the failure of the

mechanical relays

61, 62, 63.

The current detection unit 130 may detect the two-phase current values and switch the switching unit 60 at the zero crossing point where the load current becomes almost zero, or detect only the one-phase current value and switch the switching unit. You may switch by estimating the time point when the current flowing through 60 is small.

Embodiment 5.
FIG. 10 is a diagram showing the configuration of the air conditioner according to the fifth embodiment. The air conditioner 200 according to the fifth embodiment includes the motor drive device 150 according to any one of the first to fourth embodiments. The air conditioner 200 of the fifth embodiment is a refrigerating machine in which a compressor 101 having a built-in electric motor 70, a four-way valve 102, an outdoor heat exchanger 103, an expansion valve 104, and an indoor heat exchanger 105 are attached via a refrigerant pipe 106. It has a cycle and constitutes a separate type air conditioner.

A compression mechanism 107 for compressing the refrigerant and an electric motor 70 for operating the compression mechanism 107 are provided inside the compressor 101, and the refrigerant circulates from the compressor 101 between the outdoor heat exchanger 103 and the indoor heat exchanger 105. A refrigeration cycle is configured to perform heating and cooling. The configuration shown in FIG. 10 can be applied not only to an air conditioner but also to a refrigerating cycle device including a refrigerating cycle such as a refrigerator and a freezer.

The function of the control unit 90 of the motor drive device 150 according to the first to fourth embodiments is realized by the processing circuit. The processing circuit may be dedicated hardware or a processing device that executes a program stored in the storage device. A microcontroller can be applied to the control device, but the controller is not limited to this.

If the processing circuit is dedicated hardware, the processing circuit may be a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an application-specific integrated circuit, a field programmable gate array, or a combination thereof. Applies to. FIG. 11 is a diagram showing a configuration in which the function of the control unit of the motor drive device according to any one of the first to fourth embodiments is realized by hardware. The processing circuit 39 incorporates a logic circuit 39a that realizes the function of the control unit 90.

When the processing circuit 39 is a processing device, the function of the control unit 90 is realized by software, firmware, or a combination of software and firmware.

FIG. 12 is a diagram showing a configuration in which the control unit of the motor drive device according to any one of the first to fourth embodiments is realized by software. The processing circuit 39 includes a processor 391 that executes the program 39b, a random access memory 392 that the processor 391 uses for the work area, and a storage device 393 that stores the program 39b. The function of the control unit 90 is realized by the processor 391 expanding and executing the program 39b stored in the storage device 393 on the random access memory 392. The software or firmware is written in a programming language and stored in a storage device 393. Processor 391 can exemplify a central processing unit, but is not limited thereto. The storage device 393 applies a semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), or EEPROM (registered trademark) (Electrically Erasable Programmable Read Only Memory). can. The semiconductor memory may be a non-volatile memory or a volatile memory. In addition to the semiconductor memory, the storage device 393 can be applied with a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile Disc). The processor 391 may output data such as a calculation result to the storage device 393 and store the data, or may store the data in an auxiliary storage device (not shown) via the random access memory 392.

The processing circuit 39 realizes the function of the control unit 90 by reading and executing the program 39b stored in the storage device 393. It can be said that the program 39b causes the computer to execute the procedure and the method for realizing the function of the control unit 90.

Note that the processing circuit 39 may realize a part of the functions of the control unit 90 with dedicated hardware and a part of the functions of the control unit 90 with software or firmware.

As described above, the processing circuit 39 can realize each of the above-mentioned functions by hardware, software, firmware, or a combination thereof.

The configuration shown in the above embodiment is an example of the content, can be combined with another known technique, and a part of the configuration is omitted or changed without departing from the gist. It is also possible.

10 AC power supply, 20 reactor, 30 rectifier, 31, 32, 33, 34 rectifier element, 39 processing circuit, 39a logic circuit, 39b program, 40 capacitor, 50 inverter, 51, 52, 53, 54, 55, 56 switching Element, 60 switching unit, 61, 62, 63 mechanical relay, 70 motor, 80 detection unit, 81 voltage detection unit, 82, 130 current detection unit, 90 control unit, 91, 100 storage unit, 101 compressor, 102 squares Valve, 103 outdoor heat exchanger, 104 expansion valve, 105 indoor heat exchanger, 106 refrigerant piping, 107 compression mechanism, 110 input unit, 111 display unit, 112 operation unit, 120 sensor unit, 121 temperature sensor, 140 clock unit, 150 motor drive, 200 air conditioner, 391 processor, 392 random access memory, 393 storage device.

Claims

A switching unit equipped with a plurality of mechanical relays for switching the connection state of the stator windings of the motor to either star connection or delta connection, and
An inverter that applies drive power to the motor and
It has a control unit that controls the switching unit.
In the control unit, the cumulative number of times of switching indicating the number of times the connection state is switched by the switching unit is the number of times of switching in which the electrical opening / closing operation of the mechanical relay is not guaranteed to be performed normally. An electric motor drive device that stops the switching of the connection state at the switching unit when the number of times is exceeded.
The motor drive device according to claim 1, wherein when the cumulative number of switching times exceeds the upper limit of the number of times of switching in the design of the mechanical relay, the switching unit stops the switching of the connection state.
It has a clock unit that measures the elapsed time from the first start of the motor.
The motor drive device according to claim 1 or 2, wherein the control unit causes the switching unit to stop switching of the connection state when the elapsed time exceeds the set time.
An input unit that accepts input operations for target setting values,
It has a sensor unit that measures the state of air, and has a sensor unit.
The motor drive device according to claim 1 or 2, wherein the control unit causes the switching unit to stop switching of the connection state when the value measured by the sensor unit becomes equal to or higher than the target set value.
It has a current detection unit that detects the current flowing through the motor through the switching unit.
The motor drive device according to claim 1 or 2, wherein the control unit switches the connection state at the current zero point of the current flowing through the motor through the switching unit.
An air conditioner including the motor drive device according to any one of claims 1 to 5.