JP6761466B2 - Electric motor drive and air conditioner - Google Patents

Description

The present invention relates to an electric motor drive device and an air conditioner including a switching element.

A technique for driving an electric motor by PWM (Pulse Width Modulation) control using a switching element is known. Patent Document 1 discloses an example of PWM control.

When the switching element is mounted as a chip, increasing the chip area deteriorates the yield. When the chip area is reduced, the yield at the time of taking out from the wafer can be improved, so that the price can be reduced.

Japanese Patent No. 4675902

According to the conventional technology, when the switching element is mounted as a chip, the price can be reduced by reducing the chip area. However, if the chip area is reduced, the current capacity is reduced, so that a plurality of chips are used and connected in parallel. For this reason, the current does not flow evenly due to the variation in the characteristics of each chip, and the current is concentrated only on a specific chip. In order to increase the current by connecting in parallel, it is an issue to suppress the variation in the characteristics of this chip. In addition, when multiple chips are used and connected in parallel to increase the current, the current capacity is ideally several times the current capacity of a single chip in parallel, but the current is suppressed in consideration of the above variation. As a result, there is a problem that the current capacity cannot be increased to an ideal value even if the current capacity is parallelized. For this reason, in an electric motor drive device using a switching element, there is a problem that it is difficult to achieve both a low price and a large current.

The present invention has been made in view of the above, and an object of the present invention is to obtain an electric motor drive device capable of achieving both a low price and a large current.

In order to solve the above-mentioned problems and achieve the object, the electric motor drive device according to the present invention is an electric motor drive device for driving a three-phase electric motor, and each of the three inverters has four or more switching elements. A module, a control unit that outputs a first PWM signal and outputs a second PWM signal, three drive control units that are inserted between the control unit and three inverter modules, a current protection unit, and a current protection unit. Each of the three inverter modules measures the current flowing through the switching element for each switching element pair, which is two upper and lower switching elements connected in series among four or more switching elements. A current measuring unit is provided, and each of the three drive control units is connected to the control unit by first and second signal lines, and the control unit connects the first PWM signal and the second PWM signal, respectively. Outputs to the first signal line and the second signal line, and each of the three drive control units is connected by one of the three inverter modules, the three third signal lines, and the three fourth signal lines. Each of the three drive control units outputs three first individual PWM signals, each of which is the same signal as the first PWM signal, to the three third signal lines, respectively, and the three drive control units. Each outputs three second individual PWM signals, each of which is the same signal as the second PWM signal, to each of the three fourth signal lines. Drive control unit adds the measurement result of the current output from the current measuring unit for each switching element pairs, and outputs to the control unit and the current protection unit as one combined current for each inverter module, the control unit, combining When the current exceeds the threshold value, all the switching elements of the inverter module whose combined current exceeds the threshold value are stopped, and the current protection unit further synthesizes the combined currents of each of the three inverter modules to obtain the total generated current. when the total combined current is greater than the threshold, Ru stops all switching elements of the three inverter module.

The electric motor drive device according to the present invention has the effect of being able to achieve both a low price and a large current.

The figure which shows the structural example of the electric motor drive device which concerns on Embodiment 1. The figure which shows the structural example of the drive control part of Embodiment 1. The figure which shows the structural example of the control circuit of Embodiment 1. The figure which shows the configuration example of the power conversion apparatus which has the shunt resistor between each general-purpose inverter module of Embodiment 1 and the main circuit capacitor, respectively The figure which shows the structural example of the air conditioner of Embodiment 2.

The electric motor drive device and the air conditioner according to the embodiment of the present invention will be described in detail below with reference to the drawings. The present invention is not limited to this embodiment.

Embodiment 1.
FIG. 1 is a diagram showing a configuration example of an electric motor drive device according to a first embodiment of the present invention. As shown in FIG. 1, the electric motor drive device 100 of the present embodiment includes a rectifier 2 that rectifies an alternating current input from an alternating current power supply 1 into a DC current, a capacitor 4 connected in parallel to the rectifier 2, and a rectifier 2. The reactor 3 connected between the inverter 4 and the drive control units 10a, 10b, 10c, the voltage detection unit 11 that detects the voltage across the capacitor 4, and the rectifier 2 are connected in parallel to transmit three-phase DC current. It includes a motor 8 which is a three-phase motor by converting it into an alternating current, that is, an inverter unit 101 for driving an electric motor, and a control unit 9 for generating a PWM signal for controlling the inverter unit 101. The inverter unit 101 is provided with current measuring units 12a to 12c, 13a to 13c, and 14a to 14c for measuring the motor current flowing through the motor 8.

The electric motor drive device 100 of the present embodiment includes an air conditioner, a refrigerator, a washer / dryer, a refrigerator, a dehumidifier, a heat pump type water heater, a showcase, a vacuum cleaner, a fan motor, a ventilation fan, a hand dryer, and an induction heating electromagnetic wave. It can be used as a device for driving a motor in a cooker or the like.

The inverter unit 101 includes an inverter module 5 corresponding to the U phase, an inverter module 6 corresponding to the V phase, and an inverter module 7 corresponding to the W phase. The inverter module 5, the inverter module 6 and the inverter module 7 are connected in parallel. Each of the inverter modules 5, 6 and 7 includes switching elements 5a, 5b, 5c, 5d, 5e and 5f. In the present embodiment, the switching elements 5a, 5c, 5e form an upper arm, and the switching elements 5b, 5d, 5f form a lower arm. Even when the current capacities of the switching elements 5a, 5b, 5c, 5d, 5e, and 5f are small, a large current capacity can be realized by parallelizing the switching elements as shown in FIG. The switching element 5a and the switching element 5b, the switching element 5c and the switching element 5d, the switching element 5e and the switching element 5f each form a switching element pair connected in series. Each switching pair is connected in parallel. The configurations of the inverter modules 6 and 7 are the same as those of the inverter module 5. For the sake of simplicity, the reference numerals of the switching elements 5a, 5b, 5c, 5d, 5e, and 5f in the inverter modules 6 and 7 are omitted in FIG.

The control unit 9 is connected to the drive control units 10a, 10b, and 10c by three signal lines, and is connected to the voltage detection unit 11. The drive control units 10a, 10b, and 10c are connected to the control unit 9 by three signal lines, respectively. Further, the drive control units 10a, 10b, and 10c are connected to the inverter modules 5, 6, and 7 by six signal lines, respectively. Further, the inverter module 5 is connected to the current measuring units 12a, 12b, 12c by one signal line each, and the inverter module 6 is connected to the current measuring units 13a, 13b, 13c by one signal line each. , The inverter module 7 is connected to the current measuring units 14a, 14b, 14c by one signal line each.

The control unit 9 controls the inverter unit 101 based on the voltage detected by the voltage detection unit 11 and the motor current measured by the current measurement units 12a to 12c, 13a to 13c, and 14a to 14c. The current measuring units 12a to 12c, 13a to 13c, and 14a to 14c are current measuring instruments using a shunt resistor. Specifically, the control unit 9 generates PWM signals Up, Vp, Wp, Un, Vn, Wn for controlling the on / off state of the switching element for each phase and arm, and via the drive control units 10a to 10c. Is output to the inverter unit 101. Up, Vp, Wp are PWM signals for controlling the on / off state of the switching element of the upper arm of the U, V, W phase, and Un, Vn, Wn are the switching of the lower arm of the U, V, W phase. This is a PWM signal for controlling the on / off state of the element. The PWM signal is a pulse-shaped signal that takes either a high value indicating on or a low value indicating off. The width of the pulse, that is, the period during which the ON is continuous, is called the pulse width. Since the same arm of the same phase is composed of three switching elements, the control unit 9 determines the pulse width based on the current flowing when the three switching elements are turned on. That is, the three switching elements are regarded as one switching element having a large current capacity, and a PWM signal is generated.

The drive control unit 10a generates a PWM signal for PWM driving the switching elements 5a, 5c, 5e and 5b, 5d, 5f based on the PWM signals of Up and Un generated by the control unit 9. Specifically, in the case of the inverter module 5 corresponding to the U phase, the control unit 9 outputs two signals, Up and Un, which are PWM signals corresponding to the U phase, to the drive control unit 10a, and the drive control unit 10a. Up is duplicated in three at 10a, the duplicated signal is output to the switching elements 5a, 5c, and 5e as PWM signals, Un is duplicated in three, and the duplicated signal is used as a PWM signal in the switching elements 5b, 5d. , 5f respectively. Similarly, in the V-phase inverter module 6 and the W-phase inverter module 7, the drive control unit 10b and the drive control unit 10c are for PWM driving the switching element based on the PWM signal generated by the control unit 9. The PWM signal is duplicated and output.

Although FIG. 1 shows a case where the motor 8 has three phases, the number of phases of the motor is not limited to the example of FIG. Even when the motor 8 is not three-phase, the configuration and operation of the present embodiment can be applied by using the inverter modules for the number of phases.

As described above, the electric motor driving device 100 of the present embodiment drives the motor 8 which is an electric motor having the first number of phases, and the first number is an integer of 2 or more, and in the example of FIG. The number of 1 is 3. Further, when the second number is the same as the first number, the electric motor drive device 100 of the present embodiment is a third number which is twice the number of the fourth number which is an integer of 2 or more. Control with a second number of inverter modules, each of which has a switching element, and a control unit 9 that outputs a first PWM signal to a first signal line and outputs a second PWM signal to a second signal line. The drive control units 5, 6 and 7, which are the same number of drive control units as the first number and the same number of the fifth number as the number of the inverter modules inserted between the unit 9 and the second number of inverter modules, are provided. The fourth number is 3 in the example of FIG.

Any element may be used as the switching elements 5a, 5b, 5c, 5d, 5e, and 5f, but wide bandgap semiconductors such as GaN (gallium nitride), SiC (silicon carbide: silicon carbide), and diamond are used. Can be used. By using a wide bandgap semiconductor, the withstand voltage is high and the allowable current density is also high, so that the module can be miniaturized. Since the wide bandgap semiconductor has high heat resistance, it is possible to reduce the size of the heat dissipation fins in the heat dissipation part.

Here, as a comparative example, a general inverter for driving a three-phase motor will be described. Generally, when a three-phase motor is driven by using an inverter, the inverter has a switching element pair composed of one switching element of the upper arm and one switching element of the lower arm connected in series for each phase. Be prepared. Therefore, the inverter of the comparative example includes a total of 3 pairs, that is, 6 switching elements for 3 phases. On the other hand, when the switching element is mounted as a chip, the yield deteriorates when the chip area is increased. When the chip area is reduced, the yield at the time of taking out from the wafer can be improved. In particular, when SiC is used as the switching element, the wafer is expensive, so it is desirable to reduce the chip area in order to reduce the price. When the current capacity can be small, such as when used in a home air conditioner, the price can be reduced by using an inverter module that controls three phases with six switching elements with a small chip area. it can.

However, the smaller the chip area, the smaller the current capacity. Therefore, in the inverter module of the comparative example, that is, the inverter module in which the three-phase motor is driven by six switching elements, it is difficult to achieve both low price and large current. On the other hand, in the present embodiment, both low cost and large current can be realized by using switching elements having a small current capacity in parallel. Further, as shown in FIG. 1, one inverter module for three phases composed of six switching elements and the inverter modules 5, 6 and 7 composed of six switching elements of the present embodiment are basic. Parts can be shared. Therefore, as the inverter modules 5, 6 and 7, one inverter module for three phases composed of six switching elements can be used as it is or by a simple change.

In other words, one inverter module for three phases and the inverter modules 5, 6 and 7 shown in FIG. 1 can be manufactured as the same module. Therefore, inverter modules 5, 6 and 7 for large current capacities can be manufactured at low cost. As an example, a household air conditioner uses one module for three phases composed of six switching elements, and a commercial air conditioner uses three modules as shown in FIG. The inverter unit 101 including the above can be used. Hereinafter, in order to distinguish from the inverter unit 101 of the present embodiment, an inverter using one pair of switching elements per phase as in the comparative example is referred to as a single pair inverter, and switching elements for three phases, that is, three pairs of switching elements. Is called a single inverter module.

As shown in FIG. 1, the inverter module 5 includes three pairs of switching elements. In a single-pair inverter, there is one switching element for the upper arm of the same phase and one switching element for the lower arm of the same phase. On the other hand, in the present embodiment, the number of switching elements of the upper arm having the same phase is three, and the number of switching elements of the lower arm having the same phase is three. Therefore, assuming that the current capacity of the mounted switching element is Am, the current capacity of the inverter module in which the three switching elements are connected in parallel is ideally 3 × Am.

In the configuration example of FIG. 1, the drive control unit 10a has a function of generating individual PWM signals of the switching elements 5a, 5b, 5c, 5d, 5e, and 5f from the PWM signal generated by the control unit 9. There is. Thereby, the inverter modules 5, 6 and 7 of the present embodiment can be shared with the single inverter module in the module manufacturing.

Generally, in an inverter module for driving a motor, the N line of the lower arm is connected outside the module, and a resistor is inserted between the connection point and the switching element of the lower arm to detect the current, that is, the switching element pair. In many cases, a three-shunt current detection method in which a current measurement unit is provided for each is adopted. Although FIG. 1 illustrates a configuration example in which a three-shunt current detection method is used for the lower arm, the lower arm may also be a one-shunt current detection method connected inside the module.

Next, the drive control unit 10a will be described. FIG. 2 is a diagram showing a configuration example of the drive control unit 10a of the present embodiment. In the present embodiment, not only the inverter module but also the control unit 9 is provided with the drive control unit 10a so that it can be shared as much as possible with the case of the single-pair inverter. That is, in the electric motor drive device 100 of the present embodiment, the number of signal lines for outputting the PWM signal connected to the control unit 9 is six as in the case of a general single-pair inverter.

As shown in FIG. 2, the drive control unit 10a includes an addition unit 21 and a protection unit 22. The addition unit 21 adds the three motor currents detected by the three-shunt method, that is, the three motor currents measured by the current measurement units 12a to 12c, and outputs the combined current to the control unit 9. The protection unit 22 duplicates Up and Un, which are two signals corresponding to the inverter module 5 among the PWM signals output from the control unit 9, into three each, and outputs a total of six PWM signals. The three signals replicated from Up are input to the switching elements 5a, 5c, and 5e of the upper arm of the inverter module 5. The three signals replicated from Un are input to the switching elements 5b, 5d, and 5f on the lower side of the inverter module 5. The drive control units 10b and 10c also have the same configuration as the drive control unit 10a.

By configuring the drive control unit 10a as described above, the number of signal lines for outputting the PWM signal connected to the control unit 9 can remain six as in the case of a general single-pair inverter. ..

That is, in the electric motor drive device 100 of the present embodiment, one of the fifth number of drive control units, that is, one of the drive control units 10a, 10b, and 10c and the control unit 9 are the first and third units. It is connected by a second signal line. Further, one of the fifth number of drive control units and one of the inverter modules 5, 6 and 7 are the third signal line of the sixth number and the fourth signal line of the seventh number. Connected with. One of the fifth number of drive control units is the same signal as the first PWM signal, that is, the first individual PWM of the eighth number, which is a duplicated signal of the first PWM signal. The second of the ninth number, which outputs the signal to the third signal line of the sixth number and is the same signal as the second PWM signal, that is, the signal obtained by replicating the second PWM signal. The individual PWM signals are output to the fourth signal line of the seventh number. The sixth number, the seventh number, the eighth number, and the ninth number are the same as the fourth number. When one of the fifth number of drive control units is the drive control unit 10a, the first and second signals are Up and Un, and one of the fifth number of drive control units drives. In the case of the control unit 10b, the first and second signals are Vp and Vn, and when one of the fifth number of drive control units is the drive control unit 10c, the first and second signals. Are Wp and Wn.

Further, the motor drive device 100 of the present embodiment can output the three motor currents detected by the three-shunt method as one combined current. As a result, the number of signal lines for inputting the measurement result of the motor current to the control unit 9 can be one for each inverter module, that is, a total of three lines.

Further, by configuring the drive control unit 10a as described above, the single pair inverter and the inverter unit 101 can be treated as exactly the same inverter configuration when viewed from the control unit 9, and the configuration of the control unit 9 can be treated as a single pair inverter. It can be shared with the case of. For example, if a microcomputer is used for the control unit 9 and the control unit 9 generates and outputs PWM signals for all switching elements, 18 signal lines are required only for the PWM signals. Since microcomputers are highly versatile and applications that require as many as 18 signal lines are rare, the number of output terminals is usually less than 18. Therefore, a general-purpose microcomputer cannot be used as it is, and there are restrictions such as reducing some functions, or a function of creating a handmade program by the designer and mounting it on the microcomputer is required. In the present embodiment, since the drive control unit 10a described above is used, the number of output terminals of the control unit 9 can be reduced, and the control unit used for the single-pair inverter and the control unit 9 of the present embodiment can be used. Can be standardized.

Here, the hardware configuration of the control unit 9 of the present embodiment will be described. The control unit 9 is realized by a processing circuit. This processing circuit may be a processing circuit that is dedicated hardware, or may be a control circuit including a processor. In the case of dedicated hardware, the processing circuit may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or these. Is a combination of.

When the processing circuit that realizes the control unit 9 is realized by a control circuit including a processor, this control circuit is, for example, the control circuit 200 having the configuration shown in FIG. FIG. 3 is a diagram showing a configuration example of the control circuit 200 of the present embodiment. The control circuit 200 includes a processor 201 and a memory 202. The processor is a CPU (Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microprocessor, processor, DSP (Digital Signal Processor)) and the like. The memory is a non-volatile or volatile semiconductor such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory). This includes memory, magnetic disks, flexible disks, optical disks, compact disks, mini disks, DVDs (Digital Versatile Disk), and the like.

When the processing circuit that realizes the control unit 9 is a control circuit 200 including a processor, the processor 201 is realized by reading and executing a program in which the processing of the control unit 9 stored in the memory 202 is described. The memory 202 is also used as a temporary memory in each process performed by the processor 201.

Although FIGS. 1 and 2 show an example in which the motor current is measured for each phase, the motor current does not have to be measured for each phase, and the two phases need to be in equilibrium with the three phases of the motor 8. The motor current may be measured. In this case, the current measuring unit may be provided in two phases, which is one less than the number of phases of the motor 8, and two combined currents are input to the control unit 9. It is known that the current for three phases can be detected even if the current detection is one less than the number of phases of the motor 8, and the control unit 9 generates a PWM signal by using two motor currents as in the known technique. be able to.

Next, the measurement of the motor current of this embodiment will be described. In the case of the three-shunt current detection method, the switching element of the lower arm and the N line are not connected to the inverter modules 5 to 7, and nine shunt resistors are inserted. As described above, the switching elements of the lower arm may be integrated and one current measuring unit may be provided for one inverter module on the N line, that is, one shunt method may be used, but this embodiment Then, an example in which nine shunt resistors, that is, nine current measuring units are used without being integrated so that each switching element can be protected from a short circuit will be described.

The current measuring units 12a to 12c, 13a to 13c, and 14a to 14c provided with a shunt resistor detect the motor current used for control for driving the motor 8 and prevent an excessive current from flowing to the switching element due to the shunt resistor. It also has a protective function. Assuming that the switching elements 5a, 5c, 5e have no characteristic variation and the switching elements 5b, 5d, 5f have no characteristic variation, an ideal current of 3 × Am flows through the inverter module 5 and each switching element has a current of 3 × Am. It flows evenly. Therefore, if the current flowing through the entire inverter module 5 is measured, it can be determined whether or not an excessive current is flowing in each switching element. That is, even if one current measuring unit is used instead of the current measuring units 12a to 12c, it is possible to protect the switching element from an excessive current.

However, when there are variations in the characteristics of the switching elements, the currents flowing through the switching elements are not uniform, and switching elements in which a current exceeding the current capacity Am is generated. The variation in the characteristics of the switching element is mainly the variation in the on-resistance and the on-timing. The current level at which the protection function works so that each switching element is not destroyed, that is, the overcurrent protection level is generally unified in the inverter module. The protection level of overcurrent is a constant value, but the current flowing through each switching element in the inverter module differs for each switching element due to variations in the characteristics of the switching element. Therefore, in order to protect each switching element, each switching element must be protected. It is necessary to individually grasp the current flowing through the switching element.

In the case of the one-shunt method, in preparation for variations in the characteristics of the switching element, it is assumed that the current flowing through the switching element is not evenly divided into three equal parts, and a margin is given to the protection level of overcurrent. That is, the protection level of overcurrent is lowered as compared with the ideal case where there is no variation in the characteristics of the switching element. As a result, ideally, a current of 3 × Am should flow, but the operation is performed below the overcurrent protection level with a margin. In the present invention, even though a small chip is used to increase the current, when the one-shunt method is used, the maximum current that can be ideally passed by parallelizing the switching elements is provided in order to provide a margin for the protection level of overcurrent. There arises a problem that the current cannot flow up to 3 × Am.

In the case of the 3-shunt current detection method, since a current measuring unit is provided for each switching element pair, the current flowing through the switching element can be detected without considering the variation in the characteristics of the switching element, so that the overcurrent protection of the switching element is protected. It can be said that it is more suitable than the 1-shunt method because the level can be set and the current can be approached to 3 times the ideal current.

On the other hand, the 3-shunt current detection method is suitable from the viewpoint of overcurrent protection, but the number of current measuring units is nine. In the one-shunt method, three signal lines are required to transmit the measurement result output from the current measurement unit, but in the three-shunt current detection method, the measurement result output from the current measurement unit is transmitted. Nine signal lines are required. It is desirable that the number of signal lines connected to the control unit 9 is small. In particular, when a microcomputer is used as the control unit 9 as described above, it is considered that the number of signal lines is limited. As described above, it is desirable to have a current measuring unit for each switching element from the viewpoint of overcurrent protection, but in controlling the motor 8, a total of three for each phase, or a precondition of three-phase equilibrium. It suffices if the motor currents of the two phases can be measured. Therefore, the drive control unit 10a of the present embodiment has an addition unit 21, and the addition unit 21 outputs the measurement results of three motor currents per inverter module to the control unit 9 as one combined current. ..

If the current flowing through the inverter module is evenly divided into three equal parts, the current three times the motor current measured by the current measuring unit 12a becomes the current detected as the U-phase current of the motor 8. Therefore, it is conceivable to output the motor current measured by the current measuring unit 12a to the control unit 9, but since there are three measurement results of the current measuring units 12a to 12c in this embodiment, these are added. In this embodiment, the measurement results of the current measuring units 12a to 12c are added because the motor current of each phase can be detected more accurately. As a result, as the control method in the control unit 9, the control method in the case of the one-shunt current detection method can be used.

Further, by providing the adder unit 21 in the drive control unit 10a, not only the switching elements can be individually protected, but also three combined currents can be obtained, and protection using the combined currents can be performed. The risk of damage due to is extremely small. Taking the case where the current is concentrated on the switching element due to the variation in the characteristics of the switching element, when the specific switching element on which the current is concentrated is stopped by protection, the current of the stopped switching element is applied to the remaining two elements. Also split. At this time, when the current flowing through the switching element in which the current originally flowed reaches the current flowing through the element stopped due to the overcurrent, the current flowing in an instant increases. As a result, it is possible to protect a specific switching element in which the current is concentrated, but since the current increases faster than the operating time of the overcurrent protection, it is not possible to protect the switching element in which the current has increased due to the effect of stopping the specific switching element. I will say. Since all the switching elements can be protected by the combined current generated by the adder according to the present invention, it is possible to protect the switching elements whose flowing current has not reached the protection level of overcurrent.

Further, since the combined current generated by the adding unit 21 can protect against overcurrent, it can also be used for motor step-out detection and demagnetization current interruption. In this way, by using the combined current generated by the adding unit 21, the number of objects to be protected can be increased, and the safety can be further enhanced.

Further, as described above, since the control unit 9 controls the drive of the motor 8 by using the measurement result by the current measurement unit having a protection function from overcurrent, a current sensor that directly detects the current flowing through the motor 8 is provided. It is possible to reduce the amount and realize the electric motor drive device 100 at low cost.

Further, a current protection unit may be further provided in the configuration example of FIG. 1 to protect another inverter module from the protection operation of one inverter module. FIG. 4 is a diagram showing a configuration example of the electric motor drive device 100a provided with the current protection unit 23. In FIG. 4, of the electric motor drive device 100a, only the control unit 9, the drive control units 10a, 10b, 10c and the portion between them are shown, and the inverter modules 5, 6, 7 and the like are omitted. In the electric motor drive device 100a, the current protection unit 23 provided between the control unit 9 and the drive control units 10a, 10b, 10c further synthesizes the three combined currents generated by the drive control units 10a to 10c. Generates one total current. When the one total current is larger than the threshold value, the current protection unit 23 notifies the control unit 9 of the total current and transmits an abnormality to the drive control units 10a to 10c to transmit the abnormality to the drive control units 10a to 10c. All switching elements are stopped at the same time by the protection part inside. As a result, when even one of the measurement results of the nine current measuring units exceeds the overcurrent protection level, all the switching elements, in other words, all the switching elements included in the three inverter modules are simultaneously used. And it can be protected instantly.

Further, although it is described in FIG. 4 that one total current is generated as current protection, this total current can be used not only for protection but also for controlling the drive of the motor 8 in the control unit 9. I don't care. Further, the control unit 9 may change whether to use a total of three combined currents output from each drive control unit or one total current, depending on the rotation speed of the motor 8. Good. Since the difficulty of current detection decreases in the high rotation speed region, the total current is used in the high rotation speed region, and a total of three combined currents output from each drive control unit are used in the low rotation speed region. You may choose to use it. As a result, the drive stability of the motor 8 can be improved as compared with the case where the total current is always used.

As described above, in the present embodiment, the drive control unit duplicates the PWM signal generated by the control unit 9 and outputs it to each inverter module, and adds the measurement results of the current measurement unit to the control unit 9. Changed to output to. Therefore, it is possible to use the same control unit 9 as the control unit used for the single-pair inverter while protecting each switching element from overcurrent.

Embodiment 2.
FIG. 5 is a diagram showing a configuration example of the air conditioner according to the second embodiment of the present invention. The air conditioner of the present embodiment includes the electric motor drive device 100 or the electric motor drive device 100a described in the first embodiment. Although FIG. 5 shows an example in which the electric motor drive device 100 of the first embodiment is provided, the electric motor drive device 100a may be provided instead of the electric motor drive device 100 of the first embodiment. In the air conditioner of the present embodiment, the compressor 81, the four-way valve 82, the outdoor heat exchanger 83, the expansion valve 84, and the indoor heat exchanger 85 incorporating the motor 8 of the first embodiment are routed through the refrigerant pipe 86. It has an attached refrigeration cycle, that is, a refrigeration cycle device, and constitutes a separate type air conditioner.

A compression mechanism 87 for compressing the refrigerant and a motor 8 for operating the compressor 81 are provided inside the compressor 81, and the refrigerant circulates between the outdoor heat exchanger 83 and the indoor heat exchanger 85 from the compressor 81 to perform heating and cooling. The refrigeration cycle to be performed is configured. The configuration shown in FIG. 5 can be applied not only to an air conditioner but also to a device having a refrigerating cycle such as a refrigerator and a freezer.

Since the air conditioner of the present embodiment includes the electric motor drive device described in the first embodiment, it is possible to realize a large current at a low price.

Further, since a plurality of pairs of switching elements are provided for each phase, it is possible to continue the operation by using another switching element even if the switching element fails. When the switching element is out of order, it is possible to continue the operation with a lower capacity than usual and issue an alarm to the user.

The configuration shown in the above-described embodiment shows an example of the content of the present invention, can be combined with another known technique, and is one of the configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

1 AC power supply, 2 rectifier, 3 reactor, 4 capacitor, 5, 6, 7 inverter module, 5a, 5b, 5c, 5d, 5e, 5f switching element, 8 motor, 9 control unit, 10a, 10b, 10c drive control unit , 11 Voltage detector, 12a, 12b, 12c, 13a, 13b, 13c, 14a, 14b, 14c Current measurement unit, 23 Current protection unit, 81 Compressor, 82 Four-way valve, 83 Outdoor heat exchanger, 84 Expansion valve, 85 Indoor heat exchanger, 86 Rectifier piping, 87 Compression mechanism, 100, 100a Electric motor drive, 101 Inverter section.

Claims (5)

It is an electric motor drive device that drives a three-phase electric motor.
Three inverter modules, each with four or more switching elements,
A control unit that outputs a first PWM signal and outputs a second PWM signal,
Three drive control units inserted between the control unit and the three inverter modules, and
Current protection unit and
With
Each of the three inverter modules is a current for measuring the current flowing through the switching element for each switching element pair which is two upper and lower switching elements connected in series among the four or more switching elements. Equipped with a measuring unit,
Each of the three drive control units is connected to the control unit by a first and second signal line.
The control unit outputs the first PWM signal and the second PWM signal to the first signal line and the second signal line, respectively.
Each of the three drive control units is connected to one of the three inverter modules by three third signal lines and three fourth signal lines.
Each of the three drive control units outputs three first individual PWM signals, each of which is the same signal as the first PWM signal, to the three third signal lines.
Each of the three drive control units outputs three second individual PWM signals, each of which is the same signal as the second PWM signal, to the three fourth signal lines.
The drive control unit adds the measurement results of the current output from the current measurement unit for each switching element pair, and outputs the combined current as one combined current for each inverter module to the control unit and the current protection unit .
When the combined current exceeds the threshold value , the control unit stops all the switching elements of the inverter module in which the combined current exceeds the threshold value .
The current protection unit further synthesizes the combined currents of the three inverter modules to obtain the total current, and when the total current is larger than the threshold value, all the switching elements of the three inverter modules are used. motor driving apparatus Ru is stopped. The electric motor drive device according to claim 1, wherein the four or more switching elements are formed of a wide bandgap semiconductor. The electric motor drive device according to claim 2, wherein the wide bandgap semiconductor is silicon carbide. A motor having a first number of terminals is driven, the first number is an integer of 2 or more, and the terminals of the first number are electric motor drive devices corresponding to different phases.
When the second number is the same as the first number, each of the third number of switching elements has the third number larger than the first number, the second number of inverters. Module and
A control unit that outputs a first PWM signal and outputs a second PWM signal,
A fourth number of drive control units, which is the same number as the first number, inserted between the control unit and the second number of inverter modules, respectively.
Current protection unit and
With
Each of the second number of inverter modules is a current flowing through the switching element for each switching element pair which is two upper and lower switching elements connected in series among the third number of switching elements. Equipped with a current measuring unit, which measures
Each of the fourth number of drive control units is connected to the control unit by a first and second signal line.
The control unit outputs the first PWM signal and the second PWM signal to the first signal line and the second signal line, respectively.
Each of the fourth number drive control units is connected to one of the second number inverter modules by a fifth number third signal line and a sixth number fourth signal line. The fifth number and the sixth number are the same as the fourth number.
Each of the drive control units of the fourth number transmits the first individual PWM signal of the seventh number, which is the same signal as the first PWM signal, to the third signal line of the fifth number. The 7th number is the same as the 4th number.
Each of the drive control units of the fourth number transmits the second individual PWM signal of the eighth number, which is the same signal as the second PWM signal, to the fourth signal line of the sixth number. The eighth number is the same as the fourth number.
The drive control unit adds the measurement results of the current output from the current measurement unit for each switching element pair, and outputs one combined current for each inverter module to the control unit and the current protection unit .
When the combined current exceeds the threshold value , the control unit stops all the switching elements of the inverter module in which the combined current exceeds the threshold value .
The current protection unit further synthesizes the combined current for each of the second number of inverter modules to obtain the total current, and when the total current is larger than the threshold value, the second number of inverter modules All the switching elements are stopped, and the total current is output to the control unit.
The control unit is an electric motor driving device that generates the first PWM signal and the second PWM signal by using the total current. The electric motor drive device according to any one of claims 1 to 4.
A compressor having an electric motor driven by the electric motor drive device, and
Air conditioner equipped with.

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