JP6469251B2 - Inverter device and air conditioner - Google Patents

Description

  The present invention relates to an inverter device that converts a DC voltage obtained by rectifying an applied voltage from an AC power source (hereinafter referred to as “power source voltage” as appropriate) into an arbitrary voltage, and an air conditioner including the inverter device.

  Conventional inverter devices use switching elements connected in parallel in order to increase the load current capacity (see, for example, Patent Document 1 below).

Japanese Patent Laying-Open No. 2013-038828 (FIG. 1)

  Since the inverter device shown in Patent Document 1 (hereinafter referred to as “conventional inverter device”) determines the malfunction of the gate circuit of the switching element and the open failure of the switching element based on the temperature difference of the switching element. There is a problem that a temperature detecting element insulated in the vicinity of each switching element is necessary, and the time followability of the temperature is slow, so that a failure cannot be detected immediately.

  Further, since the conventional inverter device stops the device when it is determined to be a failure, there is a problem that the user cannot use the device until the repair of the device or the replacement of the parts is completed.

  The present invention has been made in view of the above, and can be operated without stopping the device even if it is determined to be a failure, and the failure of the device is notified to the outside during the operation. An object of the present invention is to obtain an inverter device that can prompt replacement.

In order to solve the above-described problems and achieve the object, an inverter device according to the present invention includes a first conversion circuit and a first conversion circuit for converting a power supply voltage from a single-phase or three-phase AC power supply into a DC voltage. And a control circuit for controlling the second conversion circuit. The second conversion circuit has a plurality of switching circuits in which two switching elements are connected in series. The plurality of sets of switching circuits are configured to be connected in parallel, and each of the switching elements is provided with a current detection circuit connected in series to each switching element . By detecting that current does not flow in the current detection circuit, an open failure of each switching element connected in series to the current detection circuit is detected, and the operating current is limited by the number of open switching failures. .

  According to the present invention, it is possible to operate without stopping the device even if it is determined as a failure, and to notify the outside of the failure of the device during the operation and prompt the replacement of the parts. Play.

FIG. 3 is a circuit diagram showing a configuration example of an inverter device in the first embodiment The partial circuit diagram which shows the structure for 1 arm of the inverter apparatus in Embodiment 1 Schematic of the outdoor unit in the air conditioner shown as an application example of the inverter device according to Embodiment 1

  Hereinafter, an inverter device and an air conditioner according to an embodiment of the present invention will be described with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

Embodiment 1 FIG.
FIG. 1 is a circuit diagram illustrating a configuration example of an inverter device according to the first embodiment. As shown in FIG. 1, the inverter device 100 of Embodiment 1 is converted by a rectifier 2 that converts an AC voltage applied from an AC power source 1 into a DC voltage, a reactor 3 that improves a power factor, and a rectifier 2. Capacitor 4 as a smoothing circuit that smoothes the DC voltage, voltage detection unit 11 that detects the voltage across capacitor 4, and converts the DC voltage into a three-phase AC voltage to drive a motor 8 that is a three-phase motor, that is, an electric motor. The inverter part 101, the control circuit 9 which produces | generates the PWM signal for controlling the inverter part 101, and the current detection circuits 21-38 are provided. Between the inverter part 101 and the motor 8, the current measuring devices 10a and 10b which measure a motor current are provided. Among these components, the rectifier 2 constitutes a first conversion circuit that converts an AC voltage applied from an AC power source, that is, a power supply voltage, into a DC voltage, and the inverter unit 101 is supplied from the first conversion circuit. A second conversion circuit for converting a DC voltage into an AC voltage is configured. In FIG. 1, a three-phase power source is illustrated as the AC power source 1, but a single-phase power source may be used.

  Inverter device 100 of Embodiment 1 is an air conditioner, refrigerator, washing dryer, refrigerator, dehumidifier, heat pump water heater, showcase, vacuum cleaner, fan motor, ventilation fan, hand dryer, induction heating electromagnetic cooking. It can be used as a device for driving a motor in a device such as a container.

  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 modules 5, 6, and 7 each include six switching elements 5a, 5b, 5c, 5d, 5e, and 5f. Switching elements 5a, 5c and 5e constitute an upper arm, and switching elements 5b, 5d and 5f constitute a lower arm.

  The switching element 5a of the upper arm and the switching element 5b of the lower arm are connected in series, and the switching elements 5a and 5b, that is, the pair of switching elements connected in series constitute a set of switching circuits. The same applies to the switching elements 5c and 5d and the switching elements 5e and 5f. In addition, although the structure by which two switching elements are connected in series is disclosed in FIG. 1, the structure by which two or more switching elements are connected in series may be sufficient.

  One set of switching circuits is connected in parallel to constitute the inverter unit 101. In FIG. 1, a switching circuit composed of switching elements 5a and 5b, a switching circuit composed of switching elements 5c and 5d, and a switching circuit composed of switching elements 5e and 5f are connected in parallel.

  In FIG. 1, a three-phase motor is illustrated as the motor 8, but a single-phase motor may be used. When the motor 8 is a single phase motor, the number of inverter modules constituting the inverter unit 101 may be two.

  In the first embodiment, even when the current capacities of the switching elements 5a, 5b, 5c, 5d, 5e, and 5f are small, a large current capacity can be obtained by parallelizing the switching elements for each phase as shown in FIG. Can be realized. The configuration of the inverter modules 6 and 7 is the same as that of the inverter module 5. For simplification, reference numerals in the inverter modules 6 and 7 are omitted in FIG.

  The current detection circuits 21, 22, and 23 detect currents flowing through the switching elements 5 b, 5 d, and 5 f of the lower arm of the inverter module 5, and the current detection circuits 24, 25, and 26 are switching elements of the lower arm of the inverter module 6. The currents flowing through 5b, 5d, and 5f are detected, and the current detection circuits 27, 28, and 29 detect the current that flows through the switching elements 5b, 5d, and 5f of the lower arm of the inverter module 7. The current detection circuits 30, 31 and 32 detect the current flowing through the switching elements 5 a, 5 c and 5 e of the upper arm of the inverter module 5, and the current detection circuits 33, 34 and 35 are the switching elements of the upper arm of the inverter module 6. The currents flowing through 5a, 5c and 5e are detected, and the current detection circuits 36, 37 and 38 detect the current flowing through the switching elements 5a, 5c and 5e of the upper arm of the inverter module 7.

  The control circuit 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 detection circuits 10a and 10b. Specifically, PWM signals Up, Vp, Wp, Un, Vn, Wn for controlling the on / off states of the switching elements for each phase and arm are generated and output to inverter 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. It is a PWM signal for controlling the on / off state of the element. The PWM signal is a pulse-like signal that takes either a high value indicating on or closed, or a low value indicating off or open, and is repeatedly turned on and off. The width of a pulse, that is, a period during which ON is continued is called a pulse width. Since the same arm of the same phase is composed of three switching elements, the control circuit 9 determines the pulse width based on the current that flows when the three switching elements are turned on. That is, the PWM signal is generated by regarding the three switching elements as one switching element having a large current capacity.

  Any element may be used as the switching element, but a wide band gap semiconductor such as GaN (gallium nitride), SiC (silicon carbide: silicon carbide), diamond, or the like can be used. By using a wide band gap semiconductor, the withstand voltage is high and the allowable current density is also high, so that the module can be miniaturized. Since the wide band gap semiconductor has high heat resistance, it is possible to reduce the size of the radiating fin of the radiating portion.

  Here, a general inverter for driving a three-phase motor will be described as a comparative example. In general, when an inverter is used to drive a three-phase motor, the inverter includes 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. Prepare. Therefore, the inverter of the comparative example includes a total of three pairs, that is, six switching elements for three phases. On the other hand, when the switching element is mounted as a chip, the yield deteriorates if the chip area is increased. If the chip area is reduced, the yield when removing from the wafer can be improved. In particular, when SiC is used as the switching element, since the wafer is expensive, it is desirable to reduce the chip area in order to reduce the price. When the current capacity may 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, when the chip area is reduced, the current capacity is reduced. For this reason, in the inverter module of the comparative example, that is, the inverter module that drives the three-phase motor with six switching elements, it is difficult to achieve both low cost and high current. On the other hand, in this embodiment, it is possible to realize both a reduction in price and an increase in current 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 shown in the comparative example, and inverter modules 5, 6 composed of six switching elements of the present embodiment. , 7 can share the basic part. For this reason, 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 simple modification. 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 or similar modules. Therefore, the inverter modules 5, 6 and 7 for large current capacity can be manufactured at low cost. For example, one module for three phases composed of six switching elements is used for a home air conditioner, and three modules are used for a commercial air conditioner as shown in FIG. The inverter part 101 provided with 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 called a single pair inverter, that is, a switching element for three phases, that is, three pairs of switching elements. A module mounted as a single module 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 upper-arm switching element in the same phase and one lower-arm switching element in the same phase. On the other hand, in the present embodiment, there are three upper-arm switching elements in the same phase and three lower-arm switching elements in the same phase. Therefore, if 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.

  Since actual switching elements have performance variations, current imbalance due to performance variations occurs when they are configured with a parallel circuit. Therefore, the number of switching elements configured in parallel is usually adjusted so that the current flowing through each switching element does not exceed the current capacity Am of each switching element, taking into account the performance variation of the switching elements. For example, when configuring an inverter device with a current capacity of 15 [A] to configure an inverter device with a current capacity of 30 [A], the parallel number is set to “3” instead of “2”. Thus, by increasing the current capacity of the inverter module, the current rating per switching element due to current imbalance is not exceeded.

  However, when any one of the switching elements configured in the parallel circuit has an open failure, a phenomenon occurs in which the other switching elements of the parallel circuit continue to operate exceeding the current rating. Switching element failures include when the chip is short-circuited due to thermal destruction, etc., and when the switching element chip, the circuit that connects the chip, and the circuit that drives the switching element fail due to deterioration over time, etc. There is.

  When one switching element of the parallel circuit has a short circuit fault, it can be easily detected by an overcurrent to the inverter device. However, when one switching element of the parallel circuit has an open fault, the entire inverter device has a particular functional problem. Therefore, it is necessary to individually detect the opening of the switching element chip.

  On the other hand, when one switching element of the parallel circuit becomes an open failure, the function of the inverter (except for the problem that the current flowing through the switching element exceeds the current rating and continues to operate when the load current of the inverter device is large) For example, the function of operating the motor is not impaired. In particular, when applying an inverter device to a motor such as an air conditioner, if the temperature of the space you want to adjust the temperature is close to the target temperature, it will continue to operate at a load smaller than the rating. Long time to continue operation with a load smaller than the rated value. Therefore, although it takes a long time to reach the target temperature, it is more beneficial for the user to maintain the operation with a small load than to stop the device, and the user's comfort is not impaired.

  FIG. 2 is a partial circuit diagram showing the configuration of one arm of the inverter device according to the first embodiment. FIG. 2 shows switching elements 5b, 5d, and 5f that constitute the U-phase lower arm. Now, an ON signal is input from the control circuit 9 shown in FIG. 1 to the switching elements 5b, 5d, and 5f of the U-phase lower arm, and the switching elements 5b, 5d, and 5f are simultaneously turned on. At this time, currents flowing through the switching elements 5b, 5d, and 5f are I1, I2, and I3, respectively. Note that these currents I1, I2, and I3 vary depending on the characteristic difference of each switching element, but it may be considered that substantially the same current flows.

  Here, it is assumed that one switching element becomes an open failure and no current can flow. At this time, since there are two switching elements through which current can flow, the current that has been divided into three currents is divided into two parts, and the current that flows through each switching element increases. An excess of concern arises.

  For example, it is assumed that an element having a current rating of 15 [A] is used for each of the switching elements 5b, 5d, and 5f and the load current that is a current flowing through the motor 8 is operated at 33 [A]. At this time, the current flowing per switching element is about 11 (= 33/3) [A]. When one switching element fails, the current flowing per switching element increases to about 16.5 (= 33/2) [A], and the current exceeding the rating with respect to the current rating of 15 [A] is constantly increased. Will flow.

  Next, the operation of the main part of inverter device 100 in the first embodiment will be described with reference to the drawings in FIGS.

  First, in the inverter device 100 configured as described above, it is assumed that any one (for example, 5f) of the three parallel switching elements 5b, 5d, and 5f illustrated in FIG. Then, the current I3 does not flow through the switching element 5f and the current detection circuit 23. When the arithmetic unit 12 detects that the current signal from the current detection circuit 23 disappears, the three switching elements constituting the U-phase lower arm operate with two switching elements (in this example, the switching elements 5b and 5d). And a limit signal is sent to the control circuit 9. When the control circuit 9 receives the limit signal, the current flowing through the motor 8 (hereinafter referred to as “motor operating current” or simply “operating current” as appropriate) so that no current exceeding the rated current of the element flows through one switching element. Called).

  For example, when an element having a current rating of 15 A is used for the switching element described above, the motor is set such that the maximum value of the motor operating current (hereinafter referred to as “motor maximum operating current” as appropriate) does not exceed 30 [A]. Limit the operating current. At this time, a margin is set in consideration of the performance variation of the switching element so that the motor operation current does not exceed a first current value of 30 [A] or less (for example, about 26 [A]), or the first current The motor operating current may be limited so as to be less than the value.

  The control circuit 9 limits the motor operating current and transmits a signal to the display unit 13 (see FIG. 1). When the display unit 13 receives the signal, the display unit 13 displays a sign that prompts the user to replace the inverter device 100. Note that the sign for prompting replacement may be a technique of blinking an LED provided on the display unit 13 or may be a character display on the liquid crystal panel. That is, any mechanism may be used as long as it is a means or method (hereinafter collectively referred to as “mechanism”) that can indicate to the user that the inverter device 100 needs to be replaced.

  Further, instead of the display unit 13, a device that generates sound may be used. When the user approaches the device, such as turning on the power of the device or starting an operation, an error sound is output and notified. It may be a mechanism.

  As described above, according to the inverter device according to the first embodiment, a plurality of sets of switching circuits are connected in parallel, each of the switching elements is provided with a current detection circuit, and the detection result of the current detection circuit is used. Therefore, it is possible to limit the operating current according to the number of faulty switching elements and to detect the fault of the switching elements without stopping the inverter device. It is possible to notify the user.

  Moreover, according to the inverter apparatus which concerns on Embodiment 1, since the user can continue use of the said inverter apparatus after grasping | ascertaining the abnormality of an inverter apparatus, the situation which loses the power conversion function by an inverter apparatus is avoided. It is also possible to secure time for parts replacement or repair.

  In the first embodiment, the number of parallel switching of one arm switching element, that is, one set of switching circuits has been described as 3, but the parallel number may be configured to be 2 or 4 or more. However, most of the general-purpose motor drive inverter modules are three-phase, and if the number of parallel is three, three modules are connected in parallel, so that the inverter device for three-phase motors with three switching elements is a general-purpose product. There is an advantage that it can be easily configured. Therefore, in the case of an inverter device in which the number of parallel switching elements of one arm is 3, there are significant advantages in terms of cost and procurement.

Embodiment 2. FIG.
FIG. 3 is a schematic diagram of the outdoor unit 40 in the air conditioner shown as an application example of the inverter device 100 according to the first embodiment. In FIG. 3, an outdoor unit 40 includes a fan 41 disposed to face a heat exchanger (not shown), a compressor 42 that is a drive target of the inverter device 100 according to the first embodiment, and an implementation. The inverter apparatus 43 comprised so that it might have the function of the inverter apparatus 100 which concerns on this form 1 is illustrated. The inverter device 43 is installed in the outdoor unit 40 and is configured with electrical wiring so as to control a motor (not shown) provided in the compressor 42. The inverter 100 may be driven not only by the motor of the compressor 42 but also by a motor that drives a blower fan (not shown), or by a motor that rotationally drives a blower fan provided in the indoor unit. It may be.

  Therefore, according to the air conditioner according to the second embodiment, the operation of the air conditioner can be continued even when the inverter device mounted on the air conditioner fails or deteriorates, so that the comfort of the user is improved. Can be avoided.

  Further, according to the air conditioner according to Embodiment 2, the user can grasp the failure or deterioration of the inverter device mounted on the air conditioner, so that there is a time delay for parts replacement or repair. Can be given to the user.

  Further, according to the second embodiment, since a general-purpose inverter module for a three-phase motor can be used, a high-performance air conditioner can be configured at a lower cost.

  Note that the configuration shown in the above embodiment is an example of the configuration of the present invention, and can be combined with another known technique, and a part thereof is omitted without departing from the gist of the present invention. Needless to say, the configuration can be changed.

  DESCRIPTION OF SYMBOLS 1 AC power supply, 2 Rectifier (1st conversion circuit), 3 Reactor, 4 Capacitor, 5-7 Inverter module, 5a-5f Switching element, 8 Motor, 9 Control circuit, 10a, 10b Current measuring device, 11 Voltage detection part , 12 arithmetic unit, 13 display unit, 21-38 current detection circuit, 40 outdoor unit, 41 fan, 42 compressor, 43, 100 inverter device, 101 inverter unit (second conversion circuit).

Claims (6)

A first conversion circuit that converts a power supply voltage from a single-phase or three-phase AC power supply into a DC voltage; a second conversion circuit that converts a DC voltage from the first conversion circuit into an AC voltage; In an inverter device comprising a control circuit for controlling the two conversion circuits,
The second conversion circuit has a plurality of sets of switching circuits in which two switching elements are connected in series,
A plurality of sets of the switching circuits are configured to be connected in parallel, and each of the switching elements is provided with a current detection circuit connected in series to each switching element ,
By detecting that current does not flow in the current detection circuit, an open failure of each of the switching elements connected in series to the current detection circuit is detected, and the operation current is limited by the number of open failure elements. An inverter device characterized by that. The inverter device according to claim 1, wherein information on the switching element having an open failure is notified to the outside.   The inverter device according to claim 1, wherein the switching element is a switching element formed using a wide band gap semiconductor.   4. The inverter device according to claim 1, wherein the plurality of switching elements are modularized for each phase corresponding to the AC voltage to constitute an inverter module. 5.   The inverter device according to claim 4, wherein the inverter module is an inverter module for a three-phase motor. An air conditioner on which the inverter device according to any one of claims 1 to 5 is mounted,
The said inverter apparatus rotates the motor of the fan for ventilation mounted in the said air conditioner, or the motor for compressors. The air conditioner characterized by the above-mentioned.

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