Motor drive devices and refrigeration cycle application equipment

Abstract

This motor drive device (1) has an inverter (50) and a control unit (70), and the inverter (50) has first switching elements (51, 52, 53) of an upper arm (50a), first recirculation diodes (51a, 52a, 53a), second switching elements (54, 55, 56) of a lower arm (50b), and second recirculation diodes (54a, 55a, 56a). When an open-circuit failure of any of the first switching elements of the upper arm (50a) has been detected, the control unit (70) outputs a control signal for turning on all of the second switching elements (54, 55, 56) of the lower arm (50b), and when an open-circuit failure of any of the second switching elements of the lower arm (50b) has been detected, the control unit outputs a control signal for turning on all of the plurality of first switching elements (51, 52, 53) of the upper arm (50a).

Description

[Technical field]

[0001] The present disclosure relates to a motor drive device and a refrigeration cycle applied device. [Background technology]

[0002] In an air conditioner, when a motor (e.g., a permanent magnet synchronous motor) is forcibly rotated due to a disturbance factor (e.g., outside wind), the motor works as a generator and generates a regenerative voltage, which may destroy the motor drive device. As a countermeasure, a technology has been proposed in which, when a regenerative voltage above a threshold is detected, a short-circuit operation and an open operation are repeated between the inverter and the motor, thereby suppressing the regenerative voltage generated when the motor is forcibly rotated to below the inverter's withstand voltage (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-284747 A (see, for example, FIG. 1, paragraph 0013) Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the above technology, if an unexpected open or short circuit occurs in the switching elements that make up the inverter due to some factor, the regenerative voltage may cause an excessive current to flow through the motor or an excessive voltage to be applied to a capacitor connected to the inverter, which may cause a malfunction of the motor drive device.

[0005] The present disclosure has been made to solve the above-mentioned problems, and has an object to provide a motor drive device and a refrigeration cycle applied device that can suppress the occurrence of failures due to regenerative voltage. [Means for solving the problem]

[0006] A motor drive device according to the present disclosure includes an inverter that receives a DC voltage from a DC power supply and outputs a voltage to a motor, and a control unit that detects a fault in the inverter and controls the inverter based on the detected fault, the inverter including a plurality of first switching elements of an upper arm connected between a positive side of the DC power supply and the motor, a plurality of first freewheeling diodes each connected in parallel to the plurality of first switching elements, a plurality of second switching elements of a lower arm connected between a negative side of the DC power supply and the motor, and a plurality of second freewheeling diodes each connected in parallel to the plurality of second switching elements, and the control unit includes: During a period in which all of the first switching elements and all of the second switching elements are controlled to be in an off state in order to stop driving of the motor, When an open-circuit failure of any of the first switching elements of the upper arm of the inverter is detected, a control signal is output to turn on all of the second switching elements of the lower arm, and when an open-circuit failure of any of the second switching elements of the lower arm of the inverter is detected, a control signal is output to turn on all of the first switching elements of the upper arm. , and executes a control action.

[0007] Another motor drive device of the present disclosure includes an inverter that receives a DC voltage from a DC power supply and generates a voltage to be output to a motor, and a control unit that detects a fault in the inverter and controls the inverter based on the detected fault, wherein the inverter includes a plurality of first switching elements of an upper arm connected between a positive side of the DC power supply and the motor, a plurality of first freewheeling diodes each connected in parallel to the plurality of first switching elements, a plurality of second switching elements of a lower arm connected between a negative side of the DC power supply and the motor, and a plurality of second freewheeling diodes each connected in parallel to the plurality of second switching elements, and the control unit: During a period in which all of the first switching elements and all of the second switching elements are controlled to be in an off state in order to stop driving of the motor,When a short-circuit failure of any of the first switching elements of the upper arm of the inverter is detected, a control signal is output to turn on all of the plurality of first switching elements of the upper arm, and when a short-circuit failure of any of the second switching elements of the lower arm of the inverter is detected, a control signal is output to turn on all of the plurality of second switching elements of the lower arm. , execute the control action .

[0008] A refrigeration cycle applied device according to the present disclosure includes a refrigeration cycle device having the motor drive device and a motor driven by the motor drive device. Effect of the Invention

[0009] According to the present disclosure, it is possible to suppress the occurrence of failures in the motor drive device due to regenerative voltage. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating a schematic configuration of a motor drive device according to a first embodiment. [Diagram 2] 2 is a circuit diagram showing a configuration of an inverter in FIG. 1. [Diagram 3] 2 is a diagram showing, by bold lines, an example of a current path when a regenerative voltage is generated when all switching elements of the inverter in FIG. 1 are turned off. [Figure 4] 1A is a diagram showing, with a bold line, the path of the regenerative current when all of the switching elements of the lower arm of the inverter in FIG. 1 are turned on, and FIG. 1B is a diagram showing, with a bold line, the path of the regenerative current when all of the switching elements of the upper arm of the inverter in FIG. 1 are turned on. [Diagram 5] 2 is a diagram showing, by bold lines, an example of a path of a regenerative current when an open circuit fault occurs in a switching element of a lower arm of the inverter in FIG. 1. [Figure 6] FIG. 6 is a waveform diagram showing a DC voltage, d-axis and q-axis currents, phase currents, and the rotation speed of the permanent magnet synchronous motor when the open fault in FIG. 5 occurs. [Figure 7] 2 is a diagram showing, by bold lines, an example of a path of a regenerative current when an open circuit fault occurs in a switching element and a free wheel diode of a lower arm of the inverter in FIG. 1. [Figure 8] FIG. 8 is a waveform diagram showing a DC voltage, d-axis and q-axis currents, phase currents, and the rotation speed of the permanent magnet synchronous motor when the open fault in FIG. 7 occurs. [Figure 9] 4 is a flowchart showing fault detection and operation of an inverter of the motor drive device. [Figure 10] 13A and 13B are circuit diagrams showing the path of a current when a fault is detected. [Figure 11] 13A and 13B are circuit diagrams showing the path of a current when a fault is detected. [Figure 12] 13A and 13B are circuit diagrams showing the path of a current when a fault is detected. [Figure 13] 4 is a flowchart showing fault detection and operation of an inverter of the motor drive device. [Figure 14] FIG. 11 is a diagram illustrating a schematic configuration of a motor drive device according to a second embodiment. [Figure 15] FIG. 11 is a diagram illustrating a schematic configuration of a motor drive device according to a third embodiment. [Figure 16] FIG. 11 is a diagram showing the configuration of an air conditioner as a refrigeration cycle applied device according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A motor drive device according to an embodiment and an air conditioner as a refrigeration cycle application device according to an embodiment will be described below with reference to the drawings. The following embodiments are merely examples, and the embodiments can be appropriately combined and each embodiment can be appropriately modified.

[0012] First Embodiment Configuration of the Motor Drive Device 1 is a diagram illustrating a schematic configuration of a motor drive device 1 according to a first embodiment. The motor drive device 1 includes a DC voltage detection unit 40 that detects a DC voltage at an output terminal of a DC power supply 10 and outputs a DC voltage signal indicating the DC voltage, an inverter 50, and a control unit 70. The inverter 50 receives a DC voltage from the DC power supply 10 and outputs a voltage to a motor 30. The motor 30 is a multi-phase (e.g., three phases of U, V, and W) permanent magnet synchronous motor. The control unit 70 detects a failure of the inverter 50 and controls the inverter 50 based on the detected failure.

[0013] The inverter 50 has a plurality of switching elements (also referred to as "first switching elements") 51, 52, 53 of an upper arm 50a connected between the positive side of the DC power supply 10 and the motor 30, and a plurality of free wheel diodes (also referred to as "first free wheel diodes") 51a, 52a, 53a of the upper arm 50a connected in parallel to the plurality of switching elements 51, 52, 53, respectively. The inverter 50 has a plurality of switching elements (also referred to as "second switching elements") 54, 55, 56 of a lower arm 50b connected between the negative side of the DC power supply 10 and the motor 30, and a plurality of free wheel diodes (also referred to as "second free wheel diodes") 54a, 55a, 56a of the lower arm 50b connected in parallel to the plurality of switching elements 54, 55, 56, respectively.

[0014] The control unit 70 performs the following control when an open circuit failure is detected in any of the switching elements 51 to 56. When the control unit 70 detects an open circuit failure in any of the switching elements of the upper arm 50a of the inverter 50 (i.e., one or more of the switching elements 51, 52, and 53), it outputs a control signal to turn on all of the multiple switching elements 54, 55, and 56 of the lower arm 50b, and when the control unit 70 detects an open circuit failure in any of the switching elements of the lower arm 50b of the inverter 50 (i.e., one or more of the switching elements 54, 55, and 56), it outputs a control signal to turn on all of the multiple switching elements 51, 52, and 53 of the upper arm 50a. This control is also called control at the time of an open circuit failure.

[0015] The control unit 70 performs the following control when detecting a short-circuit failure in any of the switching elements 51 to 56. When the control unit 70 detects a short-circuit failure in any of the switching elements of the upper arm 50a of the inverter 50 (i.e., one or more of the switching elements 51, 52, and 53), it outputs a control signal to turn on all of the switching elements 51, 52, and 53 of the upper arm 50a, and when the control unit 70 detects a short-circuit failure in any of the switching elements of the lower arm 50b of the inverter 50 (i.e., one or more of the switching elements 54, 55, and 56), it outputs a control signal to turn on all of the switching elements 54, 55, and 56 of the lower arm 50b. This control is also called control during a short-circuit failure.

[0016] It is desirable for the motor drive device 1 to have a function for performing both the control at the time of an open circuit fault and the control at the time of a short circuit fault described above. However, the motor drive device 1 may be configured to have only one of the functions of the control at the time of an open circuit fault or the control at the time of a short circuit fault described above.

[0017] 2 is a circuit diagram showing the configuration of the inverter 50 of FIG. 1. The inverter 50 is a three-phase voltage-type full-bridge inverter. The inverter 50 has three IGBTs (Insulated Gate Bipolar Transistors) with freewheel diodes 51a, 52a, and 53a connected in parallel to the positive side of the DC power source 10, i.e., three switching elements 51, 52, and 53, and three IGBTs with freewheel diodes 54a, 55a, and 56a connected in parallel to the negative side of the DC power source 10, i.e., three switching elements 54, 55, and 56. The switching elements 51, 52, and 53 and the switching elements 54, 55, and 56 are each connected in series, and the positive and negative neutral points are connected to each phase (i.e., U, V, and W phases) of the motor 30. The motor 30 is connected in a star connection (Y connection) or a delta connection (Δ connection), and a changeover switch for switching the connection state may be provided. The control unit 70 controls the inverter 50 so as to suppress the regenerative voltage, for example, based on the DC voltage detection value detected by the DC voltage detection unit 40.

[0018] 3 is a diagram showing an example of a current path when a regenerative voltage is generated when all of the switching elements 51 to 56 of the inverter 50 in FIG. 1 are turned off (i.e., open), the motor 30 is stopped and the three switching elements 51, 52, 53 of the upper arm 50a and the three switching elements 54, 55, 56 of the lower arm 50b of the inverter 50 are all turned off (i.e., open), and when the motor 30 is forcibly rotated, a regenerative voltage is generated. This regenerative voltage causes a current to flow through the freewheel diodes 51a to 56a of the upper arm 50a and the lower arm 50b, and the current is rectified, and a DC voltage is applied to the DC power source 10. The DC voltage applied to the DC power source 10 is detected by the DC voltage detection unit 40 (shown in FIG. 1), and the detected DC voltage detection value is output to the control unit 70.

[0019] 4(A) is a diagram showing, with a thick line, the path of the regenerative current when all of the switching elements 54, 55, 56 of the lower arm 50b of the inverter 50 in FIG. 1 are turned on and all of the switching elements 51, 52, 53 of the upper arm 50a are turned off. FIG. 4(B) is a diagram showing, with a thick line, the path of the regenerative current when all of the switching elements 51, 52, 53 of the upper arm 50a of the inverter 50 in FIG. 1 are turned on and all of the switching elements 54, 55, 56 of the lower arm 50b are turned on. In the state shown in FIG. 4(A) or FIG. 4(B), the regenerative voltage generated in the motor 30 can be attenuated within the motor 30. Therefore, in the state shown in FIG. 4(A) or FIG. 4(B), Figure 4(A) or Figure 4(B) 1. Since the regenerative current flows through the path indicated by the thick line in FIG. 1, the regenerative voltage is not applied to the DC power supply 10 and the smoothing capacitor 21 connected between the terminals of the DC power supply 10.

[0020] Therefore, in the first embodiment, when the control unit 70 detects an open circuit failure in any of the switching elements 51, 52, 53 of the upper arm 50a of the inverter 50, it turns on all of the multiple switching elements 54, 55, 56 of the lower arm 50b, which is the opposite arm, to form a circuit equivalent to Fig. 4(A). Also, when the control unit 70 detects an open circuit failure in any of the switching elements 54, 55, 56 of the lower arm 50b of the inverter 50, it turns on all of the multiple switching elements 51, 52, 53 of the upper arm 50a, which is the opposite arm, to form a circuit equivalent to Fig. 4(B).

[0021] In the first embodiment, when the control unit 70 detects a short-circuit failure in any of the switching elements 51, 52, 53 of the upper arm 50a of the inverter 50, the control unit 70 outputs a control signal to turn on all of the switching elements 51, 52, 53 of the upper arm 50a, which is the arm on the same side, to form a circuit equivalent to the circuit in Fig. 4(B). When the control unit 70 detects a short-circuit failure in any of the switching elements 54, 55, 56 of the lower arm 50b of the inverter 50, the control unit 70 outputs a control signal to turn on all of the switching elements 54, 55, 56 of the lower arm 50b, which is the arm on the same side, to form a circuit equivalent to the circuit in Fig. 4(A).

[0022] This makes it possible to suppress the regenerative voltage generated when the motor 30 is forcibly rotated to be equal to or lower than the withstand voltage of the inverter 50, and prevents the regenerative voltage from being applied to the DC power supply 10 and the smoothing capacitor 21 connected between the terminals of the DC power supply 10. It is also possible to reduce the risk of an excessive demagnetizing current flowing to the motor 30 due to an unexpected short circuit path or open state, or of a voltage exceeding the withstand voltage being applied to the DC power supply 10, which could lead to a circuit malfunction.

[0023] <Operation of the First Embodiment> FIG. 5 is a diagram showing an example of a path of a regenerative current in the case where an open circuit fault occurs in the switching element 54 of the lower arm 50b of the inverter 50 in FIG. 1 due to some cause by using a thick line. FIG. 6 is a waveform diagram showing an example of a DC voltage Vdc [V], d-axis and q-axis currents IdR and IqR [A], phase currents Iu, Iv, and Iw [A], and a rotation speed [rpm] of the motor 30 in the case where an open circuit fault occurs in FIG. 5. In this case, as shown in FIG. 5 and FIG. 6, due to the open state of the switching element 54, the current that normally flows through the switching elements 54, 55, and 56 flows into the motor 30 only through the free wheel diode 54a. At this time, as shown in FIG. 6, the phase current flowing into the motor 30 becomes excessive, which may demagnetize the permanent magnet of the motor 30.

[0024] FIG. 7 is a schematic diagram of the inverter 50 of FIG. under Arm 50b FIG. 8 is a diagram showing an example of a path of a regenerative current when an open fault occurs in the switching element 54 and the free wheel diode 54a of FIG. 7, with a thick line. FIG. 8 is a waveform diagram showing an example of a DC voltage Vdc [V], d-axis and q-axis currents IdR and IqR [A], phase currents Iu, Iv, and Iw [A], and a rotation speed [rpm] of the motor 30 when an open fault occurs in FIG. 7. In this case, if all of the switching elements 54, 55, and 56 of the lower arm 50b are turned on, a current path shown by a thick line in FIG. 7 is formed. Due to the open state of the switching element 54 and the free wheel diode 54a of the lower arm 50b, the regenerative current that should be originally confined in the lower arm 50b flows to the DC power source 10 side through the free wheel diode 51a of the upper arm 50a. As a result, a DC voltage is applied to the DC power source 10, and the regenerative voltage cannot be suppressed. In addition, a negative voltage is generated across the switching element 54 and the freewheeling diode 54a that have an open circuit fault, and if this voltage exceeds the absolute maximum rating, it may cause the inverter 50 to malfunction. The negative voltage referred to here indicates the voltage across the switching element that is generated due to an open circuit fault, and is a voltage that is very large compared to the voltage drop caused by the characteristics of the element, such as the ON voltage of the switching element. As shown in FIG. 8, the DC voltage Id applied to the DC power supply 10 c increases gradually over time.

[0025] <Operation when inverter failure is detected> 9 is a flowchart showing failure detection and operation of the inverter 50 of the motor drive device 1. First, in step S1, the control unit 70 operates under the condition that the bus voltage detected by the DC voltage detection unit 40 is equal to or higher than the control power supply operating voltage that enables the operation of the control unit 70 and is equal to or lower than the withstand voltage of the smoothing capacitor 21.

[0026] In the next step S2, the control unit 70 detects whether or not there is a failure in the switching elements 51 to 56 and the free wheel diodes 51a to 56a that constitute the inverter 50. If no failure is detected in step S2, lineIf the voltage is greater than a predetermined threshold Vth (step S8), the switching elements 51, 52, and 53 of the upper arm 50a are short-circuited (ON) (step S9). If there is no failure and the bus voltage is greater than the threshold, either the upper arm or the lower arm may be short-circuited (ON).

[0027] In the next step S2, the control unit 70 detects a failure in the switching elements 51 to 56 and the free wheel diodes 51a to 56a that constitute the inverter 50. However, in step S3, an open circuit failure is not detected in the upper arm 50a (i.e., it is presumed that a failure exists in the lower arm 50b). line If the voltage is greater than the threshold value Vth (step S6), the switching elements 51, 52, and 53 of the upper arm 50a are shorted (turned on) (step S7).

[0028] In the next step S3, the control unit 70 detects an open circuit fault in the upper arm 50a and line If the voltage is greater than the threshold Vth (step S4), the switching elements 54, 55, and 56 of the lower arm 50b are shorted (turned on) (step S5).

[0029] 10(A) and (B), 11(A) and (B), and 12(A) and (B) are circuit diagrams in which the current path when fault detection is performed is indicated by a thick line. First, as shown in FIG. 10(A), switching elements 51 and 54 are simultaneously turned on, and other switching elements are turned off. When switching elements 51 and 54 are normal, as shown in FIG. 10(A), switching elements 51 and 54 are turned on, and a short-circuit current flows from DC power supply 10. However, when either switching element 51 or 54 has an open circuit fault, no short-circuit current flows, and it is found that either switching element 51 or 54 has an open circuit fault.

[0030] 10B, switching elements 51 and 55 (or 56) are simultaneously turned on, and the other switching elements are turned off. When switching element 51 is normal, a current flows from the DC voltage through the windings of motor 30, but when an open circuit fault occurs, no current flows.

[0031] 11(A), switching elements 52 and 55 are simultaneously turned on. When switching elements 52 and 55 are normal, switching elements 52 and 55 are conductive and a short-circuit current flows from DC power supply 10. However, when switching elements 52 and 55 have an open circuit fault, no short-circuit current flows, and it is found that either switching element 52 or 55 has an open circuit fault.

[0032] Next, as shown in FIG. 11B, the switching elements 52 and 56 (or the switching elements 52 and 54) are simultaneously turned on. When the switching element 52 is normal, a current flows from the DC power supply 10 through the windings of the motor 30, but when an open fault occurs, no current flows.

[0033] 12(A), switching elements 53 and 56 are simultaneously turned on. When switching elements 53 and 56 are normal, switching elements 53 and 56 are conductive and a short-circuit current flows from DC power supply 10. However, when either switching element 53 or 56 has an open circuit fault, no short-circuit current flows, indicating that either switching element has an open circuit fault.

[0034] 12(B), switching elements 53 and 54 (or 55) are simultaneously turned on. When switching element 53 is normal, a current flows from DC power supply 10 through the winding of motor 30, and when an open fault occurs, no current flows.

[0035] In this way, by controlling the switching elements 51 to 56 to operate in such a way as to identify the fault location and configuring the device to be capable of detecting the current that flows at that time, it is possible to identify the location of the faulty switching element (i.e., the fault location).

[0036] Another method is to use a charging current that flows from the motor 30 to the DC power supply 10 when a regenerative voltage is generated. For example, the regenerative voltage generated in the motor 30 flows as a current through a path that runs from the switching element 51 via the DC power supply 10, through the switching element 55 or the switching element 56, and back to the motor 30. However, if the switching element 51 has an open circuit fault, no current flows through this path. In this way, if no current flows at the timing when it should, it is possible to determine that the switching elements 51, 52, and 53 of the inverter 50 have a fault.

[0037] It is desirable to perform this failure detection operation when the regenerative voltage from the motor 30 is low, i.e., when the number of revolutions (rotation speed) is low. When the regenerative voltage from the motor 30 is high and a switching element has an open circuit fault, an excessive negative voltage is generated between the switching elements that have had an open circuit fault. For example, if there is a peripheral circuit for driving the switching elements, there is a risk of malfunction due to the influence of the negative voltage. For this reason, it is desirable to perform failure detection when the regenerative voltage is low and the negative voltage is low. knowledge However, it is recommended to use a DC power source of 10 DC power from When no DC current is supplied, the regenerative voltage of the motor 30 generates a DC current. electric power In order to operate the fault detection unit, the DC power supply 10 To Generated by Control power Therefore, a certain amount of regenerative voltage must be supplied. electric power The control voltage obtained by force Then, when an open-circuit fault in a switching element is detected, the three-phase switching element in the arm without the fault is turned on, thereby making it possible to prevent a fault due to a negative voltage.

[0038] As a result, even if an open circuit fault occurs in a switching element constituting the inverter 50, it is possible to expect an effect of suppressing the regenerative voltage. Note that the operation according to the above-described flowchart is merely an example, and any method of suppressing the regenerative voltage so as not to cause the control unit 70 to short-circuit the arm on the faulty side may be used, and is not limited to this.

[0039] As a result, even when an element has an open circuit failure, it is possible to suppress the regenerative voltage, prevent demagnetization of the motor 30 and application of a DC voltage exceeding the withstand voltage, and obtain a highly reliable motor drive device.

[0040] 13 is a flowchart showing fault detection and operation of the inverter 50 of the motor drive device 1. First, in step S1, the control unit 70 operates under the condition that the bus voltage detected by the DC voltage detection unit 40 is equal to or higher than the control power supply operating voltage that enables the operation of the control unit 70 and is equal to or lower than the withstand voltage of the smoothing capacitor 21.

[0041] In the next step S2, the control unit 70 detects whether or not there is a failure in the switching elements 51 to 56 and the free wheel diodes 51a to 56a that constitute the inverter 50. If no failure is detected in step S2, line If the voltage is greater than a predetermined threshold Vth (step S26), the switching elements 54, 55, and 56 of the lower arm 50b are short-circuited (ON) (step S27). If there is no failure and the bus voltage is greater than the threshold, either the upper arm or the lower arm may be short-circuited (ON).

[0042] In the next step S2, the control unit 70 detects a failure in the switching elements 51 to 56 and the free wheel diodes 51a to 56a that configure the inverter 50. But Step S2 1 In the above, no short circuit fault is detected in the upper arm 50a (i.e., it is assumed that there is a fault in the lower arm 50b), and lineIf the voltage is greater than the threshold value Vth (step S24), the switching elements 54, 55, and 56 of the lower arm 50b are shorted (turned on) (step S25).

[0043] In the next step S21, the control unit 70 controls the upper arm 50a Short circuit A fault is detected and the mother line If the voltage is greater than the threshold value Vth (step S22), the switching elements 51, 52, and 53 of the upper arm 50a are shorted (turned on) (step S23).

[0044] As shown in FIG. 2, the switching elements 51 to 56 of the inverter 50 are IGBTs, but may be other switching elements such as metal-oxide-semiconductor field-effect transistors (MOSFETs).

[0045] In addition, as shown in FIG. 2, the inverter 50 is a three-phase bridge circuit, but in the case of a two-phase circuit or a circuit composed of multiple bridge circuits, the same effect can be obtained by inputting a control signal to the control unit 70 so as to perform short-circuit and open-circuit operations.

[0046] Furthermore, the control unit 70 is electric power However, if the regenerative voltage generated when the motor 30 is forcibly rotated reaches a predetermined value or more, the same effect as when power is supplied from the DC power supply 10 can be obtained, and operation becomes possible.

[0047] Effects of the First Embodiment In the motor drive device 1 according to the first embodiment, circuit malfunctions due to the occurrence of unexpected open states and short circuits caused by element failures can be prevented at low cost without increasing the number of parts. This makes it possible to use a permanent magnet synchronous motor with a large induced voltage constant as the motor 30. In addition, this has the effect of reducing losses in the motor drive device 1, contributing to energy conservation, and making it possible to mitigate global warming.

[0048] Second Embodiment Fig. 14 is a diagram illustrating a schematic configuration of a motor drive device 2 according to a second embodiment. In Fig. 14, components that are the same as or correspond to those shown in Fig. 1 are given the same reference numerals as those shown in Fig. 1. The motor drive device 2 according to the second embodiment differs from the motor drive device 1 according to the first embodiment in that it has an AC voltage detection unit 41 that detects the AC voltage on the output side of the inverter 50, and a control unit 71 controls the inverter 50 based on the AC voltage detection value detected by the AC voltage detection unit 41. The other components of the second embodiment are the same as those of the first embodiment.

[0049] That is, the second embodiment differs from the first embodiment in that the physical quantity input to the control unit 71 is changed from a DC voltage to an AC voltage, and the predetermined threshold value becomes the threshold value for the AC voltage value. In the motor drive device 2 according to the second embodiment, it is possible to prevent circuit malfunctions due to the occurrence of unexpected open states and short circuits caused by element failures at low cost and without increasing the number of components.

[0050] Third Embodiment Fig. 15 is a diagram illustrating a schematic configuration of a motor drive device 3 according to embodiment 3. In Fig. 15, components that are the same as or correspond to those shown in Fig. 1 are given the same reference numerals as those shown in Fig. 1. The motor drive device 3 according to embodiment 3 differs from the motor drive device 1 according to embodiment 1 in that it has a rotation speed detection unit 42 that detects the rotation speed of the motor 30, and a control unit 72 controls the inverter 50 based on the rotation speed [rpm] detected by the rotation speed detection unit 42. Other configurations of embodiment 3 are the same as those of embodiment 1.

[0051] That is, the third embodiment differs from the first embodiment in that the physical quantity input to the control unit 72 is converted from a DC voltage to a rotation speed, and a predetermined threshold value is the threshold value of the rotation speed. In the motor drive device 3 according to the third embodiment, it is possible to prevent circuit malfunctions due to the occurrence of unexpected open states and short circuits caused by element failures at low cost without increasing the number of components.

[0052] Fourth Embodiment 16 is a diagram showing the configuration of an air conditioner 4 as a refrigeration cycle device according to embodiment 4. The air conditioner 4 has a motor drive device 1 and a refrigeration cycle device 200. The air conditioner 4 is, for example, an air conditioner or a refrigerator. The motor drive device 1 may be replaced with motor drive device 2 or 3.

[0053] The refrigeration cycle device 200 includes a compressor 201, a four-way valve 202, an internal heat exchanger 203, an expansion mechanism 204, a heat exchanger 205, and refrigerant piping 206 that sequentially connects these components. Inside the compressor 201, there are provided a compression mechanism 207 that compresses the refrigerant, and a motor 208 (for example, the motor 30 in the first to third embodiments) that operates the compression mechanism 207. The motor 208 is driven by an inverter 50 of any one of the motor drive devices 1 to 3.

[0054] In the air conditioner 4 according to the fourth embodiment, unexpected open states due to element failures and circuit malfunctions due to the occurrence of short circuits can be prevented at low cost without increasing the number of parts. This reduces losses in the motor drive device 1, contributing to energy conservation and helping to mitigate global warming.

[0055] <<Variation>> The control unit 7 in the above-mentioned embodiments 1 to 3 0 The control units 70, 71, and 72 may be configured with a CPU (Central Processing Unit), a DSP (Digital Signal Processor), a microcomputer, etc. For example, the control units 70, 71, and 72 may be control circuits configured with electric circuits such as analog circuits or digital circuits.

[0056] The motor driving devices 1, 2, and 3 according to the above-mentioned first, second, and third embodiments are applicable to ventilation fans, washing machines, vehicles such as automobiles, and the like. [Explanation of symbols]

[0057] 1, 2, 3 motor drive device, 4 air conditioner (refrigeration cycle application device), 10 DC power supply, 30 motor (permanent magnet synchronous motor), 40 DC voltage detection unit, 41 AC voltage detection unit, 42 rotation speed detection unit, 50 inverter, 50a upper arm, 50b lower arm, 51, 52, 53 switching element (first switching element), 54, 55, 56 switching element (second switching element), 51a, 52a, 53a freewheel diode (first freewheel diode), 54a, 55a, 56a freewheel diode (second freewheel diode), 70, 71, 72 control unit.

Claims

1. An inverter that receives a DC voltage from a DC power supply and outputs a voltage to a motor; a control unit that detects a fault in the inverter and controls the inverter based on the detected fault; having The inverter is a plurality of first switching elements of an upper arm connected between a positive side of the DC power supply and the motor, and a plurality of first freewheeling diodes connected in parallel to the plurality of first switching elements, respectively; a plurality of second switching elements of a lower arm connected between a negative side of the DC power supply and the motor, and a plurality of second freewheeling diodes connected in parallel to the plurality of second switching elements, respectively; having During a period in which all of the first switching elements and all of the second switching elements are controlled to an off state in order to stop driving of the motor, the control unit A control operation is executed to output a control signal for turning on all of the plurality of second switching elements of the lower arm when an open-circuit failure of any of the first switching elements of the upper arm of the inverter is detected, and to output a control signal for turning on all of the plurality of first switching elements of the upper arm when an open-circuit failure of any of the second switching elements of the lower arm of the inverter is detected. Motor drive device.

2. an inverter that receives a DC voltage from a DC power supply and generates a voltage that is output to a motor; a control unit that detects a fault in the inverter and controls the inverter based on the detected fault; having The inverter is a plurality of first switching elements of an upper arm connected between a positive side of the DC power supply and the motor, and a plurality of first freewheeling diodes connected in parallel to the plurality of first switching elements, respectively; a plurality of second switching elements of a lower arm connected between a negative side of the DC power supply and the motor, and a plurality of second freewheeling diodes connected in parallel to the plurality of second switching elements, respectively; having During a period in which all of the first switching elements and all of the second switching elements are controlled to an off state in order to stop driving of the motor, the control unit When a short-circuit failure of any first switching element of the upper arm of the inverter is detected, a control signal is output to turn on all of the plurality of first switching elements of the upper arm, and when a short-circuit failure of any second switching element of the lower arm of the inverter is detected, a control operation is output to turn on all of the plurality of second switching elements of the lower arm. Motor drive device.

3. During a period in which all of the first switching elements and all of the second switching elements are controlled to an off state in order to stop driving of the motor, the control unit When a short-circuit failure of any first switching element of the upper arm of the inverter is detected, a control signal is output to turn on all of the plurality of first switching elements of the upper arm, and when a short-circuit failure of any second switching element of the lower arm of the inverter is detected, a control operation is output to turn on all of the plurality of second switching elements of the lower arm. The motor drive device according to claim 1 .

4. The control unit receives a regenerative voltage generated by the motor, The control unit executes the control operation using the regenerative voltage. The motor drive device according to any one of claims 1 to 3.

5. A DC voltage detection unit detects a voltage on the input side of the inverter and outputs a voltage detection signal. The control unit controls the inverter based on the voltage detection signal. The motor drive device according to any one of claims 1 to 4.

6. Further, an AC voltage detection unit detects a voltage on the output side of the inverter and outputs a voltage detection signal, The control unit controls the inverter based on the voltage detection signal. The motor drive device according to any one of claims 1 to 4.

7. A rotation speed detection unit detects the rotation speed of the motor and outputs a rotation speed signal, The control unit controls the inverter based on the rotation speed signal. The motor drive device according to any one of claims 1 to 4.

8. A motor drive device according to any one of claims 1 to 7; a refrigeration cycle device having a motor driven by the motor drive device; Refrigeration cycle application equipment having the above structure.

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