Fault detection device for detecting fault of parallel-driven switch and motor drive device

Abstract

A fault detection device and a motor drive device having the fault detection device are provided, wherein the fault detection device detects a fault of a switch in a circuit in which a plurality of switches connected in parallel are provided on a current path and the plurality of switches are driven in parallel to prevent abnormal overheating. The fault detection device (1) detects a fault of a switch (21-1 to 21-n) that selectively switches between conduction and non-conduction on a current path (50), and comprises: at least two temperature sensors (11 to 11-m), the temperature sensors (11-1 to 11-m) having a resistance value between terminals that changes according to temperature, and are arranged near at least two switches (21-1 to 21-n) connected in parallel to each other and are electrically connected in series to each other; a detection unit (12) that detects a combined resistance value of the at least two temperature sensors (11 to 11-m); and a determination unit (13) that determines that at least one of the at least two switches (21-1 to 21-n) has a fault based on the combined resistance value.

Description

Technical Field

[0001] The present invention relates to a fault detection device for detecting faults of switches driven in parallel and a motor drive device. Background Art

[0002] As switches that selectively switch between conduction (also called "closed" or "on") and non-conduction (also called "open" or "off") on a current path, relays, semiconductor switching elements, and electromagnetic contactors are used. In the case where it is desired to use a switch with a small rated current to switch between conduction and non-conduction of a current path through which a large current flows, a plurality of switches are connected in parallel and driven in parallel. In such parallel driving, a large current is dispersedly passed through each switch by closing a plurality of switches connected in parallel at the same time, and a large current is cut off by opening a plurality of switches connected in parallel at the same time.

[0003] For example, there is known a power conversion device that outputs variable-voltage and variable-frequency AC power, characterized in that it comprises: a forward converter that rectifies the AC voltage of an AC power source and converts it into a DC voltage; a DC intermediate circuit that has a smoothing capacitor that smoothes the DC voltage of the forward converter; a current limiting circuit that suppresses the charging current to the smoothing capacitor of the DC intermediate circuit; a voltage detection circuit that detects the voltage of the DC intermediate circuit; an inverse converter that converts the DC voltage of the forward converter into an AC voltage; n temperature detection elements that detect the temperatures of each of the n relays of a circuit substrate that is arranged at terminals corresponding to the contact portions of n relays connected in parallel with a resistor of the current limiting circuit; and a control unit that detects which of the n relays is abnormal based on the detection results of each temperature detection element (for example, refer to patent document 1).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 5743944 Summary of the invention

[0007] Problems to be solved by the invention

[0008] In a circuit that switches between conduction (closed) and non-conduction (open) on a current path by driving a plurality of switches connected in parallel in parallel, if a fault occurs in which at least one switch is not closed and remains open (hereinafter referred to as an "open circuit fault") despite instructions for closing all switches, current concentrates on the switch that is normally closed according to the closing instruction, causing abnormal overheating. Due to abnormal overheating caused by the open circuit fault, a normal switch, a substrate on which the switch is provided, and various electronic components located near the switch may sometimes be damaged. Therefore, it is desirable to detect switch faults in a circuit in which a plurality of switches connected in parallel are provided on a current path and these plurality of switches are driven in parallel to prevent abnormal overheating.

[0009] Means for solving problems

[0010] According to one embodiment of the present disclosure, a fault detection device for detecting a fault of a switch that selectively switches between conduction and non-conduction on a current path comprises: at least two temperature sensors, which are temperature sensors whose resistance value between terminals changes according to temperature changes, and are arranged near at least two switches connected in parallel to each other and are electrically connected in series with each other; a detection unit, which detects the combined resistance value of the at least two temperature sensors; and a determination unit, which determines that a fault has occurred in at least one of the at least two switches based on the combined resistance value.

[0011] In addition, according to one embodiment of the present disclosure, a motor drive device includes: the above-mentioned fault detection device; a converter circuit, which converts AC power input from an AC power supply into DC power and outputs it; a DC link capacitor, which is arranged in a DC link as a DC output side of the converter circuit; an inverter circuit, which converts DC power in the DC link into AC power for motor driving and outputs it; and a pre-charging circuit, which has a switch and a pre-charging resistor connected in parallel with the switch, for preventing an inrush current during pre-charging of the DC link capacitor.

[0012] Effects of the Invention

[0013] According to one embodiment of the present disclosure, a fault detection device and a motor drive device having the fault detection device can be realized, wherein the fault detection device detects a fault of a switch in a circuit in which a plurality of switches connected in parallel are arranged on a current path and driven in parallel to prevent abnormal overheating. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a diagram showing a fault detection device according to one embodiment of the present disclosure.

[0015] Figure 2AThis is a diagram illustrating the flow of current in a circuit in which a plurality of switches connected in parallel are provided on a current path in one embodiment of the present disclosure, and shows a case where all switches normally perform closing operations in response to closing commands.

[0016] Figure 2B This is a diagram illustrating the flow of current in a circuit in which a plurality of switches connected in parallel are provided on a current path in one embodiment of the present disclosure, and shows a case where an open circuit failure occurs in one switch despite a closing command.

[0017] Figure 3 It is a graph illustrating the resistance-temperature characteristics of a PTC thermistor.

[0018] Figure 4 This is a flowchart showing the operation flow of the fault detection device according to the first embodiment using a PTC thermistor as a temperature sensor.

[0019] Figure 5 It is a graph illustrating the resistance-temperature characteristics of an NTC thermistor.

[0020] Figure 6 This is a flowchart showing the operation flow of the fault detection device according to the second embodiment using an NTC thermistor as a temperature sensor.

[0021] Figure 7 This is a perspective view illustrating a pre-charging circuit provided with a temperature sensor in a fault detection device according to an embodiment of the present disclosure.

[0022] Figure 8 This is a circuit diagram illustrating a precharge circuit provided with a temperature sensor in a fault detection device according to an embodiment of the present disclosure.

[0023] Fig. 9 This is a diagram illustrating a motor drive device including a fault detection device according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0024] Hereinafter, a fault detection device and a motor drive device for detecting a fault of a switch driven in parallel will be described with reference to the accompanying drawings. For ease of understanding, the scales of these drawings are appropriately changed. The method shown in the accompanying drawings is an example for implementation and is not limited to the illustrated embodiment.

[0025] Figure 1 It is a diagram showing a fault detection device according to one embodiment of the present disclosure.

[0026] A fault detection device 1 according to an embodiment of the present disclosure detects a fault in at least one of the multiple switches 21-1 to 21-n in a circuit in which multiple switches 21-1 to 21-n connected in parallel are arranged on a current path 50 and these multiple switches 21-1 to 21-n (where n is an integer greater than or equal to 2) are driven in parallel.

[0027] The switches 21-1 to 21-n, which are the fault detection objects of the fault detection device 1, selectively switch between conduction and non-conduction on the current path 50. For each of the switches 21-1 to 21-n, even if the rated current is small, by connecting these switches 21-1 to 21-n in parallel with each other and driving them in parallel, it is possible to achieve selective switching between conduction (closed) and non-conduction (open) in the current path 50 where a large current flows. That is, by closing a plurality of switches connected in parallel at the same time, a large current can be dispersedly flowed through each switch, and by opening a plurality of switches connected in parallel at the same time, a large current can be cut off. In addition, in Figure 1 In the figure, the control unit which instructs the switches 21 - 1 to 21 - n to close and turn on is omitted from the figure.

[0028] Examples of switches 21-1 to 21-n that are the fault detection targets of the fault detection device 1 include relays, semiconductor switch elements, and electromagnetic contactors. Examples of semiconductor switch elements include FETs, IGBTs, thyristors, GTOs, and transistors.

[0029] In addition, as an example of a circuit having switches 21-1 to 21-n as fault detection targets of the fault detection device 1, there is a pre-charging circuit provided in a motor drive device. The details will be described later, and the pre-charging circuit prevents the inrush current that may be generated when pre-charging the DC link capacitor between the DC output side of the converter circuit and the DC input side of the inverter circuit provided in the motor drive device. The pre-charging circuit has a switch and a pre-charging resistor connected in parallel with the switch. After the pre-charging is completed, the switch is closed and a large current flows, so sometimes a response is taken by connecting a plurality of switches in parallel and driving them in parallel. The fault detection device 1 of one embodiment of the present disclosure can be used for fault detection of a plurality of switches in a pre-charging circuit having such a plurality of switches driven in parallel. Alternatively, the fault detection device 1 can also be used for fault detection of a plurality of switches provided in a power braking circuit, a converter circuit, or an inverter circuit.

[0030] A fault detection device 1 according to an embodiment of the present disclosure includes at least two temperature sensors 11 - 1 to 11 - m (where m is an integer equal to or greater than 2), a detection unit 12 , and a determination unit 13 .

[0031] The temperature sensors 11-1 to 11-m are elements whose resistance value between terminals changes with temperature. Examples of the temperature sensors 11-1 to 11-m include PTC thermistors whose resistance value increases with temperature rise and NTC thermistors whose resistance value decreases with temperature rise.

[0032] The temperature sensors 11-1 to 11-m are arranged near the switches 21-1 to 21-n on a substrate on which at least two switches 21-1 to 21-n connected in parallel are mounted. The number m of the temperature sensors 11-1 to 11-m is equal to or less than the number n of the switches 21-1 to 21-n. The temperature sensors 11-1 to 11-m are electrically connected in series with each other. Therefore, the combined resistance value of the temperature sensors 11-1 to 11-m connected in series with each other changes according to the temperature change of the substrate near the switches 21-1 to 21-n on which the switches 21-1 to 21-n are mounted.

[0033] The detection unit 12 detects the combined resistance value of the temperature sensors 11-1 to 11-m. For example, when m temperature sensors are electrically connected in series in the order of the first temperature sensor 11-1, ..., the mth temperature sensor 11-m (where m is an integer greater than 2), the total resistance value between the terminal on the side not connected to the second temperature sensor of the two terminals of the first temperature sensor 11-1 and the terminal on the side not connected to the m-1th temperature sensor 11-m+1 of the two terminals of the mth temperature sensor 11-m is the combined resistance value.

[0034] When the resistance values ​​of the temperature sensors 11 - 1 to 11 - m are respectively R1 to Rm, the detection unit 12 calculates the combined resistance value R according to Formula 1, for example. A .

[0035] [Mathematical formula 1]

[0036]

[0037] The determination unit 13 determines that at least one of the switches has a fault based on the combined resistance value detected by the detection unit 12. Details of the determination process of the determination unit 13 will be described later.

[0038] The detection unit 12 and the determination unit 13 may be composed of a combination of an analog circuit and an operation processing device, or may be composed of only an analog circuit, or may be composed of only an operation processing device. The operation processing device includes, for example, concepts such as IC, LSI, CPU, MPU, DSP, etc. For example, the operation processing device may also operate according to a software program that realizes the functions of the detection unit 12 and / or the determination unit 13. In addition, for example, the detection unit 12 may be composed of a comparator, and the determination unit 13 may be composed of an LSI. In addition, for example, the detection unit 12 and the determination unit 13 may be combined and composed of one LSI.

[0039] Figure 2A This is a diagram illustrating the flow of current in a circuit in which a plurality of switches connected in parallel are provided on a current path in one embodiment of the present disclosure, and shows a case where all switches normally perform closing operations in response to closing commands. Figure 2B This is a diagram illustrating the flow of current in a circuit in which a plurality of switches connected in parallel are provided on a current path in one embodiment of the present disclosure, and shows a case where an open circuit failure occurs in one switch despite a closing command.

[0040] like Figure 2A As shown, when all switches 21-1 to 21-n are normal, switches 21-1 to 21-n are all closed (conducted) in response to the closing command. As a result, the current flowing in the current path 50 flows through the switches 21-1 to 21-n in a dispersed manner, so that the temperature change of the substrate near the switches 21-1 to 21-n and the substrate on which these switches 21-1 to 21-n are mounted is small. Therefore, the change of the resistance value of each of the temperature sensors 11-1 to 11-m is also small, and therefore, the change of the combined resistance value detected by the detection unit 12 is also small.

[0041] like Figure 2B As shown, although all switches 21-1 to 21-n are instructed to close, in the event of an open circuit fault in which switch 21-2 does not close but remains open, for example, switch 21-2 is in a non-conducting state in which no current flows, and therefore the flow of current is concentrated on normal switches other than switch 21-2 (i.e., switches in a conductive state). As a result, the temperature change around the normal switches other than switch 21-2 and around the substrate on which the normal switches are mounted becomes larger. Therefore, the change in the resistance value of each of the temperature sensors 11-1 to 11-m that are arranged near the normal switches becomes larger, and therefore, the change in the combined resistance value detected by the detection unit 12 also becomes larger. Figure 2BAs an example, an open circuit fault is assumed to occur in one switch 21-2. However, if an open circuit fault occurs in multiple switches, the flow of current is further concentrated on normal switches other than the normal switches. Therefore, the temperature change near the normal switches becomes larger, and the change in the resistance value of each temperature sensor arranged near the normal switches also becomes larger. Along with this, the change in the combined resistance value detected by the detection unit 12 also becomes larger.

[0042] Thus, when some of the switches 21-1 to 21-n have an open circuit failure, the combined resistance value detected by the detection unit 12 changes significantly from the normal value. Therefore, the determination unit 13 compares the combined resistance value detected by the detection unit 12 with a predetermined threshold value, and determines whether at least one of the switches 21-1 to 21-n has a failure based on the comparison result.

[0043] The determination process of the determination unit 13 differs depending on whether the temperature sensors 11-1 to 11-m are PTC thermistors or NTC thermistors. Next, the details of the determination process of the determination unit 13 are described separately in a first mode in which the temperature sensors 11-1 to 11-m are PTC thermistors and a second mode in which the temperature sensors 11-1 to 11-m are NTC thermistors.

[0044] First, a first embodiment in which a PTC thermistor is used for each of the temperature sensors 11 - 1 to 11 - m in the fault detection device 1 according to one embodiment of the present disclosure will be described.

[0045] Figure 3 It is a graph illustrating the resistance-temperature characteristics of a PTC thermistor.

[0046] PTC thermistor is a thermistor with a specific Curie temperature T Q At low temperatures, the resistance value is roughly constant. When the Curie temperature T is exceeded, the resistance value is Q When multiple PTC thermistors are electrically connected in series, only the temperature near at least one PTC thermistor exceeds the Curie temperature T Q , the combined resistance value of the PTC thermistors connected in series increases dramatically. Figure 3 The resistance-temperature characteristic shown shows the relationship between the temperature and the resistance value of a single PTC thermistor, and can be understood to show the relationship between the temperature and the combined resistance value of a plurality of PTC thermistors connected in series.

[0047] In the first embodiment in which each of the temperature sensors 11-1 to 11-m in the fault detection device 1 of one embodiment of the present disclosure uses a PTC thermistor, the threshold value to be compared with the combined resistance value of the temperature sensors 11-1 to 11-m in the determination process of the determination unit 13 may be set as follows. Hereinafter, the threshold value used in the determination process of the determination unit 13 in the first embodiment is referred to as the "first threshold value".

[0048] In the first embodiment, the PTC thermistors serving as the temperature sensors 11-1 to 11-m are selected to have a Curie temperature T lower than the temperature at which a failure is determined to occur (i.e., the temperature at which abnormal overheating occurs). Q PTC thermistor. Each of the temperature sensors 11-1 to 11-m is preferably composed of a PTC thermistor having the same temperature resistance value characteristic. The "temperature at which a fault is determined to occur" can be selected by considering, for example, the heat resistance temperature of the switches 21-1 to 21-n, the heat resistance temperature of the substrate on which the switches 21-1 to 21-n are mounted, the heat resistance temperature of various components arranged near the switches 21-1 to 21-n, and the heat resistance temperature of the substrate on which the switches 21-1 to 21-n and various components are mounted. As described above, the temperature change near the normal switches other than the switches associated with the open circuit fault and around the substrate on which the normal switches are mounted becomes larger, and therefore, the resistance value of the PTC thermistor arranged near the normal switch increases sharply. When the resistance value of the PTC thermistor near the normal switch increases sharply, of course, the combined resistance value of the PTC thermistors connected in series also increases sharply. In the first method, the Curie temperature T of one PTC thermistor is set to 0.050°C in consideration of safety. Q The resistance value obtained by adding a small margin to the corresponding resistance value is set as the first threshold value R th1 The determination unit 13 determines the value of the first threshold value R th1 The comparison result with the combined resistance value detected by the detection unit 12 determines whether an open circuit fault has occurred. That is, the determination unit 13 determines whether an open circuit fault has occurred when the combined resistance value of the PTC thermistors (temperature sensors 11-1 to 11-m) connected in series exceeds the first threshold value R th1 In the case of , it is determined that an open circuit failure has occurred, which causes a sudden increase in the combined resistance value of the PTC thermistor (temperature sensors 11-1 to 11-m). th1 It may be stored in a rewritable storage unit (not shown) and rewritable by an external device, thereby even if the first threshold value R is temporarily set. th1 Afterwards, it can be changed to an appropriate value as needed.

[0049] Figure 4 This is a flowchart showing the operation flow of the fault detection device according to the first embodiment using a PTC thermistor as a temperature sensor.

[0050] exist Figure 1 In the circuit in which the plurality of switches 21-1 to 21-n connected in parallel are provided on the current path 50 and driven in parallel, in step S101, the detection unit 12 detects the combined resistance value of the temperature sensors 11-1 to 11-m respectively constituted by PTC thermistors. Data related to the combined resistance value detected by the detection unit 12 is transmitted to the determination unit 13.

[0051] In step S102, the determination unit 13 compares the combined resistance value detected by the detection unit 12 with the first threshold value R th1 Compare and determine whether the combined resistance value exceeds the first threshold R th1 In step S102, when it is determined that the combined resistance value exceeds the first threshold value R th1 If the combined resistance value is not determined to exceed the first threshold value R th1 In the case of , the process returns to step S101. The processes of steps S101 and S102 are repeatedly executed in a predetermined cycle.

[0052] In step S102, it is determined that the combined resistance value exceeds the first threshold value R th1 In the case of the above, in step S103, the determination unit 13 determines that at least one of the switches 21-1 to 21-n has failed.

[0053] Next, a second embodiment in which an NTC thermistor is used for each of the temperature sensors 11 - 1 to 11 - m in the fault detection device 1 according to the embodiment of the present disclosure will be described.

[0054] Figure 5 It is a graph illustrating the resistance-temperature characteristics of an NTC thermistor.

[0055] NTC thermistors are elements whose resistance value decreases as the temperature rises. When a plurality of NTC thermistors are electrically connected in series, if the temperature near at least one NTC thermistor rises, the combined resistance value of the NTC thermistors connected in series decreases. Figure 5 The resistance-temperature characteristic shown shows the relationship between the temperature and the combined resistance value of a plurality of NTC thermistors connected in series.

[0056] In the second embodiment in which each of the temperature sensors 11-1 to 11-m in the fault detection device 1 of one embodiment of the present disclosure uses an NTC thermistor, the threshold value to be compared with the combined resistance value of the temperature sensors 11-1 to 11-m in the determination process of the determination unit 13 may be set as follows. Hereinafter, the threshold value used in the determination process of the determination unit 13 in the second embodiment is referred to as the "second threshold value".

[0057] In order to realize the fault detection device 1 of one embodiment of the present disclosure by the temperature sensors 11-1 to 11-m composed of NTC thermistors, it is necessary to select NTC thermistors such that the combined resistance value of the plurality of NTC thermistors connected in series when at least one of the plurality of switches 21-1 to 21-n has an open circuit fault is smaller than the combined resistance value of the plurality of NTC thermistors connected in series when all the plurality of switches 21-1 to 21-n are normal. For example, if each of the temperature sensors 11-1 to 11-m is composed of NTC thermistors having the same temperature resistance value characteristic, it is easy to realize the fault detection device 1 that satisfies the relationship between the combined resistance value in the case of an open circuit fault and the combined resistance value in the normal state.

[0058] The more the number of NTC thermistors that reach the temperature determined as a failure (i.e., the temperature at abnormal overheating), the smaller the combined resistance value of the NTC thermistors (temperature sensors 11-1 to 11-m) connected in series. In the second method, for example, the heat resistance temperature of the switches 21-1 to 21-n, the heat resistance temperature of the substrate on which the switches 21-1 to 21-n are mounted, the heat resistance temperature of various components arranged near the switches 21-1 to 21-n, and the heat resistance temperature of the substrate on which the switches 21-1 to 21-n and various components are mounted are considered. For example, in consideration of safety, a resistance value obtained by adding a slight margin to the combined resistance value of the NTC thermistors (temperature sensors 11-1 to 11-m) connected in series when one NTC thermistor reaches the "temperature determined as a failure" is set as the second threshold value R. th2 The determination unit 13 determines the value of the second threshold value R th2 The comparison result with the combined resistance value detected by the detection unit 12 determines whether an open circuit fault has occurred. That is, the determination unit 13 determines whether an open circuit fault has occurred when the combined resistance value of the NTC thermistors (temperature sensors 11-1 to 11-m) connected in series is lower than the second threshold value R th2 In the case of , it is determined that at least an open circuit failure has occurred, which causes a decrease in the combined resistance value of the NTC thermistor (temperature sensors 11-1 to 11-m). th2 It may be stored in a rewritable storage unit (not shown) and rewritable by an external device, thereby even if the second threshold value R is temporarily set. th2 Afterwards, it can be changed to an appropriate value as needed.

[0059] Figure 6 This is a flowchart showing the operation flow of the fault detection device according to the second embodiment using an NTC thermistor as a temperature sensor.

[0060] exist Figure 1In the circuit shown in which the plurality of switches 21-1 to 21-n connected in parallel are provided on the current path 50 and driven in parallel, in step S201, the detection unit 12 detects the combined resistance value of the temperature sensors 11-1 to 11-m respectively constituted by NTC thermistors. Data on the combined resistance value detected by the detection unit 12 is sent to the determination unit 13.

[0061] In step S202, the determination unit 13 compares the combined resistance value detected by the detection unit 12 with the second threshold value R th2 Compare and determine whether the combined resistance value is lower than the second threshold R th2 In step S202, it is determined that the combined resistance value is lower than the second threshold value R th2 If the combined resistance value is not determined to be lower than the second threshold value R th2 In the case of , the process returns to step S201. The processes of steps S201 and S202 are repeatedly executed in a predetermined cycle.

[0062] In step S202, it is determined that the combined resistance value is lower than the second threshold value R th2 In the case of the above, in step S203, the determination unit 13 determines that at least one of the switches 21-1 to 21-n has failed.

[0063] In any one of the first and second modes described above, for example, the display unit may display the fault determination result of the determination unit 13. Examples of the display unit include a single display device, and a display device attached to a personal computer and a portable terminal. Alternatively, the fault determination result of the determination unit 13 may be output by an audio device that emits sound, such as voice, a speaker, a buzzer, a bell, etc. Thus, the operator can grasp that at least one of the switches 21-1 to 21-n has a fault. Therefore, the operator can take measures such as replacing or repairing the entire switches 21-1 to 21-n, or replacing or repairing the substrate or various components.

[0064] In any of the first and second aspects, the device having the device provided with Figure 1 The machine of the circuit of the plurality of switches 21-1 to 21-n connected in parallel as shown is stopped urgently or performs abnormality avoidance operation. In addition, the determination result of the determination unit 13 may be recorded in a storage device so that the determination result can be used later.

[0065] In addition, in the above-mentioned embodiment, the temperature sensors 11-1 to 11-m are electrically connected in series, the detection unit 12 detects the combined resistance value of the temperature sensors 11-1 to 11-m connected in series, and the determination unit 13 detects the occurrence of an open circuit fault based on the combined resistance value. As a variation of this, the temperature sensors 11-1 to 11-m may be connected in parallel to each other via respective terminals, and the detection unit 12 detects the combined resistance value of the temperature sensors 11-1 to 11-m connected in parallel. When the resistance values ​​of the temperature sensors 11-1 to 11-m connected in parallel are set to R1 to R2, the detection unit 12 may detect the combined resistance value of the temperature sensors 11-1 to 11-m connected in parallel. m When the detection unit 12 calculates the combined resistance value R according to Formula 2, for example B The determination unit 13 may also determine the value of the combined resistance R B To detect open circuit fault.

[0066] [Mathematical formula 2]

[0067]

[0068] Next, taking a pre-charging circuit as an example, an example of disposing a temperature sensor in a fault detection device according to an embodiment of the present disclosure is described.

[0069] Figure 7 1 is a perspective view illustrating a pre-charging circuit provided with a temperature sensor in a fault detection device according to an embodiment of the present disclosure. Figure 8 1 is a circuit diagram illustrating a precharge circuit provided with a temperature sensor in a fault detection device according to an embodiment of the present disclosure. Figure 7 and Figure 8 In the description, as an example, a case where two switches are provided in the precharge circuit 5 will be described.

[0070] The precharge circuit 5 provided in the motor drive device prevents a surge current that may be generated when precharging a DC link capacitor between the DC output side of a converter circuit and the DC input side of an inverter circuit provided in the motor drive device. The precharge circuit is provided on the DC output side or the AC input side of the converter circuit.

[0071] like Figure 8As shown, the precharge circuit 5 has switches 21-1 and 21-2 and a precharge resistor 22 connected in parallel with the switches 21-1 and 21-2. Examples of the switches 21-1 and 21-2 include relays and semiconductor switch elements. After the precharge is completed, the switch 21 is closed and a large current flows through it. Therefore, the switch 21 is composed of a plurality of switches 21-1 and 21-2 connected in parallel. By closing the plurality of switches 21-1 and 21-2 connected in parallel at the same time, a large current can be dispersedly flowed through each switch 21-1 and 21-2, and by opening the plurality of switches 21-1 and 21-2 connected in parallel at the same time, the large current can be cut off.

[0072] like Figure 7 As shown, switches 21-1 and 21-2 of the precharge circuit 5 and the precharge resistor 22 are mounted on a substrate 20. Various components 23 are also provided on the substrate 20. Examples of the various components 23 include heat-sensitive capacitors. Temperature sensors 11-1 and 11-2 are provided near the switches 21-1 and 21-2, respectively. As a modification, the temperature sensors 11-1 and 11-2 may also be provided near the heat-sensitive capacitors.

[0073] Next, a motor drive device including a fault detection device according to an embodiment of the present disclosure will be described.

[0074] Fig. 9 This is a diagram illustrating a motor drive device including a fault detection device according to an embodiment of the present disclosure.

[0075] As an example, an example of controlling the motor 300 by the motor drive device 100 connected to the AC power supply 200 is shown. In the present embodiment, the type of the motor 300 is not particularly limited, for example, it can be an induction motor or a synchronous motor. In addition, the number of phases of the AC power supply 200 and the motor 300 is not particularly limited to the present embodiment, for example, it can be three-phase or single-phase. In the illustrated example, the AC power supply 200 and the motor 300 are respectively set to three phases. An example of the AC power supply 200 is listed, there are three-phase AC 400V power supply, three-phase AC 200V power supply, three-phase AC 600V power supply, single-phase AC 100V power supply, etc. The machine provided with the motor 300 includes, for example, a machine tool, a robot, a forging machine, an injection molding machine, an industrial machine, etc.

[0076] The motor drive device 100 includes a fault detection device 1 , a converter circuit 2 , a DC link capacitor 3 , an inverter circuit 4 , and a precharge circuit 5 . An electromagnetic contactor 6 is provided between the motor drive device 100 and the AC power source 200 .

[0077] Regarding the fault detection device 1, as shown in FIG. Figures 1 to 8 As described.

[0078] The converter circuit 2 converts the AC power input from the AC power source 200 into DC power and outputs it to the DC link as the DC output side. The "DC link" is sometimes also referred to as a "DC link unit", "DC link", "DC link unit" or "DC intermediate circuit". The converter circuit 2 is composed of a three-phase bridge circuit when three-phase AC power is supplied from the AC power source 200, and is composed of a single-phase bridge circuit when single-phase AC power is supplied from the AC power source 200. In the example shown in the figure, the AC power source 200 is set as a three-phase AC power source, so the converter circuit 2 is composed of a three-phase bridge circuit. As examples of the converter circuit 2, there are diode rectifiers, 120-degree power-on rectifiers, and PWM switch control rectifiers. For example, when the converter circuit 2 is a 120-degree power-on rectifier and a PWM switch control rectifier, it is composed of a bridge circuit of semiconductor switching elements and diodes connected in anti-parallel thereto, and each switching element is turned on and off according to a drive instruction received from a host control device (not shown) to perform power conversion in both AC and DC directions. In this case, examples of the switching element include FET, IGBT, thyristor, GTO, transistor, etc., but other semiconductor switching elements may also be used.

[0079] An electromagnetic contactor 6 is provided on the AC input side of the converter circuit 2. The electromagnetic contactor 6 opens and closes the current path of the AC input current from the AC power source 200 to the converter circuit 2. The closing action of forming the current path of the AC input current from the AC power source 200 to the converter circuit 2 is achieved by closing the contacts of the electromagnetic contactor 6, and the opening action of cutting off the current path of the AC input current from the AC power source 200 to the converter circuit 2 is achieved by separating the contacts of the electromagnetic contactor 6. In addition, on the AC input side of the converter circuit 2, in addition to the electromagnetic contactor 6, an AC reactor, an AC line filter, etc. are sometimes provided, but they are omitted in the figure.

[0080] A DC link capacitor 3 is provided in a DC link connecting the DC output side of the converter circuit 2 and the DC input side of the inverter circuit 4. The DC link capacitor 3 has a function of storing DC power used for the inverter circuit 4 to generate AC power and a function of suppressing the pulsation amount of the DC output of the converter circuit 2. Examples of the DC link capacitor 3 include an electrolytic capacitor, a film capacitor, and the like.

[0081] The inverter circuit 4 is connected to the converter circuit 2 via a DC link, and converts the DC power in the DC link into AC power for driving the motor and outputs it. As an example of the inverter circuit 4, there is a PWM control inverter composed of a bridge circuit of a rectifier element and a semiconductor switch element connected in anti-parallel thereto, etc. As examples of semiconductor switch elements, there are FETs, IGBTs, thyristors, GTOs, transistors, etc., but other semiconductor elements may also be used. The inverter circuit 4 is composed of a three-phase bridge circuit when the motor 300 is a three-phase AC motor, and is composed of a single-phase bridge circuit when the motor 300 is a single-phase AC motor. In the example shown in the figure, the motor 300 is set as a three-phase AC motor, so the inverter circuit 4 is composed of a three-phase bridge circuit. The inverter circuit 4 performs PWM control on the on-off action of the internal semiconductor switch element according to the instruction of the upper control device (not shown), thereby converting the DC power in the DC link into AC power for driving the motor and outputting it. The motor 300 controls the speed, torque or rotor position according to the AC power supplied from the inverter circuit 4. Furthermore, the inverter circuit 4 appropriately performs PWM control on the on-off operation of the switching element, thereby converting the AC power regenerated by the motor 300 into DC power and returning the DC power to the DC link on the DC side.

[0082] In order to prevent a possible inrush current generated when precharging (initial charging) the DC link capacitor 3 before starting to drive the motor 300 by the motor drive device 100, a precharging circuit (initial charging circuit) 5 is provided. The precharging circuit 5 is provided on the DC output side or the AC input side of the converter circuit 2, but Fig. 9 In the example shown, the precharge circuit 5 is provided on the DC output side of the converter circuit 2 as an example.

[0083] The precharge circuit 5 has switches 21-1 and 21-2 and a precharge resistor 22 connected in parallel with these switches 21-1 and 21-2. Examples of switches 21-1 and 21-2 include relays and semiconductor switch elements. In the illustrated example, as an example, two switches 21-1 and 21-2 are connected in parallel, but more than three switches may be connected in parallel. By closing a plurality of switches 21-1 and 21-2 connected in parallel at the same time, a large current can be dispersedly passed through each switch 21-1 and 21-2, and by opening a plurality of switches 21-1 and 21-2 connected in parallel at the same time, a large current can be cut off.

[0084] During the pre-charging period from immediately after the motor drive device 100 is started (immediately after the power supply is turned on) to before the start of the drive of the motor 300, the switches 21-1 and 21-2 are simultaneously opened (disconnected) according to the opening instruction received from the upper control device (not shown). During the pre-charging period, the switches 21-1 and 21-2 are maintained in the open state, so the current output from the converter circuit 2 flows into the DC link capacitor 3 as a charging current via the pre-charging resistor 22, and the DC link capacitor 3 is charged (pre-charged). In this way, during the pre-charging period, the current output from the converter circuit 2 flows in the pre-charging resistor 22, so that the generation of the rush current can be prevented. When the DC link capacitor reaches a predetermined charging voltage and the pre-charging is completed, the switches 21-1 and 21-2 are simultaneously closed (turned on) according to the closing instruction received from the upper control device (not shown). After the pre-charging is completed, the drive of the motor 300 is started, and the current output from the converter circuit 2 flows to the inverter circuit 4 and the DC link capacitor 3 through the closed switches 21-1 and 21-2.

[0085] Temperature sensors 11-1 and 11-2 are provided near the switches 21-1 and 21-2 on the substrate on which the switches 21-1 and 21-2 are mounted. The failure detection device 1 determines whether any of the switches 21-1 and 21-2 in the precharge circuit 5 has an open failure.

[0086] During the pre-charge period, switches 21-1 and 21-2 are open (disconnected), so current does not flow through switches 21-1 and 21-2. Therefore, the temperature of the substrate near switches 21-1 to 21-n and the substrate on which these switches 21-1 to 21-n are mounted changes little, and the combined resistance value detected by the detection unit 12 in the fault detection device 1 hardly changes. The detection unit 12 detects the combined resistance value of the temperature sensors 11-1 and 11-2, and the determination unit 13 performs a fault determination process based on the combined resistance value detected by the detection unit 12. As shown in FIG. Figure 3 as well as Figure 4 As described above, when the temperature sensors 11 - 1 and 11 - 2 are formed of PTC thermistors, the first threshold value R th1 The value is set to be larger than the combined resistance value when all switches 21-1 and 21-2 are normal, so that the determination unit 13 does not determine that the combined resistance value detected by the detection unit 12 exceeds the first threshold value R th1 Therefore, it is not determined to be an open circuit fault. Figure 5 as well as Figure 6 As described above, when the temperature sensors 11-1 and 11-2 are composed of NTC thermistors, the second threshold value R th2The value is set to be smaller than the combined resistance value when all switches 21-1 and 21-2 are normal, so that the determination unit 13 does not determine that the combined resistance value detected by the detection unit 12 is lower than the second threshold value R th2 Therefore, it is not determined that an open circuit fault has occurred.

[0087] After the pre-charging is completed, the host control device (not shown) outputs a closing command to the switches 21 - 1 and 21 - 2 .

[0088] When the switches 21-1 and 21-2 are normally closed according to the closing command, the current output from the converter circuit 2 flows dispersedly through the closed switches 21-1 and 21-2. Therefore, the temperature of the substrate near the switches 21-1 to 21-n and on which the switches 21-1 to 21-n are mounted changes little, and the combined resistance value detected by the detection unit 12 in the fault detection device 1 hardly changes. Figure 3 as well as Figure 4 As described above, when the temperature sensors 11-1 and 11-2 are formed of PTC thermistors, the determination unit 13 does not determine that the combined resistance value detected by the detection unit 12 exceeds the first threshold value R th1 Therefore, it is not determined to be an open circuit fault. Figure 5 as well as Figure 6 As described above, when the temperature sensors 11-1 and 11-2 are composed of NTC thermistors, the determination unit 13 does not determine that the combined resistance value detected by the detection unit 12 is lower than the second threshold value R th2 Therefore, it is not determined that an open circuit fault has occurred.

[0089] On the other hand, when an open circuit fault occurs in which at least one of the switches 21-1 and 21-2 does not close but remains open despite the closing instruction for all switches 21-1 and 21-2, current flows intensively through the switch that is normally closed according to the closing instruction, causing abnormal overheating. As a result, the resistance value of the temperature sensor installed near the abnormally overheated switch changes significantly. Figure 3 as well as Figure 4 As described above, when the temperature sensors 11-1 and 11-2 are formed of PTC thermistors, the determination unit 13 determines that the combined resistance value detected by the detection unit 12 exceeds the first threshold value R th1 Therefore, it is determined that an open circuit fault has occurred. Figure 5 and Figure 6 As described above, when the temperature sensors 11-1 and 11-2 are composed of NTC thermistors, the determination unit 13 determines that the combined resistance value detected by the detection unit 12 is lower than the second threshold value R th2 , therefore, it is determined that an open circuit fault occurs.

[0090] In this way, the fault detection device 1 can detect the occurrence of at least one open circuit fault in the precharge circuit 5 including the plurality of switches 21 - 1 and 21 - 2 driven in parallel.

[0091] The fault determination result of the determination unit 13 in the fault detection device 1 can be displayed on a display unit, for example, or can be output by an audio device that emits sound, such as voice, speaker, buzzer, bell, etc. In addition, based on the fault determination result of the determination unit 13 in the fault detection device 1, the motor drive device 100 can be stopped urgently, or the machine provided with the motor drive device 100 can be made to perform abnormal avoidance action.

[0092] Furthermore, the fault detection device 1 is not limited to the above-described precharge circuit 5 , and can detect the occurrence of an open-circuit fault in a circuit having a plurality of switches driven in parallel.

[0093] For example, Fig. 9 As shown, when the AC power supply 200 is three-phase, the electromagnetic contactor 6 also has three-phase contact circuits correspondingly, and these contact circuits are driven in parallel. Temperature sensors are set near each of the three phases of the contact circuit, and these temperature sensors are electrically connected in series to form the above-mentioned detection unit 12 and determination unit 13, thereby forming a fault detection device 1, which can detect the occurrence of an open circuit fault between contacts in the electromagnetic contactor 6.

[0094] In addition, for example, sometimes Fig. 9 The motor drive device 100 shown is provided with a dynamic braking circuit (not shown) for stopping the motor 300. The dynamic braking circuit is composed of a relay provided between the input terminals of the motor 300 and a dynamic braking resistor connected in series therewith. When dynamic braking is applied, the relay is closed to short-circuit the input terminals of the motor 300 (phases between the motor windings) on the basis of cutting off the supply of driving power to the motor 300. Even if the motor 300 is electrically disconnected from the power supply, there is still excitation flux. The motor 300 rotating due to inertia works as a generator. Therefore, the current generated thereby flows into the dynamic braking resistor via the closed relay, generating a deceleration torque in the motor 300. Temperature sensors are provided near each of the relays in the dynamic braking circuit, and these temperature sensors are electrically connected in series with each other to form the above-mentioned detection unit 12 and determination unit 13, thereby forming a fault detection device 1, which can detect the occurrence of an open circuit fault of a switch in the dynamic braking circuit.

[0095] In addition, for example, Fig. 9The inverter circuit 4 in the motor drive device 100 shown in the figure is provided with a plurality of semiconductor switching elements. In addition, when the converter circuit 2 is a 120-degree conduction mode rectifier and a PWM switch control mode rectifier, a plurality of semiconductor switching elements are also provided in the converter circuit 2. Temperature sensors are provided near each of these semiconductor switching elements, and these temperature sensors are electrically connected in series to form the above-mentioned detection unit 12 and determination unit 13, thereby forming a fault detection device 1 that can detect the occurrence of an open circuit fault of a semiconductor switching element in the inverter circuit 4 and the converter circuit 2.

[0096] Explanation of symbols

[0097] 1 Fault detection device,

[0098] 2 Converter circuit,

[0099] 3 DC link capacitors,

[0100] 4 Inverter circuit,

[0101] 5 Pre-charge circuit,

[0102] 6 Electromagnetic contactor,

[0103] 11. 11-1~11-m temperature sensor,

[0104] 12. Inspection Department,

[0105] 13. Judgment Department,

[0106] 20 substrate,

[0107] 21, 21-1 to 21-n switch,

[0108] 22 Pre-charge resistor,

[0109] 23 various parts,

[0110] 100 Motor drive device,

[0111] 200 AC power supply,

[0112] 300 electric motor.

Claims

1. A fault detection device for detecting a fault of a switch that selectively switches between conducting and non-conducting on a current path, characterized in that: The fault detection device comprises: at least two temperature sensors, the resistance value between the terminals of which changes according to the temperature, are provided near the at least two switches connected in parallel to each other and are electrically connected in series to each other; a detection unit configured to detect a combined resistance value of the at least two temperature sensors; as well as A determination unit determines that at least one of the switches has a failure based on the combined resistance value.

2. The fault detection device according to claim 1, characterized in that: Each of the at least two temperature sensors is a PTC thermistor whose resistance value increases as the temperature rises, The determination unit determines that at least one of the switches has failed when the combined resistance value exceeds a predetermined first threshold value.

3. The fault detection device according to claim 1, characterized in that: Each of the at least two temperature sensors is an NTC thermistor whose resistance value decreases as the temperature increases, The determination unit determines that at least one of the switches has failed when the combined resistance value is lower than a predetermined second threshold value.

4. The fault detection device according to any one of claims 1 to 3, characterized in that: The switch is a relay.

5. The fault detection device according to any one of claims 1 to 3, characterized in that: The switch is a semiconductor switching element.

6. The fault detection device according to any one of claims 1 to 3, characterized in that: The switch is an electromagnetic contactor.

7. A motor drive device, characterized in that: have: The fault detection device according to any one of claims 1 to 6; A converter circuit that converts AC power input from an AC power source into DC power and outputs the DC power; A DC link capacitor provided in a DC link serving as a DC output side of the converter circuit; an inverter circuit that converts the DC power in the DC link into AC power for driving the motor and outputs the AC power; as well as A precharge circuit includes the switch and a precharge resistor connected in parallel with the switch, and is used to prevent a surge current when precharging the DC link capacitor.

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