JP6279192B1 - Inverter device and abnormality detection method for inverter device - Google Patents

Abstract

The inverter device (100) includes a converter unit (11) that converts an AC voltage into a DC voltage, a smoothing capacitor (12) that smoothes the DC voltage output from the converter unit, and a DC voltage that is smoothed by the smoothing capacitor. Inverter unit (13) for converting to AC voltage, limiting resistor (14) having a positive temperature characteristic or a characteristic that the resistance value increases due to deterioration, and contact element (15) whose open or short circuit is controlled by a contact signal Are a parallel circuit connected in parallel, a charging circuit (20) connected between the converter unit and the smoothing capacitor, and a voltage detection unit for detecting the voltage across the smoothing capacitor and outputting it as a voltage detection signal (16) and a predetermined period including the time when the contact signal is switched so that the contact element is short-circuited from being opened based on the voltage detection signal. Is greater than the voltage difference is the reference value of the voltage across, including limit detection unit determines that the resistance value is abnormal resistor (17), the.

Description

  The present invention relates to an inverter device including a charging circuit using a limiting resistor and an abnormality detection method for the inverter device.

  A general inverter device includes a smoothing capacitor in a direct current intermediate portion. Such an inverter device charges a smoothing capacitor by rectifying an AC voltage applied from an AC power source by a converter unit at startup. However, during the initial charging immediately after the power is turned on, a large inrush current flows because the smoothing capacitor is not charged. In order to suppress the inrush current during the initial charging, a charging circuit including a resistor serving as a limiting resistor and a contact element such as a relay that short-circuits both ends of the resistor is provided in the inverter device.

  A technique for detecting an abnormality of the charging circuit is disclosed in Patent Document 1 below. In Patent Document 1, the voltage across the smoothing capacitor is detected using an existing voltage detector that is generally provided for the purpose of protecting the smoothing capacitor, and the slope of the voltage detection value based on the detected voltage detection signal is disclosed. From this, it is described that a short-circuit failure or an open-circuit failure of a contact element is detected and a failure is indicated.

JP 2012-120376 A

  In Patent Document 1, when the slope of the voltage rise of the voltage across the smoothing capacitor in a predetermined period after the contact signal becomes a value indicating the ON state is greater than or equal to a reference value, the contact element is not open failure and is normal It is judged that. However, the technique described in Patent Document 1 has a problem in that an abnormality of the charging circuit due to deterioration of the limiting resistance or the like cannot be detected.

  The present invention has been made in view of the above, and an object of the present invention is to obtain an inverter device that can detect an abnormality of a charging circuit with a simple configuration by using a change in the resistance value of a limiting resistor.

  In order to solve the above-described problems and achieve the object, the present invention provides a converter unit that converts an AC voltage into a DC voltage, a smoothing capacitor that smoothes a DC voltage output from the converter unit, and a smoothing capacitor An inverter unit that converts the DC voltage into an AC voltage, a limiting resistor that has a positive temperature characteristic or a characteristic that the resistance value increases due to deterioration, and a contact element that is controlled to open or short by a contact signal are connected in parallel It is a connected parallel circuit, and includes a charging circuit connected between the converter unit and the smoothing capacitor, and a voltage detection unit that detects a voltage across the smoothing capacitor and outputs it as a voltage detection signal. The present invention provides a limiting resistor in the case where the voltage difference between the both-end voltages in a predetermined period including a time at which the contact signal is switched so that the contact element is short-circuited from being opened based on the voltage detection signal is larger than a reference value. It is further characterized by further comprising a detection unit that determines that the resistance value of is abnormal.

  The inverter device according to the present invention has an effect that the abnormality of the charging circuit can be detected with a simple configuration by using the change in the resistance value of the limiting resistor.

1 is a schematic configuration diagram of an inverter device according to a first embodiment of the present invention. A flowchart of an initial charging operation of the inverter device according to the first embodiment. Time chart of initial charging operation of inverter device when charging circuit according to first embodiment is normal Time chart of the initial charging operation of the inverter device when the thermistor according to the first embodiment becomes abnormal The flowchart when the contact element of the inverter apparatus concerning Embodiment 2 of this invention has an open failure. Time chart when the contact element of the inverter device according to the second embodiment has an open failure 1 is a block diagram showing a configuration of a microcomputer according to first and second embodiments;

  Hereinafter, an inverter device and an abnormality detection method for the inverter device according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a schematic configuration diagram of an inverter device 100 according to the first embodiment of the present invention. In FIG. 1, a commercial AC power source 1 is connected to an inverter device 100 via a circuit breaker 2, and the inverter device 100 drives an electric motor 3. In the state where the circuit breaker 2 is open, the AC voltage from the AC power source 1 is not supplied to the inverter device 100, but when the circuit breaker 2 is closed by the input of a signal from a signal line (not shown), the AC power source The AC voltage from 1 is supplied to the inverter device 100.

  The inverter device 100 smoothes the DC voltage output from the converter unit 11 that is connected between the DC bus 21 and the converter unit 11 that performs full-wave rectification on the AC voltage supplied from the AC power source 1 and converts it into a DC voltage. A smoothing capacitor 12; and an inverter unit 13 that is connected between the DC buses 21 and converts the DC voltage smoothed by the smoothing capacitor 12 into an AC voltage having a target frequency and voltage. That is, the inverter unit 13 converts the smoothed DC voltage at both ends of the smoothing capacitor 12 into an AC voltage. The DC bus 21 is a power supply line that supplies a DC voltage to the inverter unit 13. Here, the inverter unit 13 includes a semiconductor switching element such as an IGBT (Insulated Gate Bipolar Transistor) and a reflux diode. A specific example of the smoothing capacitor 12 is an electrolytic capacitor.

  Furthermore, the inverter device 100 includes a charging circuit 20 that is connected between the converter unit 11 and the smoothing capacitor 12 and initially charges the smoothing capacitor 12. The charging circuit 20 is a parallel circuit in which a thermistor 14 that is a limiting resistor and a contact element 15 are connected in parallel. The thermistor 14 has a positive temperature characteristic. The positive temperature characteristic is a characteristic that the resistance value increases as the temperature rises. The thermistor 14 is a current limiting element that is connected between the converter unit 11 and the smoothing capacitor 12 and limits the initial charging current to the smoothing capacitor 12. The contact element 15 is an element realized by a relay or the like that can be in an open or shorted state. The contact element 15 is connected in parallel to the thermistor 14 and can short-circuit both ends of the thermistor 14. The thermistor 14 is not limited as long as it is a limiting resistor that has an impedance component and can limit the inrush current and has a positive temperature characteristic. Further, if the thermistor 14 has a positive temperature characteristic as a whole, one limiting resistor, a plurality of limiting resistors connected in parallel, a plurality of limiting resistors connected in series, or a combination of parallel connection and series connection are combined. Any one of a plurality of limiting resistors may be used.

  Further, the inverter device 100 includes a voltage detection unit 16 that detects a DC voltage across the smoothing capacitor 12, a charging circuit abnormality detection unit 17 that is a detection unit that outputs an abnormality detection signal, and a PWM (Pulse Width). The inverter control part 18 which outputs a Modulation signal, and the display part 19 which performs abnormality display are provided.

  The voltage detector 16 detects a DC voltage that is the voltage across the smoothing capacitor 12 and outputs the detected voltage across the smoothing capacitor 12 to the charging circuit abnormality detector 17 and the inverter controller 18 as a voltage detection signal. The voltage detection unit 16 is generally provided in the inverter device 100 for the purpose of protecting the smoothing capacitor 12 withstand voltage.

  The charging circuit abnormality detection unit 17 can detect an abnormality of the charging circuit 20 and can control the opening or shorting of the contact element 15 by transmitting a relay signal, which is a contact signal, to the contact element 15. The contact signal takes either a value indicating an off state or a value indicating an on state. In the following, it is assumed that the contact signal is on when the contact signal is a value indicating the on state, and the contact signal is off when the contact signal is a value indicating the off state. When the contact signal is on, the contact element 15 is controlled to short-circuit, and when the contact signal is off, the contact element 15 is controlled to open. When the power to the inverter device 100 is turned on, the charging circuit abnormality detection unit 17 determines the voltage across the smoothing capacitor 12 immediately before switching the contact signal from the off state to the on state based on the voltage detection signal from the voltage detection unit 16. A voltage difference from the voltage across the smoothing capacitor 12 immediately after the contact signal is turned on is calculated. The charging circuit abnormality detection unit 17 can detect that the resistance value of the thermistor 14 has changed from the calculated voltage difference to an abnormal value. Thereby, the charging circuit abnormality detection unit 17 determines the temperature abnormality of the thermistor 14. Furthermore, the charging circuit abnormality detection unit 17 can detect an open failure of the contact element 15 based on the fluctuation of the voltage detection signal given from the voltage detection unit 16. The charging circuit abnormality detection unit 17 outputs an abnormality detection signal to the inverter control unit 18 and the display unit 19 when it is determined that the resistance value of the thermistor 14 is abnormal and when an open failure of the contact element 15 is detected.

  The inverter control unit 18 calculates a voltage command signal based on a frequency command value from a frequency setter (not shown), and executes a calculation for comparing the voltage command signal with the carrier frequency signal, which is a control signal PWM. A signal is generated and output to the inverter unit 13. The PWM signal is a signal for controlling the on state or the off state of each semiconductor switching element constituting the inverter unit 13.

  The display unit 19 displays an abnormality based on an abnormality detection signal output when the charging circuit abnormality detection unit 17 detects an abnormality.

  FIG. 2 is a flowchart of the initial charging operation of the inverter device 100 according to the first embodiment. FIG. 2 illustrates an initial charging operation in which the contact signal changes to the ON state before the charging of the smoothing capacitor 12 is completed. FIG. 3 is a time chart of the initial charging operation of the inverter device 100 when the charging circuit 20 according to the first embodiment is normal. The case where the charging circuit 20 is normal is a case where both the thermistor 14 and the contact element 15 are normal. Hereinafter, an initial charging operation when the charging circuit 20 is normal will be described with reference to FIGS. 2 and 3.

(Initial charging operation when the charging circuit 20 is normal)
When starting the inverter device 100, first, when a signal is input from a signal line (not shown) at time t0 and the circuit breaker 2 is closed, the AC voltage from the AC power source 1 is supplied to the converter unit 11. (Step S11). The supplied AC voltage is rectified by the converter unit 11, and initial charging of the smoothing capacitor 12 is started. At this time, since the contact element 15 is open, the charging current suppressed through the thermistor 14 flows through the smoothing capacitor 12. The voltage detection signal indicating the voltage across the smoothing capacitor 12 rises according to a time constant determined by the resistance of the thermistor 14 and the capacitance of the smoothing capacitor 12.

  At time t1, the voltage detection signal reaches a predetermined voltage V1 (step S12). The voltage V1 is determined based on the value of the AC voltage of the AC power source 1 and the like. Thereafter, the voltage detection unit 16 detects the voltage V2 that is the voltage across the smoothing capacitor 12 at time t2 immediately before the charging circuit abnormality detection unit 17 switches the contact signal to the contact element 15 from the off state to the on state (step S2). S13), and output as a voltage detection signal. The charging circuit abnormality detection unit 17 to which the voltage detection signal indicating the voltage V2 is input stores the voltage V2. Time t2 is the time immediately before time t3, and time t3 is the time when the contact signal is switched from the off state to the on state. Time t3 is a time after a predetermined time T1 from time t1. Further, the time from time t2 to time t3 is determined in advance. And the charging circuit abnormality detection part 17 switches a contact signal from an OFF state to an ON state at the time t3 (step S14). When the contact signal is turned on, the contact element 15 is short-circuited to increase the charging current, and the voltage across the smoothing capacitor 12 increases to the voltage V3.

  Thereafter, the voltage detection unit 16 detects the voltage V3 that is the voltage across the smoothing capacitor 12 at time t4 immediately after the charging circuit abnormality detection unit 17 switches the contact signal to the contact element 15 from the off state to the on state ( Step S15), and output as a voltage detection signal. The charging circuit abnormality detection unit 17 to which the voltage detection signal indicating the voltage V3 is input stores the voltage V3. Time t4 is a time immediately after time t3, and the time from time t3 to time t4 is determined in advance. Therefore, a predetermined period is from time t2 to time t4.

  The charging circuit abnormality detection unit 17 calculates V3-V2 that is a voltage difference between both ends of the smoothing capacitor 12 between time t2 and time t4, and whether or not the voltage difference is equal to or less than a preset reference value. Is determined (step S16). When it is determined that the voltage difference is equal to or less than the reference value (step S16: Yes), the charging circuit abnormality detection unit 17 determines that the thermistor 14 is normal and does not output an abnormality detection signal. Therefore, since the inverter control unit 18 has not received the abnormality detection signal, when the operation signal is input, the inverter control unit 18 outputs a PWM signal (step S17).

  FIG. 4 is a time chart of the initial charging operation of the inverter device 100 when the thermistor 14 according to the first embodiment becomes abnormal. Specifically, when the thermistor 14 becomes abnormal, the temperature of the thermistor 14 having a positive temperature characteristic rises due to the current heating caused by turning on the AC power supply 1 in step S11 or the influence of the surrounding environment. This is a case where the value increases from an assumed value and becomes an abnormal value. Hereinafter, an initial charging operation when the thermistor 14 becomes abnormal will be described with reference to FIGS. 2 and 4.

(Initial charging operation when thermistor 14 becomes abnormal)
When the initial charging of the smoothing capacitor 12 is started in step S11, if the resistance value of the thermistor 14 is higher than the value assumed for the above cause, it is determined by the resistance of the thermistor 14 and the capacitance of the smoothing capacitor 12. The time constant is larger than when the thermistor 14 is normal. As a result, as shown in FIG. 4, the voltage rise of the smoothing capacitor 12 is moderate as compared with the case of FIG. 3 in which the thermistor 14 is normal.

  At time t11, the voltage across the smoothing capacitor 12 reaches the predetermined voltage V1 (step S12). Thereafter, the voltage detection unit 16 detects the voltage V21 that is the voltage across the smoothing capacitor 12 at time t21 immediately before the charging circuit abnormality detection unit 17 switches the contact signal to the contact element 15 from the OFF state to the ON state (step S21). S13), and output as a voltage detection signal. The charging circuit abnormality detection unit 17 to which the voltage detection signal indicating the voltage V21 is input stores the voltage V21. Time t21 is the time immediately before time t31, and time t31 is the time when the contact signal is switched from the off state to the on state. Time t31 is a time after a predetermined time T1 from time t11. Furthermore, the time from time t21 to time t31 is the same as the time from time t2 to time t3 in FIG. And the charging circuit abnormality detection part 17 switches a contact signal from an OFF state to an ON state at the time t31 (step S14). When the contact signal is turned on, the contact element 15 is short-circuited to increase the charging current, and the voltage across the smoothing capacitor 12 increases to the voltage V3.

  Thereafter, the voltage detection unit 16 detects the voltage V3 that is the voltage across the smoothing capacitor 12 at time t41 immediately after the charging circuit abnormality detection unit 17 switches the contact signal to the contact element 15 from the off state to the on state ( Step S15), and output as a voltage detection signal. The charging circuit abnormality detection unit 17 to which the voltage detection signal indicating the voltage V3 is input stores the voltage V3. Time t41 is a time immediately after time t31, and the time from time t31 to time t41 is the same as the time from time t3 to time t4 in FIG. Therefore, the period from time t21 to time t41 is also the same as the period from time t2 to time t4 in FIG.

  As described above, the rise in the voltage across the smoothing capacitor 12 from time t11 in FIG. 4 is more gradual than the rise in the voltage across the smoothing capacitor 12 from time t1 in FIG. The voltage is smaller than the voltage V2 in FIG. 3 when the thermistor 14 is normal. The voltage V3 is the voltage across the smoothing capacitor 12 when the contact element 15 is short-circuited, and therefore does not change from when the thermistor 14 is normal. Therefore, the voltage difference V3-V21 between both ends of the smoothing capacitor 12 during the period from time t21 to time t41 becomes the voltage difference V3-V2 between both ends of the smoothing capacitor 12 during the period from time t2 to time t4 in FIG. Compared to a larger value. Therefore, the charging circuit abnormality detection unit 17 calculates the voltage difference V3-V21, determines whether the voltage difference is equal to or less than the reference value (step S16), and determines that the voltage difference is larger than the reference value ( In step S16: No), it is determined that the resistance value of the thermistor 14 is abnormal, and an abnormality detection signal is output (step S18). As a result, the inverter control unit 18 that has received the abnormality detection signal does not output the PWM signal to the inverter unit 13 even if the operation signal is input. The display unit 19 that has received the abnormality detection signal can display that an abnormality has occurred in the resistance value of the thermistor 14.

  As described above, when the thermistor 14 having the positive temperature characteristic is used as the limiting resistor of the charging circuit 20, the resistance value of the thermistor 14 is large due to abnormality in the surrounding environment such as current heating or high ambient temperature. Value. As a result, the voltage difference V3-V21 becomes larger than a preset reference value, so that it is possible to determine whether the temperature of the thermistor 14 or the ambient temperature is abnormal.

  When the input power supply voltage changes depending on the environment of the AC power supply 1, even if a change in the value of the voltage V3 or a rising behavior of the voltage across the smoothing capacitor 12 after the power is turned on, the thermistor 14 If there is an abnormality in the resistance value, the voltage difference between both ends of the smoothing capacitor 12 before and after switching the contact signal from the OFF state to the ON state becomes larger than the reference value. Therefore, by determining an abnormality in the resistance value of the thermistor 14 from this voltage difference, an abnormality in the thermistor 14 can be detected regardless of the input power supply voltage.

  Further, in the above, by using the thermistor 14 having a positive temperature characteristic as the limiting resistance of the charging circuit 20, an increase in the resistance value due to the temperature rise of the thermistor 14 caused by turning on the AC power supply 1 or the increase in the ambient temperature is diagnosed. However, according to the inverter device 100 according to the first embodiment, it is possible to diagnose an abnormality in the resistance value itself of the limiting resistor of the charging circuit 20.

  When a normal resistor is used as the limiting resistor, the resistance value may increase due to deterioration of the resistor. That is, a resistor having a characteristic that the resistance value increases due to deterioration may be used as the limiting resistor of the charging circuit 20. Also in this case, as a result of the resistance value of the limiting resistor becoming large, the voltage difference between both ends of the smoothing capacitor 12 before and after switching the contact signal from the OFF state to the ON state becomes larger than the reference value, and the resistance value of the limiting resistor is abnormal. Can be diagnosed.

  Further, a circuit that switches the contact signal to the on state after determining that the voltage across the smoothing capacitor 12 is saturated by measuring the voltage detection signal output from the voltage detection unit 16 at an appropriate time interval is provided in the inverter device 100. May be granted. Even in such an inverter device 100, the input current to the power supply circuit that supplies power to the control circuit and the display unit 19 and the like that are normally provided, and the temperature rise of the thermistor 14 having a positive temperature characteristic, becomes an excessive value. Since the voltage difference determined from the resistance value appears as a voltage difference before and after switching the contact signal to the contact element 15 from the off state to the on state, an abnormality in the resistance value can be similarly detected.

  As described above, according to the inverter device 100 according to the first embodiment, the change in the resistance value of the limiting resistor is achieved by using the voltage detection unit 16 that is normally provided for the purpose of protecting the smoothing capacitor 12 withstand voltage. The abnormality of the charging circuit 20 can be detected with a simple configuration. Therefore, an increase in cost and an increase in size of the apparatus can be suppressed.

Embodiment 2. FIG.
The configuration of the inverter device 100 according to the second embodiment is the same as that shown in FIG. FIG. 5 is a flowchart when the contact element 15 of the inverter device 100 according to the second embodiment of the present invention has an open failure. FIG. 6 is a time chart when the contact element 15 of the inverter device 100 according to the second embodiment has an open failure. Hereinafter, the operation of the inverter device 100 when the contact element 15 has an open failure will be described with reference to FIGS. 5 and 6.

(Operation of the inverter device 100 when the contact element 15 has an open failure)
When starting up the inverter device 100, first, when the circuit breaker 2 is closed at time t0, an AC voltage is supplied to the converter unit 11 (step S21). The supplied AC voltage is rectified by the converter unit 11, and initial charging of the smoothing capacitor 12 is started. At this time, since the contact element 15 is open, the charging current suppressed through the thermistor 14 flows through the smoothing capacitor 12. The voltage detection signal indicating the voltage across the smoothing capacitor 12 rises according to a time constant determined by the resistance of the thermistor 14 and the capacitance of the smoothing capacitor 12.

  At time t12, the voltage detection signal reaches a predetermined voltage V1 (step S22). Furthermore, at time t32 after a predetermined time T1 from time t12, the charging circuit abnormality detection unit 17 switches the contact signal from the off state to the on state (step S23). Here, if the contact element 15 has an open failure due to some cause, the contact element 15 remains open even when an ON contact signal is received. Thereafter, when the operation signal is input and the inverter control unit 18 outputs the PWM signal, the current flowing through the electric motor 3 continues to flow through the thermistor 14, so that the temperature of the thermistor 14 having the positive temperature characteristic rises.

  When the temperature of the thermistor 14 rises and the resistance value increases, no current flows from the output of the converter unit 11 to the smoothing capacitor 12, and the voltage across the smoothing capacitor 12 indicated by the voltage detection signal gradually decreases (step S24). When the voltage at both ends of the smoothing capacitor 12 indicated by the voltage detection signal decreases and becomes equal to or lower than the voltage V32 which is the predetermined first threshold value shown in FIG. 6, the inverter control unit 18 cuts off the PWM signal (step S25). An alarm is output to the display unit 19. The display unit 19 can display an alarm that the PWM signal is cut off. When the PWM signal is cut off, no current flows through the electric motor 3, and as a result, the current flowing through the thermistor 14 for driving the electric motor 3 is cut off, and the amount of current decreases.

  When the amount of current flowing through the thermistor 14 decreases, the temperature of the thermistor 14 starts to decrease due to the heat of the thermistor 14 being dissipated to the outside air, and the resistance value of the thermistor 14 begins to decrease to a desirable value. Thus, the voltage across the smoothing capacitor 12 indicated by the voltage detection signal gradually increases (step S26). When the voltage across the smoothing capacitor 12 indicated by the voltage detection signal rises and becomes equal to or higher than the voltage V33 which is a predetermined second threshold value as a voltage value higher than the first threshold value shown in FIG. A signal is output (step S27), the alarm output is stopped, and the alarm is not displayed on the display unit 19. As described below, the interruption of the PWM signal in step S25 and the output of the PWM signal in step S27 are repeated until the charging circuit abnormality detection unit 17 determines that an open failure has occurred in the contact element 15. Become.

  Based on the voltage detection signal, the charging circuit abnormality detection unit 17 determines whether or not the repetitive operation of blocking the PWM signal and outputting the PWM signal is equal to or more than a predetermined number of times within a predetermined time period ( Step S28). Specifically, based on the voltage detection signal given from the voltage detection unit 16, the number of times that the voltage across the smoothing capacitor 12 becomes equal to or higher than the voltage V33 after the voltage across the smoothing capacitor 12 becomes equal to or lower than the voltage V32 becomes equal to or higher than the specified number of times within the specified time. Based on this, the charging circuit abnormality detection unit 17 executes the determination in step S28. When the charging circuit abnormality detection unit 17 determines that the specified time has not elapsed since the start of the output of the PWM signal, or the number of times the PWM signal is cut off and the PWM signal is output repeatedly is less than the specified number of times within the specified time. When it determines with there (step S28: No), it returns to step S24. When it is determined that the number of times the PWM signal is interrupted and the PWM signal is repeatedly output is greater than or equal to the specified number of times within the specified time (step S28: Yes), the charging circuit abnormality detection unit 17 causes an open failure in the contact element 15. It is determined that the abnormality is occurring, and an abnormality detection signal is output (step S29). As a result, the inverter control unit 18 that has received the abnormality detection signal does not output the PWM signal to the inverter unit 13 even if the operation signal is input. Further, the display unit 19 that has received the abnormality detection signal can display that an open failure has occurred in the contact element 15. As described above, according to the inverter device 100 according to the second embodiment, it is possible to detect an open failure of the contact element 15 after the smoothing capacitor 12 is completely charged by using a change in the resistance value of the limiting resistor. Therefore, the abnormality of the charging circuit 20 can be detected with a simple configuration.

  As a method for determining that an open failure has occurred in the contact element, in Patent Document 1, if an open failure has occurred in the contact element based on the behavior of the voltage across the electrolytic capacitor during initial charging immediately after power-on. How to judge is shown. However, since the contact element failure is determined at the initial charge immediately after the power is turned on, if the contact element open failure occurs after the charging is completed, the open failure cannot be detected and the output of the PWM signal is continued. There was a problem. On the other hand, since the inverter device 100 according to the second embodiment can detect after the completion of charging, even when the opening failure of the contact element 15 occurs after the charging is completed, the opening failure of the contact element 15 is detected. The PWM signal can be cut off.

  Further, as another method for determining that an open circuit failure has occurred in the contact element, there is a method for determining by mounting a temperature detecting element around a thermistor that is a limiting resistor. Specifically, when an open circuit failure has occurred in the contact element, heat generation of the thermistor due to the current flowing through the motor continuing to flow through the thermistor is detected using a temperature detecting element. That is, when the detected temperature is equal to or higher than a predetermined temperature, it is determined that an open failure has occurred in the contact element. However, according to the above method, it is necessary to add an element for temperature detection and a circuit for temperature detection, which causes problems such as an increase in cost and an increase in mounting area. On the other hand, the inverter device 100 according to the second embodiment is realized with a simple configuration using the normally provided voltage detection unit 16 without adding the temperature detection element as described above. be able to.

  In the second embodiment, only the operation necessary for detecting the open failure of the contact element 15 by the charging circuit abnormality detection unit 17 has been described. However, the operation for determining the abnormality of the resistance value of the thermistor 14 described in the first embodiment and the operation for detecting an open fault may be used in combination. In that case, the process proceeds to step S24 in FIG. 5 after step S17 in FIG. That is, when the charging circuit abnormality detection unit 17 determines that the thermistor 14 is normal, the presence or absence of an open failure of the contact element 15 is detected. When both the operations are used together, an abnormality detection signal output when the charging circuit abnormality detecting unit 17 determines that the resistance value of the thermistor 14 is abnormal in step S18 of FIG. 2, and a charging circuit in step S29 of FIG. The abnormality detection unit 17 determines that an open failure has occurred in the contact element 15 and outputs the abnormality detection signal by changing the content or type of the signal so that the abnormality content can be distinguished.

  The charging circuit abnormality detection unit 17 and the inverter control unit 18 according to the first and second embodiments are specifically realized by a microcomputer or the like. FIG. 7 is a block diagram of the configuration of the microcomputer 200 according to the first and second embodiments. The functions of the charging circuit abnormality detection unit 17 and the inverter control unit 18 are realized by a microcomputer 200 having a configuration as shown in FIG. The microcomputer 200 includes a CPU (Central Processing Unit) 201 that performs calculation and control, a RAM (Random Access Memory) 202 that the CPU 201 uses as a work area, a ROM (Read Only Memory) 203 that stores programs and data, It includes an I / O (Input / Output) 204 that is hardware for exchanging signals with the outside, and a peripheral device 205 including an oscillator that generates a clock. The above-described abnormality detection method executed by the charging circuit abnormality detection unit 17 and the inverter control method executed by the inverter control unit 18 are realized by the CPU 201 executing a program stored in the ROM 203. The charging circuit abnormality detection unit 17 may be realized by a dedicated circuit instead of the microcomputer 200.

  As described above, according to the inverter device 100, during the initial charging operation of the smoothing capacitor 12, the voltage detector 16 detects the voltage before and after changing the contact signal to the contact element 15 from the off state to the on state. Thus, it is possible to obtain a voltage difference between the two and detect an abnormality in the resistance value of the thermistor 14 from the voltage difference. Further, when the inverter device 100 outputs a PWM signal, it is possible to detect an open failure of the contact element 15 by monitoring the interruption of the PWM signal and the repeated operation of the output. Thereby, the secondary failure caused by the failure of the charging circuit 20 can be prevented.

  The voltage detection unit that measures the voltage across the electrolytic capacitor and the current detection unit that measures the inrush current can be used to detect changes in the time constant of the voltage across the electrolytic capacitor that accompanies changes in the resistance value of the limiting resistor. A method for obtaining a change in time constant from the detected voltage and current by calculation is conceivable. The voltage detection unit is usually provided in an inverter device for control or overvoltage protection of an electrolytic capacitor, whereas a circuit needs to be added to provide the current detection unit. Furthermore, since the current detection unit needs to be provided in the main circuit unit that supplies current to the motor during the normal operation of the inverter device, the current detection element included in the current detection unit is increased in size, increasing the cost and mounting area. There is a problem. On the other hand, the inverter device 100 according to the first and second embodiments does not require the current detection unit, and can be realized with a simple configuration using a normally provided voltage detection unit.

  It is also conceivable to determine that the limiting resistance of the charging circuit is normal if the voltage across the electrolytic capacitor reaches a predetermined voltage. However, since the fluctuation of the input voltage range to the inverter device is widely accepted as about ± 20%, the method of judging the voltage between both ends with a predetermined voltage erroneously judges whether it is normal or abnormal. was there. However, in the inverter device 100 according to the first embodiment, after the power is turned on, the limiting resistance of the charging circuit is based on the voltage difference between the voltages across the smoothing capacitor 12 immediately before and after the contact signal is switched from the off state to the on state. Therefore, it is possible to determine the state of the charging circuit regardless of the input voltage.

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

  DESCRIPTION OF SYMBOLS 1 AC power supply, 2 Circuit breaker, 3 Electric motor, 11 Converter part, 12 Smoothing capacitor, 13 Inverter part, 14 Thermistor, 15 Contact element, 16 Voltage detection part, 17 Charging circuit abnormality detection part, 18 Inverter control part, 19 Display part 20 charging circuit, 21 DC bus, 100 inverter device, 200 microcomputer, 201 CPU, 202 RAM, 203 ROM, 204 I / O, 205 peripheral device.

Claims (6)

A converter unit for converting AC voltage into DC voltage;
A smoothing capacitor for smoothing the DC voltage output by the converter unit;
An inverter unit for converting a DC voltage smoothed by the smoothing capacitor into an AC voltage;
A parallel circuit in which a limiting resistor having a positive temperature characteristic or a resistance value increasing due to deterioration and a contact element whose opening or shorting is controlled by a contact signal are connected in parallel, the converter unit and the A charging circuit connected between the smoothing capacitor and
A voltage detection unit that detects a voltage across the smoothing capacitor and outputs a voltage detection signal;
Based on the voltage detection signal, when the voltage difference between the both-end voltages in a predetermined period including a time when the contact signal is switched so that the contact element is short-circuited from being opened is greater than a reference value, the restriction A detector that determines that the resistance value of the resistor is abnormal;
An inverter device comprising: A converter unit for converting AC voltage into DC voltage;
A smoothing capacitor for smoothing the DC voltage output by the converter unit;
An inverter unit for converting a DC voltage smoothed by the smoothing capacitor into an AC voltage;
A charging circuit connected between the converter unit and the smoothing capacitor, wherein the limiting resistor having a positive temperature characteristic and a contact element whose open or short circuit is controlled by a contact signal are connected in parallel. When,
A voltage detection unit that detects a voltage across the smoothing capacitor and outputs a voltage detection signal;
Based on the voltage detection signal, when the number of times that the voltage across the second threshold is equal to or higher than the first threshold and the second threshold that is a voltage value higher than the first threshold is equal to or higher than the specified number of times within a specified time. , A detection unit that determines that the contact element is an abnormality in which an open failure has occurred,
An inverter device comprising: An inverter control unit that generates a control signal for controlling the inverter unit;
3. The inverter device according to claim 1, wherein the inverter control unit does not output the control signal to the inverter unit when it is determined that the detection unit is abnormal. 4. Converter unit for converting AC voltage to DC voltage, smoothing capacitor for smoothing DC voltage output from converter unit, inverter unit for converting DC voltage smoothed by smoothing capacitor to AC voltage, and positive temperature A parallel circuit in which a limiting resistor having a characteristic or a characteristic in which a resistance value increases due to deterioration and a contact element whose open or short circuit is controlled by a contact signal are connected in parallel, the converter unit and the smoothing capacitor In an inverter device comprising: a charging circuit connected between the voltage detection unit; and a voltage detection unit that detects a voltage across the smoothing capacitor and outputs a voltage detection signal.
Based on the voltage detection signal, whether or not a voltage difference between the both-end voltages in a predetermined period including a time at which the contact signal is switched so that the contact element is short-circuited from being opened is equal to or less than a reference value. A determining step;
Determining that the resistance value of the limiting resistor is abnormal when the voltage difference is greater than the reference value;
An abnormality detection method for an inverter device, comprising: Converter unit for converting AC voltage to DC voltage, smoothing capacitor for smoothing DC voltage output from converter unit, inverter unit for converting DC voltage smoothed by smoothing capacitor to AC voltage, and positive temperature A parallel circuit in which a limiting resistor having characteristics and a contact element whose open or short circuit is controlled by a contact signal are connected in parallel, and a charging circuit connected between the converter unit and the smoothing capacitor; In an inverter device comprising: a voltage detection unit that detects a voltage across the smoothing capacitor and outputs a voltage detection signal;
Determining whether or not the number of times the voltage across the second threshold is equal to or greater than a second threshold, which is a voltage value higher than the first threshold after the voltage across the first threshold is equal to or greater than a specified number of times within a specified time;
A step of determining that the contact element has an open failure when the number of times is equal to or greater than the specified number of times within the specified time;
An abnormality detection method for an inverter device, comprising: The inverter device includes an inverter control unit that generates a control signal for controlling the inverter unit, and if it is determined to be abnormal, the inverter control unit does not output the control signal to the inverter unit. An abnormality detection method for an inverter device according to claim 4 or 5.

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