Device for controlling an electric motor

Abstract

Device (1) for controlling an electric motor with an anomaly detection function for a circuit part (4) which is connected between the device (1) for controlling the electric motor and the supply network (2), wherein the device (1) for controlling the electric motor comprises: a rectifier (11) into which alternating current power from the power source (2) is input via the circuit part (4) which is connected between the device (1) for controlling the electric motor and the supplying network (2) and which converts the alternating current power into direct current power; an inverter (12) that converts the direct current power from the rectifier (11) into alternating current power; a DC link capacitor (13) which is provided for a DC connection between the rectifier (11) and the inverter (12); a voltage detection section (14) that detects the voltage of the intermediate circuit capacitor (13); and an anomaly detection part (16) which receives a voltage change amount of the intermediate circuit capacitor (13) per unit of time on the basis of voltage values ​​detected by the voltage detection part (14) and performs an anomaly detection on the basis of the voltage change amount thus obtained to the circuit part (4) which is connected between the device (1) for controlling the electric motor and the supply network (2).

Description

BACKGROUND OF THE INVENTION Area of ​​the invention

[0001] The present invention relates to a device for controlling an electric motor with an anomaly detection function in a circuit part that is connected between the device for controlling an electric motor and the AC power source. Related area

[0002] A device for controlling an electric motor is known, which controls the motors in machine tools, industrial machines, stretch rolling machines, injection molding machines or various robots. Fig. Figure 2 is a view showing an example of such a device for controlling an electric motor. The in Fig. The device IX shown in Figure 2, for controlling an electric motor, comprises a rectifier 11, which converts three-phase AC power from an AC power source 2 into DC power, and an inverter 12, which converts the DC power from the rectifier 11 into three-phase AC power and supplies the three-phase AC power to a motor 3. A DC link capacitor 13 is provided between the rectifier 11 and the inverter 12 for a DC connection.

[0003] Patent documents 1 to 3 disclose a technology for such a device for controlling an electric motor that detects anomalies in its own device. Patent document 1 describes a technology that disconnects a short-circuit bus connecting the DC link unit and the inverter unit (which is connected to the inverter 12 in Fig. 2 corresponds) connects, detected.

[0004] Furthermore, patent document 2 describes a technology that detects anomalies in its own device based on the applied voltage or the flowing electric current. In addition, patent document 2 describes the subject matter of blocking the activation of its own device based on the cumulative frequency of anomaly occurrences and / or the peak voltage applied to its own device or the peak electric current flowing in its own device, and / or the time course of this peak voltage or peak electric current, thereby preventing secondary damage to a peripheral component of its own device.

[0005] Furthermore, patent document 3 describes a technology that can prevent a defect caused by an electrical short circuit in a rectifier diode (which is connected to rectifier 11 in Fig. 2 corresponds) detected. Furthermore, patent document 3 describes the subject matter of detecting the loss of only one phase in three-phase AC power by differentiating it from the short-circuit defect of the rectifier diode.

[0006] Patent document 4 relates to a motor drive device comprising: a converter unit configured to convert an alternating voltage into a direct voltage; a DC link unit configured to smooth the direct voltage through a capacitor to generate a DC link voltage; several inverter units configured to convert the DC link voltage into a multi-phase alternating voltage for motor drive; several short-circuit rails configured to electrically connect terminals of the DC link unit and terminals of the several inverter units to each other;a DC link voltage detection unit configured to detect the DC link voltage, wherein the DC link voltage detection unit is located on an inverter unit of a last stage, such that the multiple short-circuit rails are located between the terminals of the DC link unit and the terminals of the DC link voltage detection unit. Patent document 1: Japanese unexamined patent application publication JP 2015-14566A Patent document 2: Japanese unexamined patent application publication JP 2016-100977A Patent document 3: Japanese unexamined patent application publication JP 2015-46962A Patent document 4: US 2015 / 0 229 246 A1 SUMMARY OF THE INVENTION

[0007] As in Fig. However, as shown in Figure 2, a device such as a circuit breaker 5A and / or an electromagnetic contactor 5B may be provided for the circuit section that is connected between the device for controlling an electric motor and the AC power source at an earlier stage than the device IX for controlling an electric motor (i.e., in the circuit section 4 between the device IX for controlling an electric motor and the AC power source 2).

[0008] In this case, the AC power from the AC power source 2 cannot be supplied to the device IX for driving an electric motor due to a defect in device 5. In this case, the device IX for driving an electric motor detects the defect in device 5 as a defect in its own device. For example, the device IX for driving an electric motor detects the defect in device 5 as a voltage drop in the DC link capacitor 13 of its own device during motor acceleration. Furthermore, the device IX for driving an electric motor detects the defect in device 5 as a voltage rise in the DC link capacitor 13 of its own device during motor deceleration.

[0009] In this way, with the conventional device IX for controlling an electric motor, it is not possible to detect a defect in the device 5 (i.e., an anomaly in the circuit part 4) provided for the circuit part 4 between the device IX for controlling an electric motor and the AC power source 2. It is noted that the devices for controlling an electric motor described in patent documents 1 to 3 also do not detect a defect in the device provided for the circuit part 4 between the device for controlling an electric motor and the AC power source.

[0010] Thus, the present invention has an objective of providing a device for controlling an electric motor that can detect anomalies in the circuit part that is connected between the device for controlling an electric motor and the AC power source.

[0011] (1) A device for controlling an electric motor (e.g., the device 1 for controlling an electric motor described below) according to the present invention is a device for controlling an electric motor with an anomaly detection function for a circuit part connected between the device for controlling an electric motor and the AC power source (e.g., the circuit part 4 described below) between its own device and a power source (e.g., the AC power source 2 described below), wherein the device for controlling an electric motor includes: a rectifier (e.g., the rectifier 11 described below), into which AC power is input from the power source via the circuit part 4 and which converts the AC power into DC power; an inverter (e.g.,the inverter 12 (described later), which converts the DC power from the rectifier into AC power; an intermediate circuit capacitor (e.g., the intermediate circuit capacitor 13 described later), which is provided for a DC connection between the rectifier and the inverter; a voltage detection section (e.g., the voltage detection section 14 described later), which detects the voltage of the intermediate circuit capacitor; and an anomaly detection section (e.g., the anomaly detection section 16 described later), which, based on voltage values ​​detected by the voltage detection section, obtains a voltage change value of the intermediate circuit capacitor for a predetermined time and, based on the voltage change value thus obtained, performs anomaly detection at the circuit section 4.

[0012] (2) In the device described in (1) for controlling an electric motor, the amount of voltage change can be an amount of voltage change per unit of time.

[0013] (3) The device for controlling an electric motor described in (1) or (2) may further include a storage part (e.g. the storage part 15 described below) which stores in advance a threshold value for detecting an anomaly of the circuit part 4, wherein the anomaly detection part can detect that the circuit part 4 is anomalous if the voltage change magnitude is greater than the threshold value.

[0014] (4) In the device described in (3) for controlling an electric motor, the memory component may enable the external rewriting of the threshold value.

[0015] According to the present invention, it is possible to create a device for controlling an electric motor that can detect anomalies in the circuit part 4. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a view showing a circuit configuration of a device for controlling an electric motor according to an embodiment of the present invention; and Fig. Figure 2 is a view showing a circuit configuration of a conventional device for controlling an electric motor. DETAILED DESCRIPTION OF THE INVENTION

[0016] An example of an embodiment of the present invention is explained below with reference to the drawings. It should be noted that identical or corresponding sections in the respective drawings are marked with the same reference numerals. (First embodiment)

[0017] Fig. Figure 1 is a view showing a circuit configuration of a device for controlling an electric motor according to a first embodiment of the present invention. The Fig. The device 1 shown for controlling an electric motor inputs three-phase AC power from a commercially available three-phase AC power source 2 to drive a motor 3. It is noted that the AC power source 2 is not limited to three-phase AC and can, for example, be single-phase AC.

[0018] For a circuit section 4 between the device 1 for controlling an electric motor and the AC power source 2, a device 5 such as a circuit breaker 5A and an electromagnetic contactor 5B is provided.

[0019] The device 1 for controlling an electric motor contains a rectifier 11, an inverter 12, a DC link capacitor 13, a voltage detection part 14, a storage part 15 and an anomaly detection part 16.

[0020] The rectifier 11 converts the AC power from the AC power source 2 into DC power. The DC converter 11 is configured, for example, as a diode rectifier converter or as a PWM converter with a bridge circuit of power semiconductor devices and diodes connected in reverse parallel to the power semiconductor devices.

[0021] Inverter 12 converts the DC power from rectifier 11 into AC power and supplies this AC power to motor 3. Inverter 12 is configured, for example, as a bridge circuit with power semiconductor devices and diodes connected in reverse parallel to the power semiconductor devices. Inverter 12 converts the DC voltage into an AC voltage with a desired waveform and frequency by switching these power semiconductor devices on and off (e.g., PWM control) in accordance with commands from the control unit (not shown).

[0022] Furthermore, the inverter 12 converts the AC power recovered from the motor 3 into DC power and supplies this DC power to a DC connection between the inverter 12 and the rectifier 11.

[0023] The DC link capacitor 13 is provided for the DC connection between the rectifier 11 and the inverter 12. The DC link capacitor 13 stores the DC power from the rectifier 11 and the DC power (recovery power) from the inverter 12. Furthermore, the DC link capacitor 13 smooths the DC voltage converted by the rectifier 11 or by the inverter 12.

[0024] The voltage detection section 14 is connected in parallel to the intermediate circuit capacitor 13 and detects the voltage between both terminals of the intermediate circuit capacitor 13. It is possible, for example, to use an existing voltage detection circuit as the voltage detection section 14.

[0025] Memory section 15 stores a threshold value in advance for detecting a defect in device 5 (i.e., an anomaly in circuit section 4). More precisely, memory section 15 stores a threshold value in advance for detecting a sudden voltage change in the intermediate circuit capacitor 13 caused by a defect in device 5.

[0026] The threshold is set, for example, based on the magnitude of the voltage change per unit time, taking into account the energy stored in the DC link capacitor 13 and the energy required for the acceleration / deceleration operation of the motor 3. More precisely, the magnitude of the voltage change in the DC link capacitor 13 is first determined if the acceleration energy to the motor 3 is supplied solely by the DC link capacitor 13, or if the deceleration energy from the motor 3 is absorbed solely by the DC link capacitor 13, and this value is then set as the approximate estimate for the threshold.

[0027] Memory module 15 is a rewritable memory such as an EEPROM. This allows memory module 15 to rewrite the threshold value using an external device such as a computer. Memory module 15 also stores predefined software (a predefined program) for implementing the various functions of the anomaly detection module 16.

[0028] The anomaly detection section 16 receives a voltage change per unit time value of the DC link capacitor 13 based on the voltage values ​​detected by the voltage detection section 14. Based on this voltage change value, the anomaly detection section 16 performs a fault detection for the device 5 (i.e., an anomaly detection of the circuit section 4). More precisely, the anomaly detection section 16 detects that the device 5 is faulty (i.e., that the circuit section 4 is anomalous) if the received voltage change value is greater than the threshold value in the memory section 5.

[0029] The anomaly detection section 16 is configured, for example, by an arithmetic processor such as a DSP (digital signal processor) or an FPGA (free programmable logic array). The functions of the anomaly detection section 16 are implemented by executing predefined software (programs) stored in the memory section 15. The functions of the anomaly detection section 16 can be implemented through interaction between hardware and software, or solely through hardware (electronic circuits).

[0030] The defect detection operation for the device 5 (i.e., the anomaly detection operation of the circuit part 4) by the device 1 for controlling an electric motor is explained below.

[0031] Initially, a major portion of the acceleration energy required during the acceleration of motor 3 is supplied by the AC power source 2, assuming the device 5 is operating normally. Furthermore, most of the deceleration energy generated during the deceleration of motor 3 is recovered in the AC power source 2.

[0032] Subsequently, the acceleration energy of motor 3 is supplied by the intermediate circuit capacitor 13 only when motor 3 is being accelerated, if the AC power from the AC power source 2 of the device IX for driving an electric motor is no longer supplied due to a defect in the device 5. However, the voltage of the intermediate circuit capacitor 13 drops immediately, since the capacitance of the intermediate circuit capacitor 13 is generally small compared to the power supply capacitance.

[0033] The anomaly detection section 16 detects a defect in device 5 (i.e., an anomaly in circuit part 4) based on the magnitude of the voltage change (the magnitude of the voltage drop) that is steep at that time. More precisely, based on the voltage values ​​detected by the voltage detection section 14, the anomaly detection section 16 obtains the magnitude of the voltage change (magnitude of the voltage drop) per unit time of the DC link capacitor 13 and detects that device 5 is defective (i.e., that circuit part 4 is anomalous) if the obtained magnitude of the voltage change is greater than the threshold value in the memory section 15.

[0034] On the other hand, the deceleration energy of motor 3 is only stored in the DC link capacitor 13 if the AC power from the AC power source 2 to the device IX for driving an electric motor is no longer supplied due to a defect in the device 5, if the deceleration (recovery) of motor 3 is performed. As mentioned above, however, the voltage of the DC link capacitor 13 rises immediately, since the capacitance of the DC link capacitor 13 is small compared to the power supply capacitance.

[0035] The anomaly detection section 16 detects a defect in device 5 (i.e., an anomaly in circuit part 4) based on the magnitude of the voltage change (the magnitude of the voltage rise) that is steep at that time. More precisely, based on the voltage values ​​detected by the voltage detection section 14, the anomaly detection section 16 obtains the magnitude of the voltage change (magnitude of the voltage rise) per unit time of the DC link capacitor 13 and detects that device 5 is defective (i.e., that circuit part 4 is anomalous) if the obtained magnitude of the voltage change is greater than the threshold value in the memory section 15.

[0036] As explained above, according to the device 1 for driving an electric motor of the present embodiment, it is possible to detect a condition in which the AC power is no longer supplied to the device 1 for driving an electric motor by the AC power source 2, i.e., a defect of the device 5 (i.e., an anomaly of the circuit part 4 between the device 1 for driving an electric motor and the AC power source 2), based on the steep voltage change amount (voltage drop amount) per unit time of the DC link capacitor 13 during the deceleration of the motor 3.

[0037] However, regardless of whether device IX for controlling an electric motor is functioning normally, the maintenance provider will incorrectly identify device IX for controlling an electric motor as defective if the defect of device 5 is as described in the Fig. The conventional device IX shown in Figure 2, used to control an electric motor, is detected as having a defect in its own device. As a result, the maintenance provider would initiate a defect investigation of the device IX, thus wasting time specifying the actual cause of the defect. Furthermore, during this time, the machine's operating rate would decrease because the operation of the machinery controlled by the device IX would be suspended.

[0038] Furthermore, the service provider can replace device IX for controlling an electric motor if they are unable to determine the cause of the defect. However, the labor involved in such maintenance is uneconomical, as the device for controlling an electric motor is a standard component.

[0039] In contrast, according to the device 1 for controlling an electric motor of the present embodiment, the maintenance provider can quickly detect and resolve a defect in the device 5 (i.e., an anomaly in the circuit part 4), so that no time is required to specify the actual cause of the defect. As a result, it is possible to prevent a reduction in the operating rate of a machine controlled by the device 1 for controlling an electric motor.

[0040] Furthermore, according to the device 1 for controlling an electric motor of the present embodiment, a normal device for controlling an electric motor is not replaced, so that it is possible to reduce the workload of the maintenance.

[0041] Since the threshold value in the device 1 for controlling an electric motor of the present embodiment can also be rewritten by an external device, the device 1 for controlling an electric motor can change the threshold value to a suitable value, even after the value has been set once. (Second embodiment)

[0042] In the first embodiment, a defect in the device 5 (an anomaly in the circuit section 4, which is connected between the device 1 for controlling an electric motor and the AC power source 2) is detected during acceleration or deceleration of the motor 3 based on the voltage change per unit time of the DC link capacitor 13. In the second embodiment, a defect in the device 5 (an anomaly in the circuit section 4) is also detected during operation at a constant speed of the motor 3, in addition to during acceleration or deceleration of the motor 3, based on the voltage change per unit time of the DC link capacitor 13.

[0043] The configuration of device 1 for controlling an electric motor according to the second embodiment is the same as that described in Fig.The configuration of the device 1 for controlling an electric motor according to the first embodiment is shown in Figure 1. It is noted that the device 1 for controlling an electric motor according to the second embodiment differs from the device 1 for controlling an electric motor according to the first embodiment with regard to the functions and operation of the anomaly detection part 16 and the threshold stored in the memory part 15.

[0044] The memory section 15 stores in advance the threshold for detecting the voltage change of the DC link capacitor 13 for a predetermined time caused by a defect in the device 5 (i.e., by an anomaly in the circuit section 4). The threshold is set based on the magnitude of the voltage change per unit time, which is determined by the energy stored in the DC link capacitor 13 and the energy required for constant-speed operation of the motor 3. More precisely, the magnitude of the voltage change of the DC link capacitor 13 is determined for the case where the energy required for constant-speed operation is supplied to the motor 3 solely by the DC link capacitor 13 for a predetermined time, and this value is set as the approximate estimate for the threshold.

[0045] The anomaly detection section 16 receives the voltage change magnitude of the intermediate circuit capacitor 13 for a predetermined time based on the voltage values ​​detected by the voltage detection section 14. The anomaly detection section 16 performs the fault detection of the device 5 (i.e., the anomaly detection of the circuit section 4) based on the received voltage change magnitude. More precisely, the anomaly detection section 16 detects that the device 5 is faulty (i.e., that the circuit section 4 is anomalous) if the received voltage change magnitude is greater than the threshold value in the memory section 15.

[0046] The following explains the defect detection operation for the device 5 by the device 1 for controlling an electric motor (i.e., by the anomaly detection operation for the circuit part 4).

[0047] If the AC power from the AC power source 2 of the device IX for driving an electric motor is no longer supplied due to a defect in the device 5, the energy required for operation at constant speed of the motor 3 will be supplied only by the DC link capacitor 13, even during operation at constant speed of the motor 3. Simultaneously, the voltage of the DC link capacitor 13 drops according to the motor load.

[0048] The anomaly detection section 16 detects a defect in device 5 (i.e., an anomaly in circuit part 4) simultaneously based on the voltage change magnitude (voltage drop magnitude) for a predetermined time. More precisely, based on the voltage values ​​detected by the voltage detection section 14, the anomaly detection section 16 receives the voltage change magnitude (voltage drop magnitude) of the DC link capacitor 13 for a predetermined time and detects that device 5 is defective (i.e., that circuit part 4 is anomalous) if the received voltage change magnitude is greater than the threshold value in the memory section 15.

[0049] It is noted that it is possible to detect that device 5 is defective (i.e., that circuit part 4 is anomalous) because a steeper voltage change occurs during acceleration and deceleration of motor 3. Since these operations are the same as in the first embodiment, further explanation is omitted.

[0050] With this device 1 for controlling an electric motor of the second embodiment, it is also possible to obtain similar effects as in the first embodiment.

[0051] Furthermore, according to the device 1 for controlling an electric motor of the second embodiment, it is possible to detect a defect of the device 5 (i.e. an anomaly of the circuit part 4 between the device 1 for controlling an electric motor and the AC power source 2) not only during acceleration and deceleration of the motor 3, but also during operation at constant speed of the motor 3.

[0052] For example, in the embodiments mentioned above, the anomaly detection part 16 detects a defect in the device 5 (i.e., an anomaly in the circuit part 4 between the device 1 for driving an electric motor and the AC power source 2) by comparing the received voltage change magnitude with a pre-stored threshold value; however, the present invention is not intended to be limited to this. For example, the anomaly detection part 16 can detect a defect in the device 5 (i.e., an anomaly in the circuit part 4) when the voltage value changes (when it decreases or increases).

[0053] Furthermore, the defect detection of the device 5, such as the circuit breaker 5A and the electromagnetic contactor 5B, which are provided in the circuit section 4, is illustrated in the embodiments mentioned above as the anomaly detection of the circuit section 4 between the device 1 for controlling an electric motor and the AC power source 2. However, the present invention is not intended to be limited to this and it is also possible to apply it to the defect detection of devices such as a power transformer provided in the circuit section 4 or to the separation detection in an element such as a cable. EXPLANATION OF REFERENCE MARKS 1, 1X Device for controlling an electric motor 2 AC power sources 3 Engine 4. Circuit section that is connected between the device for controlling an electric motor and the AC power source. 5 Setup 5A circuit breaker 5B electromagnetic contactor 11 Rectifiers (forward converters) 12 Inverters (Reverse Inverters) 13 Intermediate circuit capacitor (DC connection capacitor) 14 Voltage detection section 15 Memory section 16 Anomaly Detection Section

Claims

[1] Device (1) for controlling an electric motor with an anomaly detection function for a circuit part (4) which is connected between the device (1) for controlling the electric motor and the supply network (2), wherein the device (1) for controlling the electric motor comprises: a rectifier (11) into which alternating current power from the power source (2) is input via the circuit part (4) which is connected between the device (1) for controlling the electric motor and the supplying network (2) and which converts the alternating current power into direct current power; an inverter (12) that converts the direct current power from the rectifier (11) into alternating current power; a DC link capacitor (13) which is provided for a DC connection between the rectifier (11) and the inverter (12); a voltage detection section (14) that detects the voltage of the intermediate circuit capacitor (13); and an anomaly detection part (16) which receives a voltage change amount of the intermediate circuit capacitor (13) per unit of time on the basis of voltage values ​​detected by the voltage detection part (14) and performs an anomaly detection on the basis of the voltage change amount thus obtained to the circuit part (4) which is connected between the device (1) for controlling the electric motor and the supply network (2). [2] Device (1) for controlling an electric motor according to claim 1, which further comprises a storage part (15) which stores in advance a threshold value for detecting an anomaly of the circuit part (4) which is connected between the device (1) for controlling the electric motor and the supplying network (2), wherein the anomaly detection part (16) detects that the circuit part (4) which is connected between the device (1) for controlling the electric motor and the supplying network (2) is anomalous if the voltage change magnitude is greater than the threshold value. [3] Device (1) for controlling an electric motor according to claim 2, wherein the memory part (15) enables the external rewriting of the threshold value.

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