Motor control device

Abstract

The present application provides a kind of motor control device, the motor control device includes: converter part, power from power supply as direct current power output;Capacitor part, keep the direct current power;And inverter part, the direct current power is converted into alternating current power, and drive motor, the motor control device further includes: impact current prevention circuit part, between the converter part and the capacitor part, with the anti-impact resistor of inhibiting the impact current in the charging of the capacitor part and anti-impact switch;And anti-impact resistance protection part, protects the anti-impact resistor, the anti-impact resistance protection part calculates the power through the anti-impact resistor, calculates the short time electric quantity of specified time period, and based on the short time electric quantity of specified time period, generates the information of the degradation amount of the anti-impact resistor and informs the degradation amount to outside.

Description

Technical Field

[0001] One aspect of the present invention relates to an electric motor control device. Background Technology

[0002] In this motor control device, when driving the motor, a converter transforms the three-phase AC voltage into DC voltage, a smoothing capacitor smooths the DC voltage, and an inverter converts the smoothed DC voltage back into three-phase AC voltage. In this motor control device, an electromagnetic contactor is installed between the three-phase AC power supply and the motor control device to cut off the power supply in case of an abnormality in the motor control device.

[0003] Furthermore, when driving the motor control device, the electromagnetic contactor is first turned on to connect the three-phase AC power supply to the motor control device. Since a smoothing capacitor is installed in the motor control device, an inrush current flows to charge the smoothing capacitor when the power is turned on. Due to the low impedance of the smoothing capacitor, a large inrush current flows, which may damage the rectifier diodes constituting the converter. To suppress this, an inrush current prevention circuit, including a resistor and an electromagnetic contactor (anti-inrush MS), is sometimes installed at the output of the converter. In this case, the smoothing capacitor is charged through the resistor when the power is turned on. After the smoothing capacitor is charged, the anti-inrush MS turns on, and the motor is driven. Additionally, a discharge resistor is sometimes provided to discharge the voltage of the smoothing capacitor after the power is cut off. In this case, the voltage of the smoothing capacitor is discharged after the power is cut off, thus ensuring the safety of maintenance operations.

[0004] Such a method for protecting against surge current is described in Japanese Patent Publication No. 2017-5973. The technology described in this document relates to a multi-axis motor control device comprising a converter section and multiple inverter sections. The converter section includes a rectifier circuit and a surge current prevention circuit. The inverter section includes a smoothing capacitor and an inverter circuit. This technology avoids the risk of surge current breakage when the number of inverter sections increases.

[0005] The motor drive device described in Japanese Patent Publication No. 2017-5973 includes: a rectifier circuit, an inverter section, an initial charging section, a storage section, a power calculation section, and a switching section. The rectifier circuit rectifies the alternating current supplied from the AC power supply side and outputs a direct current to the DC-LINK, which serves as the DC side. The inverter section has a smoothing capacitor on the DC-LINK side connected to the rectifier circuit. The inverter section converts the direct current from the rectifier circuit and outputs an alternating current for motor drive. The initial charging section is provided at the DC-LINK. The initial charging section has a switch and a charging resistor connected in parallel with the switch. During the initial charging period before motor drive begins, the initial charging section utilizes the direct current from the rectifier circuit flowing through the charging resistor by opening the switch to perform initial charging until the smoothing capacitor reaches a predetermined voltage. The storage section stores the resistance value of the charging resistor and a pre-defined load capacity as the amount of electricity required to melt the charging resistor. The power calculation unit calculates the average charge generated in the charging resistor over a certain time interval due to the flow of DC current from the rectifier circuit. During the initial charging period, if the average charge calculated by the power calculation unit reaches the load capacity, the switching unit cuts off the flow of DC current from the rectifier circuit into the smoothing capacitor. After this cutoff, if the average charge calculated by the power calculation unit is below a predetermined threshold, the switching unit allows the DC current from the rectifier circuit to flow into the smoothing capacitor.

[0006] In the device described in Japanese Patent Publication No. 2017-5973, the load capacity is set to the amount of electricity required to melt the charging resistor. Relatedly, the charging resistor has a lifespan. With small amounts of electricity, the charging resistor has a long lifespan. With large amounts of electricity, the charging resistor's lifespan becomes shorter.

[0007] [Table 1]

[0008] 100,000 1400 26 50,000 1520 28 20,000 1690 31 10,000 1810 33 5,000 1930 39 2,000 2090 42 1,000 2220 49 100 2620 75 10 3030 87 1 3440 98

[0009] Table 1 shows an example of the lifespan, energy (charge), and permissible repetition time of an anti-surge resistor. When the expected lifespan of the anti-surge resistor is 100,000 cycles, the energy applied to the anti-surge resistor is 1400J or less. However, when the anti-surge resistor is used with 2220J of energy applied to it for a short period, the lifespan decreases to 1000 cycles. Furthermore, if more than 3440J of energy is applied to the anti-surge resistor for a short period, the resistor breaks. Therefore, according to the concept in Japanese Patent Publication No. 2017-5973, when a small charge that meets the product lifespan is set as the load capacity of the charging resistor, if the average charge calculated by the power calculation unit during a single charge reaches a small charge, the DC current from the rectifier circuit flowing into the smoothing capacitor is cut off. Furthermore, if the average charge calculated by the power calculation unit is below a specified threshold, the DC current from the rectifier circuit flows into the smoothing capacitor.

[0010] However, when the capacitance of the smoothing capacitor is large, the flow to the smoothing capacitor is interrupted several times during a single initial charge. Therefore, if the average current of the charging resistor at the time of flow interruption is not suppressed to below the allowable value, the surge protector may break. Even when the average current of the charging resistor at the time of flow interruption is suppressed to below the allowable value, the flow interruption interval becomes a long time, such as tens of seconds. Therefore, the time required for initial charging increases, and the start-up time of the system constituting the motor control device is prolonged. If the start-up time is prolonged, the efficiency of the machine decreases. Therefore, it is desirable not to prolong the start-up time. If a relatively large amount of current is set as the load capacity to suppress the prolongation of the start-up time, the start-up time of the system is shortened, but the product durability is insufficient. Therefore, the surge protector is prone to breakage due to deterioration. Furthermore, in the case of a momentary power outage when the power is switched on, and when a small amount of current with a sufficiently long product lifespan is set as the load capacity, the start-up time of the system further increases. On the other hand, when a relatively large amount of current is set as the load capacity, the surge protector is prone to breakage due to deterioration because of insufficient product lifespan. Furthermore, when a small electrical charge is set as the load capacity to significantly extend the product's lifespan, the switching section is repeatedly opened and closed. As a result, the lifespan of the electromagnetic contactor constituting this switching section is reduced.

[0011] Furthermore, unlike the device in Japanese Patent Publication No. 2017-5973, it is also possible to detect an alarm and disconnect the electromagnetic contactor when the average electrical charge calculated by the power calculation unit reaches the load capacity. In this case, alarms are detected frequently when the load capacity is set to a small amount, thus increasing the system downtime. Furthermore, when the load capacity is set to a relatively large amount, although it is difficult to generate an alarm, the surge protector is prone to breakage due to the accumulation of deterioration. Summary of the Invention

[0012] One object of the present invention is to provide a motor control device that includes a function for monitoring the degradation of an anti-surge resistor. This motor control device can suppress frequent alarm detections, prolonged device start-up time, and reduced lifespan of the electromagnetic contactor at the power input section. Furthermore, this motor control device can prevent the anti-surge resistor from deteriorating and breaking due to power generated during operation of the motor control device, thus preventing the motor control device from stopping.

[0013] An electric motor control device according to one aspect of the present invention includes: a converter section connected to an input switch section that can be connected to a power source and outputs power from the power source as DC power; a capacitor section that holds the DC power; and an inverter section that converts the DC power into AC power and drives an electric motor, wherein the input switch section, the converter section, the capacitor section, and the inverter section are connected in this order. The electric motor control device further includes: an inrush current prevention circuit section disposed between the converter section and the capacitor section, having an inrush current prevention resistor and an inrush current prevention switch for suppressing inrush current during charging of the capacitor section; and an inrush current prevention resistor protection section that protects the inrush current prevention resistor, wherein the inrush current prevention resistor protection section calculates the power passing through the inrush current prevention resistor, calculates a short-term power consumption during a predetermined time period, and generates information on the degradation amount of the inrush current prevention resistor based on the short-term power consumption during the predetermined time period and notifies the externally of the degradation amount.

[0014] Furthermore, the surge protector unit may calculate the alarm charge of the surge protector by accumulating power when voltage is applied to the surge protector and subtracting a predetermined value from the accumulated power when no voltage is applied to the surge protector. If the alarm charge reaches a predetermined threshold (a value higher than the charge required to satisfy the product's durability cycles), the inverter unit may be stopped and the input switch unit may be disconnected.

[0015] Alternatively, the surge protection unit may calculate the number of durability cycles corresponding to the short-term charge based on the short-term charge and the specifications of the surge protection resistor, calculate the deterioration sum value (ΔD) by calculating the reciprocal of the number of durability cycles corresponding to the short-term charge, and obtain the deterioration amount by adding the deterioration sum value to the previous deterioration amount.

[0016] In addition, the surge protection unit may calculate the short-term charge of the surge protection resistor by accumulating the power applied to the surge protection resistor from the start of voltage application to the surge protection resistor until a certain period of time has elapsed.

[0017] In addition, when the alarm power reaches the specified threshold, the surge protection unit may stop the inverter's drive and notify the outside of the surge protection resistor's overload abnormality.

[0018] Furthermore, the power of the surge current prevention circuit section's surge resistor can be calculated based on the voltage or current of the power, which can at least be approximated.

[0019] Furthermore, the power of the surge current prevention circuit section's surge current prevention resistor can be calculated based on the voltage of the capacitor section, the output voltage of the converter section, and the resistance value of the surge current prevention resistor.

[0020] According to one aspect of the present invention, a motor control device including a degradation monitoring function for an anti-surge resistor is provided. In this motor control device, the overload anomaly detection threshold for the anti-surge resistor is set to a value higher than the electrical charge required to satisfy the product's durability cycle. Furthermore, a degradation amount corresponding to a short-term electrical charge value is calculated, and preventative maintenance is performed using this degradation amount. This suppresses frequent alarm detections, prolonged device start-up time, and reduced lifespan of the electromagnetic contactor at the power input section. Moreover, this motor control device can prevent the motor control device from stopping due to wire breakage caused by anti-surge resistor degradation during operation. Attached Figure Description

[0021] Figure 1 This is a circuit diagram of a motor control device according to one embodiment of the present invention.

[0022] Figure 2 This is a control flowchart of an electric motor control device according to one embodiment of the present invention.

[0023] Figure 3 This is a graph illustrating the relationship between short-term battery charge and the number of battery cycles.

[0024] Figure 4This is a graph illustrating the relationship between the sum of short-term power consumption and degradation.

[0025] Figure 5A It is a graph that shows an example of the changes in the electrical power of various parts when a normal power source is turned on.

[0026] Figure 5B It is a graph that shows an example of the changes in the electrical properties of various parts when a momentary power outage occurs while the power is on.

[0027] Figure 5C This is a graph illustrating the changes in electrical quantities and other parameters of various components when two momentary power outages occur during power-on. Detailed Implementation

[0028] In the following detailed description, numerous specific details are presented for illustrative purposes and to provide a thorough understanding of the disclosed embodiments. However, it will be apparent that one or more embodiments can be implemented without these specific details. In other instances, well-known structures and apparatuses are shown schematically for the purpose of simplifying the drawings.

[0029] Figure 1 This illustrates one embodiment of the present invention. The motor control device 10 includes: a converter section 20, an inrush current prevention circuit section 30, a regenerative resistor 50 and a regenerative resistor driving transistor 51, a smoothing capacitor C (capacitor section), and an inverter section 70, which are arranged in this order starting from the three-phase AC power supply S, which serves as the power source.

[0030] The converter unit 20 is connected to an electromagnetic contactor EC (input switch unit) that can be connected to a three-phase AC power supply S, and outputs power from the three-phase AC power supply S as DC power. The converter unit 20 includes six rectifier diodes 21 for full-wave rectification. A smoothing capacitor C holds the DC power.

[0031] The inverter unit 70 includes six semiconductor switches 71 that convert the DC power into AC power. The inverter unit 70 converts the DC power into AC power and drives the motor.

[0032] An inrush current prevention circuit 30 is provided between the converter section 20 and the smoothing capacitor C. The inrush current prevention circuit 30 includes an anti-inrush resistor R that suppresses inrush current during the charging of the smoothing capacitor C, and an anti-inrush magnetic switch (hereinafter referred to as "anti-inrush MS") that serves as an anti-inrush switch, which are connected in parallel. A regenerative resistor drive transistor 51 controls the operation of the regenerative resistor 50.

[0033] Furthermore, the motor control device 10 is equipped with an anti-surge resistor protection unit 80 to protect the anti-surge resistor R. The anti-surge resistor protection unit 80 calculates the power passing through the anti-surge resistor R, calculates the short-term power consumption during a specified time period, and generates information on the degradation amount of the anti-surge resistor R based on the short-term power consumption during the specified time period and notifies the outside of the degradation amount.

[0034] Furthermore, the surge protection unit 80 calculates the power of the surge protection resistor R of the surge current prevention circuit unit 30 based, for example, the voltage of the smoothing capacitor C (DC voltage VDC), the output voltage of the converter unit 20 (DC output voltage VDCI), and the resistance value of the surge protection resistor R (resistance value R).

[0035] Furthermore, the surge protection unit 80 calculates the number of durability cycles corresponding to the short-term charge Ws based on the specifications of the surge protection resistor R, for example, and calculates the sum of the degradation values ​​by calculating the reciprocal of the number of durability cycles corresponding to the short-term charge Ws. The degradation value is then obtained by adding this degradation value to the previous degradation value.

[0036] Furthermore, the surge protection unit 80 calculates the short-term charge of the surge protection resistor R by accumulating the charge applied to the surge protection resistor R from the start of voltage application to the surge protection resistor R until a certain period of time has elapsed.

[0037] The surge protection unit 80 obtains (calculates) the electrical charge (power through the surge protector) of the surge protector R and performs the necessary control to protect the surge protector R.

[0038] Here, a three-phase AC power supply S is used as the power source for the motor control device 10. An electromagnetic contactor EC (input switch section) is connected between the three-phase AC power supply S and the motor control device 10. Furthermore, the output of the inverter section 70 of the motor control device 10 is connected to the motor M.

[0039] When the motor M is driven, the electromagnetic contactor EC is turned on. As a result, the power supply voltage is rectified by the converter section 20 and converted into a DC voltage. Furthermore, while suppressing inrush current through the surge resistor R, the smoothing capacitor C is charged.

[0040] After the smoothing capacitor C finishes charging, the surge protector MS turns on, and the inverter section 70 generates an AC voltage. This AC voltage drives the motor M. When the motor M is running, power is supplied to the motor M from the three-phase AC power supply S through the converter section 20 and the inverter section 70.

[0041] During regenerative operation of the motor M, power is supplied from the motor M to the smoothing capacitor C through the inverter section 70 to charge the smoothing capacitor C. When the DC voltage is higher than the reference value, the regenerative resistor drive transistor 51 is turned on; conversely, when the DC voltage is lower than the reference value, the regenerative resistor drive transistor 51 is turned off. Thus, the DC voltage is controlled within a certain range.

[0042] Furthermore, when the operation of the motor M is stopped, the inverter section 70 is disconnected, and the electromagnetic contactor EC is disconnected.

[0043] When the input voltage of the motor control device 10 decreases, the regenerative resistor drive transistor 51 is turned on, and the charge in the smoothing capacitor C is discharged. In this embodiment, an example is shown where the regenerative resistor is also used as a discharge resistor. Furthermore, how the regenerated power is discharged or how it is utilized is arbitrary.

[0044] The surge protection unit 80 detects the DC output voltage VDCI of the converter unit 20 and the DC voltage VDC of the smoothing capacitor C, as described later. Figure 2 The flowchart illustrates the protection of the surge resistor R.

[0045] Figure 2 The flowchart relates to the operation of the surge protection unit 80 used to protect the surge protection resistor R. This flowchart illustrates the process (steps) that are repeated every sampling time ΔT (a few milliseconds). First, an overview of the flowchart is given. Here, for ease of explanation, the process along the straight line in the repeating loop flowchart is called the main process. Processes that branch off from the main process under certain decision conditions are called sub-processes.

[0046] First, in step 1, the surge protection unit 80 detects the DC output voltage VDCI of the converter unit 20 and the DC voltage VDC of the smoothing capacitor C. The detection method is arbitrary.

[0047] Next, in step 2, the surge protection unit 80 compares the DC output voltage VDCI of the converter unit 20 with the DC voltage VDC of the smoothing capacitor C. If the DC output voltage VDCI of the converter unit 20 is higher than the DC voltage VDC of the smoothing capacitor C ("Yes"), the surge protection unit 80 determines that a surge current has been generated to the smoothing capacitor C and proceeds to step 3. On the other hand, if the DC output voltage VDCI of the converter unit 20 is the same as or lower than the DC voltage VDC of the smoothing capacitor C ("No"), the surge protection unit 80 detours to the sub-process of step 11 and performs step 11, performing a subtraction process on the electrical charge W (alarm charge) used to determine whether an alarm should be issued. In step 11, the surge protection unit 80 subtracts a predetermined value from the electrical charge W.

[0048] In addition, unless explicitly stated or distinguished, the electrical quantities described in this specification generally refer to the electrical quantity generated in the surge protector R. However, this description should be understood in the context.

[0049] In step 2, if "Yes" is selected, the surge protector 80 then sets a timer and starts timing in step 3. In step 4, the surge protector 80 calculates a new charge W by adding the charge W for each sampling time to the charge W from the previous time, according to the mathematical formula described later. Furthermore, in step 5, the surge protector 80 also calculates a new short-term charge Ws for each sampled short-term charge Ws by adding that charge to the previous short-term charge Ws. Then, the surge protector 80 proceeds to step 6.

[0050] This also includes cases where step 11 is implemented in a sub-process after a detour. In step 6, the anti-surge resistor protection unit 80 determines whether the previously calculated power W exceeds a threshold. If it is determined that the power W exceeds the threshold, the anti-surge resistor protection unit 80 implements step 12 of the sub-process on the "yes" side and returns to the main process.

[0051] In step 12 of the subprocess, the surge protection unit 80 receives an electrical charge W exceeding the threshold, determines that the surge protection resistor R has an abnormal load, stops the inverter unit 70 and disconnects the electromagnetic contactor EC.

[0052] Therefore, the surge protection unit 80 calculates the alarm charge of the surge protection resistor R by accumulating the power when voltage is applied to the surge protection resistor R and subtracting a predetermined value from the accumulated power when no voltage is applied to the surge protection resistor R. When the alarm charge reaches a predetermined threshold, the inverter unit 70 is stopped and the electromagnetic contactor EC is disconnected.

[0053] That is, when the alarm power reaches the specified threshold, the surge protection unit 80 stops the drive of the inverter unit 70 and notifies the outside of the overload abnormality of the surge protection resistor R.

[0054] In step 6, the surge protection unit 80 determines whether the previously calculated electrical charge W exceeds a threshold. If it determines that the electrical charge W does not exceed the threshold, the surge protection unit 80 proceeds to step 7 according to the "No" side of the main flow.

[0055] In step 7, the surge protection unit 80 determines whether the time stamp set in step 3 remains unchanged. As described above, in step 2, when the DC output voltage VDCI of the converter unit 20 is higher than the DC voltage VDC of the smoothing capacitor C, the surge protection unit 80 determines that a surge current has been generated to the smoothing capacitor C, and sets the time stamp in step 3 through the main process on the "yes" side.

[0056] In step 7, if the time stamp remains unchanged, the surge protector 80 determines that the timing should continue and returns to the main process via the sub-process of step 13 (which is the "yes" side). On the other hand, if the time stamp is not set, the surge protector 80 directly transfers to the next step 8 via the main process (which is the "no" side).

[0057] In the sub-process of step 13, the anti-surge resistor protection unit 80 calculates the new cumulative time T by adding the sampling time ΔT to the previous cumulative time T and returns to the main process.

[0058] In step 8, the anti-surge resistor protection unit 80 determines whether the cumulative time T just before exceeded the specified value for measuring short-term electrical charge Ws (taking 3 seconds as an example).

[0059] In step 8, if the cumulative time T just before exceeded the specified value, the anti-surge resistor protection unit 80 determines that a short-term charge Ws has been obtained, and returns to the main process via the sub-process of step 14, which is the "yes" side.

[0060] In step 14, the surge protection unit 80 calculates the sum of the degradation amounts ΔD, which is the sum of the degradation amounts D and the degradation amount D from the previous time, based on the short-term charge Ws. Furthermore, the surge protection unit 80 calculates a new degradation amount D by adding the degradation amount D to the degradation amount sum ΔD.

[0061] In step 14, the surge protection unit 80 also clears the short-term charge Ws, time stamp, and cumulative time T, and returns to the main process.

[0062] In step 8, if the cumulative time T just before did not exceed the specified value for measuring short-term electrical charge Ws (3 seconds in this example), the surge protection resistor protection unit 80 directly proceeds to the main process on the "No" side.

[0063] In the main process, after step 8 or, depending on the situation, after step 14, as long as the operation of the motor control device 10 continues, the same process is repeated again starting from step 1.

[0064] The following section will explain the above process in detail, focusing on the control actions of the motor control device 10.

[0065] As described above, when driving the motor M, the electromagnetic contactor EC is turned on. As a result, the power supply voltage is fully rectified by the converter unit 20 to generate a DC voltage. This DC voltage will flow into the smoothing capacitor C. At this time, in step 1, the surge protection unit 80 measures the DC output voltage VDCI of the converter unit 20 and the DC voltage VDC of the smoothing capacitor C.

[0066] Next, in step 2, the anti-surge resistor protection unit 80 determines whether the DC output voltage VDCI of the converter unit 20 is greater than the DC voltage VDC of the smoothing capacitor C.

[0067] In step 2, if the DC output voltage VDCI of the converter unit 20 is greater than the DC voltage VDC of the smoothing capacitor C ("Yes"), the surge protection unit 80 determines that a surge current has been generated to the smoothing capacitor C, and initially sets a time stamp in step 3.

[0068] On the other hand, in step 2, if the DC output voltage VDCI of the converter unit 20 is the same as or smaller than the DC voltage VDC of the smoothing capacitor C ("No"), the surge protection unit 80 determines that no power based on surge current is generated in the surge protection resistor R and proceeds to step 11. Furthermore, the surge protection unit 80 performs a subtraction operation on the electrical quantity W, for example, based on the allowable repetition time (energy / allowable repetition time) corresponding to the specifications of the surge protection resistor R as shown in Table 1. If the electrical quantity W is 0 or less, the surge protection unit 80 stops the subtraction operation.

[0069] Furthermore, in steps 4 and 5, the surge protection unit 80, based on two voltages VDCI and VDC and the resistance value R of the surge protection resistor R, calculates the charge W generated in the surge protection resistor R at each sampling time ΔT and the short-term charge Ws over a specified time using the following mathematical formula. The contents of these two mathematical formulas are identical.

[0070] [Number 1]

[0071] The charge ΔW for each sampling is equal to (VDCI - VDC). 2 / R×ΔT

[0072] The short-term charge ΔWs for each sampling period is calculated as follows: ΔWs = (VDCI - VDC) 2 / R×ΔT

[0073] Here, the surge protection unit 80 adds the charge ΔW of the surge protection resistor R at each sampling time ΔT and the short-term charge ΔWs for a predetermined time to the charge W of the surge protection resistor R and the short-term charge Ws for the predetermined time at each sampling time. Thus, the surge protection unit 80 sets a new charge W of the surge protection resistor R and a new short-term charge Ws for the predetermined time.

[0074] Therefore, the electrical charge generated in the surge protector R up to this point can be calculated using the following mathematical formula. Here, the specified time is 3 seconds.

[0075] [Number 2]

[0076] Electric charge W = ∫(VDCI - VDC) 2 / Rdt

[0077] Short-term battery life

[0078] (where t0 = 0, t n =3)

[0079] In step 6, if the power exceeds the threshold ("Yes"), the anti-surge resistor protection unit 80 determines in step 12 that an overload abnormality of the anti-surge resistor R has been detected, stops the drive of the inverter unit 70, and disconnects the electromagnetic contactor EC to cut off the three-phase AC power supply S.

[0080] The threshold for detecting overload anomalies in the surge protector R used in step 6 is set to a threshold determined based on the relatively high amount of charge W among the charge quantities of the surge protector R for each specified durability cycle specified in the motor control device 10. For example, in the surge protector R specifications shown in Table 1, if the expected durability cycle of the surge protector R to meet the product durability cycle is 100,000 cycles, the threshold for the charge quantity W used for overload protection is typically set to 1400 J to meet the product durability cycle. On the other hand, in this embodiment, the threshold for the charge quantity W used for overload protection is set, for example, to a threshold where an anomaly is detected in the charge quantity W applied to the surge protector R when the smoothing capacitor C is charged and discharged three times in a short period of time. Therefore, even if a momentary power outage occurs when the power is turned on, and the smoothing capacitor C is charged and discharged twice in a short period of time, it will not be determined that an overload anomaly has occurred in the surge protector R.

[0081] Furthermore, even when the motor control device 10 has a multi-axis structure and the number of inverter units 70 is large, the threshold value for the electrical quantity W used for overload protection is set to a value at which no abnormality is detected during a single charge and discharge cycle. For example, for resistors with the specifications in Table 1, the threshold value for the electrical quantity W used for overload protection is set to a high value such as 2220J. Therefore, the number of durability cycles calculated based on this threshold, i.e., the threshold value for the electrical quantity W used for overload abnormality detection of the surge protector R, is less than the expected number of durability cycles for the surge protector R.

[0082] Next, in step 7, the surge protection resistor 80 determines whether to continue timing based on whether a time stamp has been set. If a time stamp has been set ("Yes"), the surge protection resistor 80 determines to continue timing, and in step 13 of the subprocess, it calculates a new cumulative time T by adding the sampling time ΔT to the previous cumulative time T.

[0083] Furthermore, in step 8, the surge protection resistor protection unit 80 determines whether the accumulated time T exceeds a predetermined value. If the accumulated time exceeds the predetermined value ("Yes"), the surge protection resistor protection unit 80 executes the next process in step 14 of the sub-process. The predetermined value will be explained later.

[0084] The surge protection unit 80 first calculates the cumulative degradation value ΔD of the surge protection resistor R based on the value of the short-term charge Ws at that point in time. The short-term charge Ws is the charge on the surge protection resistor R from the start of power application to the surge protection resistor R until a certain period of time has elapsed. The certain period of time is the short time required to calculate the cumulative degradation value ΔD by accumulating the charge intermittently applied to the surge protection resistor R during interruptions such as the recovery from a momentary power outage of the three-phase AC power supply S (as described above, it is set to 3 seconds here as an example). Furthermore, this short period of time is set to a predetermined value. If the value of the short-term charge Ws exceeds the expected number of durability cycles of the surge protection resistor R, the surge protection unit 80 calculates the cumulative degradation value ΔD using the following formula.

[0085] [Number 3]

[0086] Durability cycles under short-term charge Ws = K1 × short-term charge Ws

[0087] The sum of degradation ΔD = K2 / number of durability cycles under short-term charge Ws × 100

[0088] Here, K1 is a coefficient corresponding to the short-term charge, determining the relationship between the short-term charge and the number of durability cycles under the short-term charge, and is determined by the specifications of the surge protector R. Furthermore, K2 is a coefficient corresponding to the short-term charge, determining the relationship between the number of durability cycles under the short-term charge and the sum of degradation values ​​ΔD. For example, if the number of durability cycles under the short-term charge is one, coefficient K2 is determined such that the sum of degradation values ​​ΔD is 100%. Similarly, if the number of durability cycles under the short-term charge is two, coefficient K2 is determined such that the sum of degradation values ​​ΔD is 50%. Likewise, if the number of durability cycles under the short-term charge is N, coefficient K2 is determined such that the sum of degradation values ​​ΔD is 1 / N × 100%.

[0089] Therefore, coefficients K1 and K2 are the coefficients corresponding to the short-term energy Ws. A table corresponding to the short-term energy Ws is prepared in advance, and the sum of the degradation amounts ΔD is calculated based on this table. Figure 3 and Figure 4 This illustrates an example of a graph (table) created using this approach. Figure 3 The graph shown illustrates an example of the relationship between short-term charge Ws and the number of durability cycles under that short-term charge. Figure 4 This example illustrates the relationship between short-term energy consumption Ws and the sum of degradation ΔD.

[0090] Furthermore, the surge protector 80 calculates the degradation amount D at this point in time by adding the degradation amount summed to ΔD and then adding the degradation amount D calculated from the previous degradation amount summed to ΔD. Additionally, the surge protector 80 clears the short-term charge Ws, the time stamp, and the accumulated time T. The surge protector 80 also displays the degradation amount D on a monitor. The monitor can be of any type. Any monitor can be used as long as it can notify information to the outside in a manner recognizable to the operator. Furthermore, the monitor can be integrated with the surge protector 80 or be separate from it. The method of notification by the monitor can be any method, such as using images, sound, or light.

[0091] Furthermore, in step 8, if the cumulative time T does not exceed the specified value, the anti-surge resistor protection unit 80 returns to the main process and then repeats the same process that started from step 1.

[0092] In step 14 above, the degradation level D is displayed on the monitor. Therefore, if the degradation level D displayed on the monitor is close to 100%, maintenance personnel will perform maintenance work to replace the surge protector R or the motor control device 10. When the degradation level D is 0%, the surge protector R or the motor control device 10 can be used up to the expected number of service life cycles.

[0093] The above describes the operation of the control device for the motor M in this method. Alternatively, the DC output voltage VDCI of the converter unit 20 can be directly measured. Alternatively, if a circuit capable of detecting the voltage after full-wave rectification of the power supply voltage is provided, the DC output voltage VDCI can be calculated by detecting a voltage equivalent to (approximate to) the DC output voltage VDCI of the converter unit 20 using this circuit. Alternatively, the DC output voltage VDCI can be calculated by detecting the current flowing through the surge protector R, calculating the charge on the surge protector R, and then determining the DC output voltage VDCI based on the calculation result.

[0094] That is, the power of the surge current prevention circuit section 30’s surge resistor R can be calculated based on the voltage or current that can at least be approximated.

[0095] Alternatively, the capacitance C of the smoothing capacitor C and the DC voltage VDC of the smoothing capacitor C can be used to calculate the charge on the surge current prevention resistor R. That is, the charge on the surge current prevention resistor R of the surge current prevention circuit section 30 can also be calculated based on the DC voltage VDC of the smoothing capacitor C, the DC output voltage VDCI of the converter section 20, and the resistance value of the surge current prevention resistor R.

[0096] Furthermore, the charge W and short-term charge Ws of the surge protector R can be calculated only when the surge protector MS is off. Alternatively, the charge W and short-term charge Ws of the surge protector R can be calculated even when the surge protector MS is on. By calculating the charge W and short-term charge Ws of the surge protector R only when the surge protector MS is off, the following situation can be suppressed: due to the offset error of the detection section detecting VDCI and VDC, the overload abnormality or deterioration amount D of the surge protector R can be falsely detected during the operation of the motor M.

[0097] By calculating the charge W and short-term charge Ws of the surge protector R even when the surge protector MS is on, protection against the surge protector R can be provided in case the surge protector MS fails and disconnects during operation of the motor M. In this case, to suppress the influence of the offset error of the detection section detecting VDCI and VDC, it is preferable to calculate the charge W and short-term charge Ws of the surge protector R when the difference between VDCI and VDC is above a specified voltage. This suppresses the influence of the offset error.

[0098] The specified voltage is set to a small value that will not falsely detect the charge W of the anti-surge resistor R and the short-term charge Ws during the operation of the motor M with the anti-surge MS conducting.

[0099] Furthermore, the converter section 20 can also be a converter section 20 capable of power regeneration. In this case, even when the surge protection MS is on, the charge W and short-term charge Ws of the surge protection resistor R can be measured. That is, if the surge protection MS fails and disconnects during the regenerative operation of the motor M, the current regenerated from the smoothing capacitor C to the three-phase AC power supply S side through the converter section 20 flows through the surge protection resistor R. In the above structure, the surge protection resistor R can also be protected against this current.

[0100] In addition, the degradation amount D can also be calculated using a mathematical formula that approximates the value, without using a table.

[0101] Therefore, in addition to protecting the anti-surge resistor R during the initial charging before the start of operation of the motor M, this embodiment can also protect the anti-surge resistor when a relatively long momentary power outage occurs during the operation of the motor M and the current flows through the anti-surge resistor R when the power supply is restored, and protect the anti-surge resistor R when the anti-surge MS fails and disconnects.

[0102] Figures 5A to 5CThis illustrates examples of overload anomaly detection and degradation calculation during normal power supply and momentary power outages. The horizontal axis, starting from the leftmost point and moving to the right, represents the elapsed time. From top to bottom, it sequentially shows the on / off state of the three-phase AC power supply S, the on / off state of the electromagnetic contactor EC, VDC, the driving state of the motor M, the charge W of the surge protector R, alarm detection, short-term charge Ws, and the time variation of the degradation sum ΔD.

[0103] Figure 5A This describes the operation during normal power-on without a momentary power outage. If the electromagnetic contactor EC is initially turned on, VDC rises, and after a period of time, the motor M is able to operate. Since the charge W of the surge protector R does not reach the level required to detect an abnormality, it is not treated as an overload anomaly for the surge protector R. Furthermore, since the short-term charge Ws does not exceed the expected lifespan of the surge protector R, the degradation D does not increase. Therefore, under normal power-on conditions without a momentary power outage, the surge protector R can be used up to its expected lifespan.

[0104] Figure 5B This illustrates an example of a momentary power outage occurring when power is switched on. As shown in the diagram, the electromagnetic contactor EC is turned on, and after VDC rises, a momentary power outage occurs. If a momentary power outage occurs, the accumulated power is discharged from VDC during the outage. Afterward, the three-phase AC power supply S is restored, and VDC rises. Regarding the short-term charge Ws at this time, power is continuously generated in the surge protector R during this short period. However, since the total charge does not reach the anomaly detection threshold, no alarm is detected, and the motor M is temporarily able to operate. On the other hand, the short-term charge Ws exceeds the expected number of cycles of the surge protector R. Therefore, due to the sum of the degradation values ​​ΔD calculated as described above, the previous degradation D increases accordingly, and the degradation D worsens.

[0105] Figure 5C This illustrates an example of two momentary power outages occurring during power-on. As shown in the figure, after the electromagnetic contactor EC is turned on and VDC rises, two momentary power outages occur consecutively. If a momentary power outage occurs, the charge accumulated in the smoothing capacitor is discharged during the outage, and VDC decreases. Subsequently, the three-phase AC power supply S is restored, VDC rises again, and charging of VDC begins again. However, if a second momentary power outage occurs, the accumulated charge is discharged again during the outage, and VDC decreases. Then, the three-phase AC power supply S is restored, and VDC gradually rises to a state sufficient for the inverter section 70 to operate.

[0106] At this point, the charge W in the surge protector R reaches the threshold used to detect overload anomalies. Therefore, an alarm is detected, and the electromagnetic contactor EC disconnects. Furthermore, regarding the short-term charge Ws at this time, during this short period, power is generated three times consecutively in the surge protector R, and the sum of the short-term charge Ws reaches the charge level required for a lower durability cycle. Therefore, compared to the example of a momentary power outage occurring when power is switched on, the sum of the degradation values ​​ΔD calculated above becomes larger. The previous degradation D increases accordingly, and the degradation D further deteriorates.

[0107] Therefore, in this method, by detecting overload anomalies in the surge protector R, the open circuit of the surge protector R caused by excessive electrical charge is suppressed. Regarding the point where the durability cycle of the surge protector R falls below the expected durability cycle, the sum of the degradation amount corresponding to the short-term electrical charge value (degradation sum) ΔD is calculated, the degradation amount D is calculated, and the degradation amount D is displayed on the monitor. Thus, after the degradation amount D approaches 100%, it is possible to identify a situation where maintenance work should be performed to replace the surge protector R or the motor control device 10. Therefore, it is possible to suppress subsequent open circuits of the surge protector R caused by new degradation.

[0108] The foregoing description details the embodiments of the present invention. In the above embodiments, the illustrated structures, etc., are not particularly limited. Furthermore, the illustrated or described embodiments can be appropriately modified without impairing the technical effects of the present invention. Moreover, the above embodiments can be appropriately modified for implementation as long as they do not depart from the scope of the present invention.

[0109] Furthermore, one embodiment of the electric motor control device of the present invention may be a first electric motor control device. The first electric motor control device comprises, in this order, an input switch unit capable of connecting to a power source, a converter unit that outputs power from the power source as DC power, a capacitor unit that holds the DC power, an inverter unit that converts the DC power to AC power, and a motor driven by the inverter unit. The first electric motor control device includes: an inrush current prevention circuit unit disposed between the converter unit and the capacitor unit, having an inrush current prevention resistor and an inrush current prevention switch for suppressing inrush current during charging of the capacitor unit; and an inrush current prevention resistor protection unit that protects the inrush current prevention resistor. The electric motor control device is characterized in that the inrush current prevention resistor protection unit calculates the power passing through the inrush current prevention resistor, calculates a short-term power consumption over a predetermined time period, and, based on the short-term power consumption over the predetermined time period, generates information on the degradation amount of the inrush current prevention resistor and notifies the externally of the degradation amount.

[0110] The detailed description has been given for illustrative and explanatory purposes. Many variations and modifications are possible in accordance with the teachings above. The detailed description is not without omissions or intended to limit the subject matter described herein. Although the subject matter has been described in words with particular structural features and / or methodological processes, it should be understood that the subject matter defined in the claims is not necessarily limited to the specific features or processes described. Rather, the specific features and processes described are illustrated as examples of implementing the claims.

Claims

1. A motor control device, characterized in that, include: The converter section is connected to an input switch section that can be connected to a power source, and outputs power from the power source as DC power. The capacitor section maintains the DC power; and The inverter section converts the DC power into AC power and drives the motor. The input switch section, the converter section, the capacitor section, and the inverter section are connected in sequence. The motor control device further includes: An inrush current prevention circuit section is provided between the converter section and the capacitor section, and includes an inrush current prevention resistor and an inrush current prevention switch to suppress inrush current during charging of the capacitor section; and The surge protector section protects the surge protector. The surge protection unit calculates the power passing through the surge resistor, calculates the short-term power during a specified time period, and generates information on the degradation level of the surge resistor based on the short-term power during the specified time period and notifies the external system of the degradation level.

2. The motor control device according to claim 1, characterized in that, The surge protection unit calculates the alarm charge of the surge protector by accumulating power when voltage is applied to the surge protector and subtracting a predetermined value from the accumulated power when no voltage is applied to the surge protector. When the alarm charge reaches a predetermined threshold, the inverter unit is stopped from driving and the input switch unit is disconnected.

3. The motor control device according to claim 1 or 2, characterized in that, The surge protection unit calculates the number of durability cycles corresponding to the short-term power consumption based on the specifications of the surge protection resistor. It calculates the sum of the degradation values ​​by calculating the reciprocal of the number of durability cycles corresponding to the short-term power consumption, and then calculates the degradation amount by adding this degradation value to the previous degradation amount.

4. The motor control device according to claim 1 or 2, characterized in that, The surge protection unit calculates the short-term charge of the surge protector by accumulating the charge from the start of voltage application to the surge protector until a certain period of time has elapsed.

5. The motor control device according to claim 2, characterized in that, When the alarm charge reaches the specified threshold, the surge protection unit stops the inverter and notifies the outside of the overload abnormality of the surge protection resistor.

6. The motor control device according to claim 1 or 2, characterized in that, The power is calculated through the surge current prevention circuit section's surge resistor based on the voltage or current that can at least be approximated by the power.

7. The motor control device according to claim 1 or 2, characterized in that, Based on the voltage of the capacitor section, the output voltage of the converter section, and the resistance value of the surge current prevention resistor, the power of the surge current prevention circuit section through the surge current prevention resistor is calculated.

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