Motor drive device for calculating insulation resistance value of motor

Abstract

A motor drive device (1) includes: a converter section (11) that converts input AC power into DC power to output to a DC link; a DC link capacitor (4); voltage dividing resistors (13-1, 13-2) that are connected in series to each other between a positive potential line and a negative potential line of the DC link; a measurement resistor (14) that is connected between a connection point of the voltage dividing resistors (13-1, 13-2) and the positive potential line or the negative potential line of the DC link; a resistor voltage measurement section (15) that measures a resistor voltage of the measurement resistor (14); a DC component extraction section (16) that extracts a DC component of the resistor voltage; an AC component extraction section (17) that extracts an AC component of the resistor voltage; a DC link potential measurement section (18) that measures the positive potential and the negative potential of the DC link; and an insulation resistance value calculation section (19) that calculates an insulation resistance value of a motor (3) based on the DC component and the AC component of the resistor voltage and the positive potential and the negative potential of the DC link.

Description

TECHNICAL FIELD

[0001] The present application relates to a motor drive device that calculates an insulation resistance value of a motor. BACKGROUND

[0002] In a motor drive device that controls driving of a motor in a machine tool, a forging press, an injection molding machine, an industrial machine, or various robots, alternating-current power input from an alternating-current power source is converted into direct-current power by a converter section (rectification circuit) to be output to a DC link, and the direct-current voltage in the DC link is converted into alternating-current power by an inverter section to supply the alternating-current power as driving power of the motor. The "DC link" refers to a circuit portion that electrically connects the direct-current output side of the converter section and the direct-current input side of the inverter section, and is sometimes also referred to as a "DC link section", a "direct-current link", a "direct-current link section", or a "direct-current intermediate circuit", and the like.

[0003] For some reason, a motor failure can sometimes occur due to deterioration of insulation of the motor. The deterioration of the insulation of the motor is detected by measuring the resistance value between the winding of the motor and the ground, that is, the insulation resistance value.

[0004] For example, a motor drive device is known that is characterized by having: a rectification circuit that rectifies an alternating-current voltage supplied from an alternating-current power source via a first switch into a direct-current voltage; a power supply section that smoothes the direct-current voltage rectified by the rectification circuit using a capacitor; an inverter section that drives a motor by converting the direct-current voltage smoothed by the power supply section into an alternating-current voltage through switching operation of a semiconductor switching element; a current detection section that measures a current value flowing through a resistor having one end connected to a coil of the motor and the other end connected to one terminal of the capacitor; a voltage detection section that measures a voltage value across the capacitor; a second switch that grounds the other terminal of the capacitor; and an insulation resistance detection section that stops operation of the motor, detects the resistance between the coil of the motor and the ground, that is, the insulation resistance value of the motor, using two sets of the current value and the voltage value measured in two states in which the first switch is turned off and the second switch is turned off and in which the first switch is turned on and the second switch is turned on (for example, refer to Patent Literature 1).

[0005] For example, an insulation deterioration detection device of an electric motor that detects occurrence of insulation deterioration of a field winding in an alternating-current electric motor in operation is known, and is characterized by including: a plurality of detection elements that individually detect an electromagnetic wave at the time of occurrence of partial discharge in the field winding of each phase of the alternating-current electric motor; a ground line that grounds output signals from the plurality of detection elements together; a detection unit that extracts a partial discharge signal from the ground line; a determination unit that determines whether the partial discharge is above a permissible level based on an output signal of the detection unit; and an alarm unit that outputs an alarm when the determination unit determines the partial discharge to be above the permissible level (for example, refer to Patent Literature 2).

[0006] Prior Art Documents

[0007] Patent Literature

[0008] Patent Literature 1: Japanese Patent Application Publication No. 2015-129704

[0009] Patent Literature 2: Japanese Patent Application Publication No. 2002-311080 SUMMARY

[0010] Problems to be Solved by the Invention

[0011] In the past, when measuring the insulation resistance value of an electric motor, the electric motor driving device that drives the electric motor is cut off from the alternating-current power source to perform the measurement. However, every time the insulation resistance value of the electric motor is measured, the cut-off work and the connection work of the electric motor driving device and the alternating-current power source take labor and time, and the efficiency is poor. In addition, it is also considered to provide a circuit breaker between the electric motor driving device and the alternating-current power source, but there is a disadvantage of an increase in cost. Therefore, a technology that can measure the insulation resistance value of an electric motor at low cost without disconnecting the electric motor driving device from the alternating-current power source is desired.

[0012] Means for Solving the Problems

[0013] According to one embodiment of the present disclosure, a motor drive device includes: a converter section that converts alternating-current power input from an alternating-current power source into direct-current power to output to a DC link; a DC link capacitor provided in the DC link; an inverter section that converts the direct-current power in the DC link into alternating-current power for driving a motor and outputs the alternating-current power; a voltage dividing resistor that is two voltage dividing resistors provided in series connection between a positive potential line and a negative potential line that constitute the DC link, connects connection points of the voltage dividing resistors to a winding of the motor; a measurement resistor connected between the connection points of the voltage dividing resistors and the positive potential line or the negative potential line of the DC link; a resistor voltage measurement section that measures a resistor voltage that is a potential difference across the measurement resistor; a DC component extraction section that extracts a DC component from the resistor voltage measured by the resistor voltage measurement section; an AC component extraction section that extracts an AC component from the resistor voltage measured by the resistor voltage measurement section; a DC link potential measurement section that measures a positive potential in the positive potential line and a negative potential in the negative potential line of the DC link; and an insulation resistance value calculation section that calculates an insulation resistance value of the motor based on the DC component extracted by the DC component extraction section, the AC component extracted by the AC component extraction section, and the positive potential and the negative potential measured by the DC link potential measurement section.

[0014] Effects of Invention

[0015] According to one embodiment of the present disclosure, it is possible to measure an insulation resistance value of a motor at low cost without disconnecting a motor drive device from an alternating-current power source. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A motor drive device (first embodiment) representing one embodiment of the present disclosure.

[0017] Figure 2 A variation of the motor drive device (first embodiment) representing one embodiment of the present disclosure.

[0018] Figure 3 Equivalent circuit (1) for deriving Formula 1 in the calculation processing of the insulation resistance value calculation section of the first embodiment.

[0019] Figure 4 Equivalent circuit (2) for deriving Formula 1 in the calculation processing of the insulation resistance value calculation section of the first embodiment.

[0020] Figure 5 Equivalent circuit (3) for deriving Formula 1 in the calculation processing of the insulation resistance value calculation section of the first embodiment.

[0021] Figure 6 Equivalent circuit (4) for deriving Formula 1 in the calculation processing of the insulation resistance value calculation section of the first embodiment.

[0022] Figure 7 Equivalent circuit (1-5) of Equation 1 used for deriving the calculation process of the insulation resistance value calculation section of the first method.

[0023] Figure 8 Equivalent circuit (1-6) of Equation 1 used for deriving the calculation process of the insulation resistance value calculation section of the first method.

[0024] Figure 9 Equivalent circuit (1-7) of Equation 1 used for deriving the calculation process of the insulation resistance value calculation section of the first method.

[0025] Figure 10 Equivalent circuit (1-8) of Equation 1 used for deriving the calculation process of the insulation resistance value calculation section of the first method.

[0026] Figure 11 Motor drive device (second method) of an embodiment of the present disclosure is shown.

[0027] Figure 12 Equivalent circuit (11-1) of Equation 11 used for deriving the calculation process of the insulation resistance value calculation section of the second method.

[0028] Figure 13 Equivalent circuit (11-2) of Equation 11 used for deriving the calculation process of the insulation resistance value calculation section of the second method.

[0029] Figure 14 Equivalent circuit (11-3) of Equation 11 used for deriving the calculation process of the insulation resistance value calculation section of the second method.

[0030] Figure 15 Equivalent circuit (11-4) of Equation 11 used for deriving the calculation process of the insulation resistance value calculation section of the second method.

[0031] Figure 16 Equivalent circuit (11-5) of Equation 11 used for deriving the calculation process of the insulation resistance value calculation section of the second method.

[0032] Figure 17 Equivalent circuit (11-6) of Equation 11 used for deriving the calculation process of the insulation resistance value calculation section of the second method.

[0033] Figure 18 Equivalent circuit (11-7) of Equation 11 used for deriving the calculation process of the insulation resistance value calculation section of the second method.

[0034] Figure 19 Flowchart showing the flow of operation of the motor drive device of an embodiment of the present disclosure.

[0035] Figure 20 The simulation results illustrate the positive and negative potentials of the DC link when an AC power supply is connected to a motor drive device according to an embodiment of this disclosure via a delta connection. Detailed Implementation

[0036] The following description, with reference to the accompanying drawings, describes a motor drive device for calculating the insulation resistance value of an electric motor. In each drawing, the same reference numerals are used to label the same parts. Furthermore, the scales of these drawings have been appropriately altered for ease of understanding. Also, the arrangement shown in the drawings is an example for implementation and is not limited to the illustrated arrangement.

[0037] Figure 1 This describes a motor drive device (first embodiment) according to one embodiment of the present disclosure. Details will be described later. One end of the measuring resistor 14 is connected to either the negative or positive potential line of the DC link. Connecting one end of the measuring resistor 14 to the negative potential line of the DC link is referred to as the first embodiment, and connecting one end of the measuring resistor 14 to the positive potential line of the DC link is referred to as the second embodiment. The first and second embodiments differ only in whether one end of the measuring resistor 14 is connected to the negative or positive potential line of the DC link.

[0038] As an example, this illustration shows a case where a motor drive device 1 connected to an AC power supply 2 controls a motor 3. In this embodiment, the type of motor 3 is not particularly limited; for example, it can be an induction motor or a synchronous motor. Furthermore, the number of phases of the AC power supply 2 and the motor 3 is not particularly limited in this embodiment; for example, it can be three-phase or single-phase. In the illustrated example, both the AC power supply 2 and the motor 3 are three-phase. Examples of AC power supplies 2 include three-phase 400V AC power, three-phase 200V AC power, three-phase 600V AC power, and single-phase 100V AC power. Machinery equipped with the motor 3 includes, for example, machine tools, robots, forging machinery, injection molding machines, industrial machinery, various electrical products, trams, automobiles, and airplanes.

[0039] like Figure 1 As shown, an embodiment of the electric motor drive device 1 of this disclosure includes a converter unit 11, a DC link capacitor 4, an inverter unit 12, two voltage divider resistors 13-1 and 13-2, a measuring resistor 14, a resistance voltage measuring unit 15, a DC component extraction unit 16, an AC component extraction unit 17, a DC link potential measuring unit 18, and an insulation resistance value calculation unit 19.

[0040] The converter section 11 converts the alternating-current power input from the alternating-current power source 2 into direct-current power and outputs to the DC link as a direct-current output side. The converter section 11 is configured by a three-phase bridge circuit in a case where three-phase alternating-current power is supplied from the alternating-current power source 2, and is configured by a single-phase bridge circuit in a case where single-phase alternating-current power is supplied from the alternating-current power source 2. In the example illustrated, the alternating-current power source 2 is provided as a three-phase alternating-current power source, and thus the converter section 11 is configured by a three-phase bridge circuit. As an example of the converter section 11, there are a diode rectifier, a 120-degree conduction method rectifier, a PWM switching control method rectifier, and the like. For example, in a case where the converter section 11 is a 120-degree conduction method rectifier or a PWM switching control method rectifier, the bridge circuit is configured by a switching element and a diode connected in anti-parallel to the switching element, and the power conversion is performed by on-off control of each switching element in accordance with a drive command received from a higher-level control device (not illustrated). In this case, as an example of the switching element, there are an FET, an IGBT, a thyristor, a GTO (Gate Turn-OFF thyristor), a transistor, and the like, but other semiconductor elements can also be used.

[0041] The inverter section 12 converts the direct-current power in the DC link into alternating-current power for driving the motor 3 and outputs. The inverter section 12 is configured by a bridge circuit of a switching element and a diode connected in anti-parallel to the switching element. The inverter section 12 is configured by a three-phase bridge circuit in a case where the motor 3 is a three-phase alternating-current motor, and is configured by a single-phase bridge circuit in a case where the motor 3 is a single-phase alternating-current motor. In the example illustrated, the motor 3 is provided as a three-phase alternating-current motor, and thus the inverter section 12 is configured by a three-phase bridge circuit. The inverter section 12 controls the power conversion operation, for example, by a PWM switching control method. That is, the inverter section 12 receives a PWM switching command from a higher-level control device (not illustrated), converts the direct-current power in the DC link into alternating-current power for driving the motor 3 and outputs to the motor 3, and converts alternating-current power regenerated by the motor 3 into direct-current power and returns to the DC link side at the time of motor regeneration.

[0042] The inverter section 12 is controlled by the higher-level control device (not illustrated) in the same manner as a general motor drive device. That is, the higher-level control device generates a switching command for controlling the speed, torque, or position of the rotor of the motor 3 on the basis of the speed (speed feedback) of the motor 3, the current (current feedback) flowing through the winding of the motor 3, a predetermined torque command, an operation program of the motor 3, and the like. The power conversion operation of the inverter section 12 is controlled on the basis of the PWM switching command generated by the higher-level control device.

[0043] In a DC link connecting the DC output side of the converter section 11 and the DC input side of the inverter section 12, a DC link capacitor 4 is provided. The DC link capacitor 4 has a function of suppressing the amount of pulsation of the DC output of the converter section 11 and a function of accumulating DC power used for the inverter section 12 to generate AC power. As examples of the DC link capacitor 4, there are, for example, electrolytic capacitors, film capacitors, and the like.

[0044] Between the positive potential line and the negative potential line constituting the DC link, two voltage dividing resistors 13-1 and 13-2 connected in series with each other are provided. The voltage dividing resistors 13-1 and 13-2 divide the potential difference between the positive potential in the positive potential line and the negative potential in the negative potential line of the DC link, that is, the DC link voltage. The connection point of the voltage dividing resistors 13-1 and 13-2 is connected to the winding (input terminal) of the motor 3. In Figure 1 In the example shown, the voltage dividing resistors 13-1 and 13-2 are each constituted by each DC link resistor of two DC link resistors connected in series with each other between the positive potential line and the negative potential line of the DC link. The DC link resistors are constituted by ordinary resistors. It is preferable that the resistance value of the voltage dividing resistor 13-1 and the resistance value of the voltage dividing resistor 13-2 be substantially equal, and in Figure 1 In the example shown, the resistance value is set to R. However, the resistance value of the voltage dividing resistor 13-1 and the resistance value of the voltage dividing resistor 13-2 can have different values. Each resistance value R of the voltage dividing resistors 13-1 and 13-2 can be determined in advance or a value specified in a specification table related to the voltage dividing resistors 13-1 and 13-2 can be used.

[0045] A measurement resistor 14 is connected between the connection point of the voltage dividing resistors 13-1 and 13-2 and the positive potential line or the negative potential line of the DC link. In Figure 1 In the example shown, the measurement resistor 14 is connected between the connection point of the voltage dividing resistors 13-1 and 13-2 and the negative potential line of the DC link. The measurement resistor 14 is constituted by an ordinary resistor. The resistance value of the measurement resistor 14 is set to R in . The resistance value R in of the measurement resistor 14 can be determined in advance or a value specified in a specification table related to the measurement resistor 14 can be used.

[0046] The resistor voltage measurement section 15 measures the resistor voltage, which is the potential difference between both ends of the measurement resistor 14, in a state in which the power conversion operation of the inverter section 12 is stopped, that is, in a state in which all the switching elements in the inverter section 12 are turned off. A signal related to the resistor voltage of the measurement resistor 14 measured by the resistor voltage measurement section 15 is transmitted to the DC component extraction section 16 and the AC component extraction section 17.

[0047] The DC component extraction section 16 extracts a DC component from the resistance voltage measured by the resistance voltage measurement section 15. The DC component extraction section 16 is configured by, for example, a low-pass filter that removes an AC component from a signal output from the resistance voltage measurement section 15 to output a DC component. A signal related to the DC component of the resistance voltage extracted by the DC component extraction section 16 is sent to the insulation resistance value calculation section 19.

[0048] The AC component extraction section 17 extracts an AC component from the resistance voltage measured by the resistance voltage measurement section 15. The AC component extraction section 17 is configured by, for example, a high-pass filter that removes a DC component from a signal output from the resistance voltage measurement section 15 to output an AC component. A signal related to the AC component of the resistance voltage extracted by the AC component extraction section 17 is sent to the insulation resistance value calculation section 19.

[0049] The DC link potential measurement section 18 measures a positive potential in the positive potential line and a negative potential in the negative potential line of the DC link in a state in which the power conversion operation of the inverter section 12 is stopped (i.e., a state in which all the switching elements in the inverter section 12 are turned off). A signal related to the positive potential and the negative potential of the DC link measured by the DC link potential measurement section 18 is sent to the insulation resistance value calculation section 19.

[0050] The insulation resistance value calculation section 19 calculates the resistance value of the insulation resistance 20 between the winding of the motor 3 and the ground, i.e., the insulation resistance value R, on the basis of the DC component of the resistance voltage extracted by the DC component extraction section 16, the AC component of the resistance voltage extracted by the AC component extraction section 17, and the positive potential and the negative potential of the DC link measured by the DC link potential measurement section 18. m The details of the calculation processing performed by the insulation resistance value calculation section 19 will be described later.

[0051] In the embodiment described with reference to Figure 1 The division resistance 13-1 and the division resistance 13-2 are each configured by a respective one of two DC link resistors connected in series with each other between the positive potential line and the negative potential line of the DC link. As a modification example thereof, the off resistance of the switching elements in the bridge circuit in the inverter section 12 can be used as the division resistances 13-1 and 13-2. Figure 2A modification of the motor drive device (first mode) representing an embodiment of the present disclosure. If the switching elements respectively provided in the upper arm and the lower arm in the same phase constituting the bridge circuit within the inverter section 12 are turned off, an off resistance having a predetermined resistance value is generated. The off resistance related to the switching elements of the upper arm and the lower arm in the same phase has a function of dividing the DC link voltage, and thus the off resistance of the switching elements of the upper arm and the lower arm in the same phase can be used as the dividing resistors 13-1 and 13-2. In this modification, the resistance value of the off resistance of the switching elements is set to R. The resistance value R of the off resistance of the switching elements can be calculated based on the measurement result of the voltage at the time of turning off the switching elements.

[0052] Next, the calculation processing of the insulation resistance value calculation section 19 is described for the first mode in which one end of the measurement resistance 14 is connected to the negative potential line of the DC link and the second mode in which one end of the measurement resistance 14 is connected to the positive potential line of the DC link.

[0053] First, the calculation processing of the insulation resistance value calculation section 19 of the first mode in which one end of the measurement resistance 14 is connected to the negative potential line of the DC link is described.

[0054] As described above, Figure 1 and Figure 2 The first mode in which one end of the measurement resistance 14 is connected to the negative potential line of the DC link, that is, the measurement resistance 14 is connected between the connection point of the dividing resistor 13-1 and the dividing resistor 13-2 and the negative potential line of the DC link is represented.

[0055] In the first mode represented in FIG. 8, Figure 1 and Figure 2 In the first mode represented in FIG. 8, the insulation resistance value calculation section 19 calculates the insulation resistance value R of the motor 3 according to Formula 1 m In Formula 1, the resistance value of the measurement resistance 14 is set to R in The value of the positive potential of the DC link at the time when the power conversion operation of the inverter section 12 is stopped, which is measured by the DC link potential measurement section 18, is set to V p The value of the negative potential of the DC link at the time when the power conversion operation of the inverter section 12 is stopped, which is measured by the DC link potential measurement section 18, is set to V n The value of the DC component of the resistance voltage at the time when the power conversion operation of the inverter section 12 is stopped, which is extracted by the DC component extraction section 16 (low-pass filter), is set to V inL The value of the AC component of the resistance voltage at the time when the power conversion operation of the inverter section 12 is stopped, which is extracted by the AC component extraction section 17 (high-pass filter), is set to V inH The value V com is set to (V p + V n) / 2, the value V dif is set to (V p -V n ) / 2.

[0056] [Formula 1]

[0057]

[0058] Here, the derivation process of Formula 1 used in the calculation processing of the insulation resistance value calculation section 19 in the first mode in which one end of the measurement resistor 14 is connected to the negative potential line of the DC link will be described. Figures 3-10 An equivalent circuit for deriving Formula 1 used in the calculation processing of the insulation resistance value calculation section in the first mode is shown in FIG. 9.

[0059] In the calculation of the insulation resistance value R m performed by the insulation resistance value calculation section 19, data measured by the resistor voltage measurement section 15 and the DC link potential measurement section 18 in a state in which the power conversion operation of the inverter section 12 is stopped is used. In the state in which the power conversion operation of the inverter section 12 is stopped, circuits related to the inverter section 12 do not appear in Figures 3-10 .

[0060] In Figure 3 , the positive potential V p in the positive potential line of the DC link shown in Figure 1 and Figure 2 is represented by an equivalent power source 31. Similarly, in Figure 3 , the negative potential V n in the negative potential line of the DC link shown in Figure 1 and Figure 2 is represented by an equivalent power source 32. At this time, as shown in Figure 3 , the equivalent power sources 31 and 32 are connected to the voltage dividing resistors 13-1 and 13-2 shown in Figure 1 and Figure 2 , the measurement resistor 14, and the insulation resistance 20 of the motor 3. The resistance values of the voltage dividing resistors 13-1 and 13-2 are set to R in , the resistance value of the measurement resistor 14 is set to R m , and the resistance value of the insulation resistance 20 of the motor 3 is set to R in . The value of the resistor voltage of the measurement resistor 14 measured by the resistor voltage measurement section 15 is set to V n .

[0061] In the equivalent circuit shown in Figure 3 , the equivalent power source 32 is connected to one end of the voltage dividing resistor 13-2 and one end of the measurement resistor 14, and thus, as shown in Figure 4 , the equivalent power source 32 can be decomposed into equivalent power sources 33 and 34 having the same voltage value V nThe two equivalent power sources are 32 and 33. That is, as shown... Figure 4 As shown, an equivalent power supply 32 is connected to one end of the voltage divider resistor 13-2, and an equivalent power supply 33 is connected to one end of the measuring resistor 14.

[0062] exist Figure 4 In the equivalent circuit shown, if Thevenin's theorem is applied to circuit part T1, then we can obtain... Figure 5 The equivalent circuit is shown. Figure 5 In the equation, the voltage value V1 of the equivalent power supply 34 is represented by Equation 2, and the resistance value of the equivalent resistor 21 is R / 2.

[0063] [Formula 2]

[0064]

[0065] exist Figure 5 In the equivalent circuit shown, if Thevenin's theorem is applied to circuit part T2, then we can obtain... Figure 6 The equivalent circuit shown is illustrated. Figure 6 In the equation, the voltage value V2 of the equivalent power supply 35 is represented by Equation 3, and the resistance value R1 of the equivalent resistance 22 is represented by Equation 4.

[0066] [Formula 3]

[0067]

[0068] [Formula 4]

[0069]

[0070] exist Figure 6 In the equivalent circuit shown, equivalent power supply 33 and equivalent power supply 35 are connected in series via equivalent resistor 22 and measuring resistor 14. Therefore, if equivalent power supply 33 and equivalent power supply 35 are combined into one, we obtain... Figure 7 The equivalent power source 36 is shown. In Figure 7 In the equation, the voltage value V3 of the equivalent power source 36 is represented by Equation 5.

[0071] [Formula 5]

[0072]

[0073] exist Figure 7 In the equivalent circuit shown, when the voltage value V3 of the equivalent power supply 36 is divided into differential and in-phase components, the following is obtained: Figure 8 The equivalent power supplies 37 and 38 are shown. In Figure 8 In the equation, the voltage value V4 of the equivalent power source 37 is the differential component, represented by Equation 6. The voltage value V5 of the equivalent power source 38 is the in-phase component, represented by Equation 7.

[0074] [Formula 6]

[0075]

[0076] [Formula 7]

[0077]

[0078] Figure 8 The equivalent circuit shown can be divided into Figure 9 the equivalent circuit of the direct current component shown in Figure 10 the equivalent circuit of the alternating current component shown in.

[0079] As Figure 9 shown in the equivalent circuit of the direct current component, the equivalent resistor 22 and the measurement resistor 14 are connected to the equivalent power source 37 having the differential component V4. If the voltage component V inL applied to the measurement resistor 14 is found using Ohm's law, it is expressed as Formula 8. In Formula 8, the signal component not containing the direct current component, i.e., (V p + V n ) / 2, is replaced by V com , and the signal component containing the direct current component, (V p - V n ) / 2, is replaced by V dif . The voltage component V inL corresponds to the direct current component obtained by removing the alternating current component from the resistance voltage of the measurement resistor 14 measured by the resistance voltage measurement section 15 through the direct current component extraction section 16 (low pass filter).

[0080] [Formula 8]

[0081]

[0082] As Figure 10 shown in the equivalent circuit of the alternating current component, the equivalent resistor 22 and the measurement resistor 14 are connected to the equivalent power source 38 having the in-phase component V5. If the voltage component V inH applied to the measurement resistor 14 is found using Ohm's law, it is expressed as Formula 9. In Formula 9, the signal component not containing the direct current component, i.e., (V p + V n ) / 2, is replaced by V com , and the signal component containing the direct current component, (V p - V n ) / 2, is replaced by V dif . The voltage component V inH corresponds to the alternating current component obtained by removing the direct current component from the resistance voltage of the measurement resistor 14 measured by the resistance voltage measurement section 15 through the alternating current component extraction section 17 (high pass filter).

[0083] [Equation 9]

[0084]

[0085] For the insulation resistance value R m By solving the simultaneous equations of Equation 8 and Equation 9, Equation 1 for calculating the insulation resistance value R m is obtained. In the first mode in which one end of the measuring resistor 14 is connected to the negative potential line of the DC link, the insulation resistance value calculating section 19 calculates the insulation resistance value R m of the motor 3 according to Equation 1. In Equation 1, the value V com is represented by (V p + V n ) / 2, and the value V dif is represented by (V p - V n ) / 2. V p is the positive potential in the positive potential line of the DC link measured by the DC link potential measuring section 18 at the time when the power conversion operation of the inverter section 12 is stopped. V n is the negative potential in the negative potential line of the DC link measured by the DC link potential measuring section 18 at the time when the power conversion operation of the inverter section 12 is stopped. The DC component V inL is obtained by removing the AC component from the resistance voltage of the measuring resistor 14 measured by the resistance voltage measuring section 15 at the time when the power conversion operation of the inverter section 12 is stopped, by the DC component extracting section 16 (low-pass filter). The AC component V inH is obtained by removing the DC component from the resistance voltage of the measuring resistor 14 measured by the resistance voltage measuring section 15 at the time when the power conversion operation of the inverter section 12 is stopped, by the AC component extracting section 17 (high-pass filter). As for the resistance value R in of the measuring resistor 14, it is sufficient to use a value specified in a specification table or to measure it in advance. In addition, each resistance value R of the voltage dividing resistors 13-1 and 13-2 can be calculated by solving the simultaneous equations of Equation 8 and Equation 9. That is, "calculating the insulation resistance value R m of the motor 3 according to Equation 1" means "calculating the insulation resistance value R inL of the motor 3 based on the DC component V inH of the resistance voltage extracted by the DC component extracting section 16, the AC component V p of the resistance voltage extracted by the AC component extracting section 17, and the positive potential V n and the negative potential V m of the DC link measured by the DC link potential measuring section 18".

[0086] Further, in the first mode, as for the value V com and the AC component VinH and the value V dif and the direct current component V inL , the alternating current component V inH extracted by the alternating current component extraction section 17 is rectified and an absolute value is taken, and based on the value, the insulation resistance value R m of the motor 3 is calculated in accordance with Equation 10. Alternatively, for example, the alternating current component V inH extracted by the alternating current component extraction section 17 is rectified and an absolute value is taken, and the direct current component V inL extracted by the direct current component extraction section 16 is rectified and an absolute value is taken, and based on these values, the insulation resistance value R m of the motor 3 is calculated in accordance with Equation 10. Further, since the absolute values of the alternating current component V inH of Equation 9 and the direct current component V inL of Equation 8 are taken, Equation 10 differs in part of the symbols from Equation 1.

[0087] [Equation 10]

[0088]

[0089] Next, the calculation processing of the insulation resistance value calculation section 19 of the second mode in which one end of the measurement resistance 14 is connected to the positive potential line of the DC link will be described.

[0090] Figure 11 A motor drive device (second mode) according to an embodiment of the present disclosure is shown. In the second mode, the measurement resistance 14 is connected between the connection point of the voltage dividing resistors 13-1 and 13-2 and the positive potential line of the DC link. The circuit configuration elements other than this are the same as those shown in Figure 1 , and therefore the same reference numerals are affixed to the same circuit configuration elements, and detailed description of the circuit configuration elements will be omitted. Also, as in the first mode, in the second mode, the off resistance of the switching elements in the bridge circuit within the inverter section 12 can be used as the voltage dividing resistors 13-1 and 13-2.

[0091] In the second mode shown in Figure 11 , the insulation resistance value calculation section 19 calculates the insulation resistance value R m of the motor 3 in accordance with Equation 11. In Equation 11, the resistance value of the measurement resistance 14 is set to R in , the value of the positive potential of the DC link at the time when the power conversion operation of the inverter section 12 is stopped, which is measured by the DC link potential measurement section 18, is set to V p .The value of the negative potential of the DC link measured by the DC link potential measuring section 18 at the time when the power conversion operation of the inverter section 12 is stopped is set as V n . In addition, the value of the direct current component of the resistance voltage of the inverter section 12 extracted by the direct current component extracting section 16 (low pass filter) at the time when the power conversion operation is stopped is set as V inL . In addition, the value of the alternating current component of the resistance voltage of the inverter section 12 extracted by the alternating current component extracting section 17 (high pass filter) at the time when the power conversion operation is stopped is set as V inH . In addition, the value V com is set as (V p + V n ) / 2, and the value V dif is set as (V p - V n ) / 2.

[0092] [Equation 11]

[0093]

[0094] Here, the derivation process of Equation 11 used in the calculation processing of the insulation resistance value calculating section 19 in the second mode in which one end of the measuring resistor 14 is connected to the positive potential line of the DC link is described. Figures 12-18 An equivalent circuit for deriving Equation 11 used in the calculation processing of the insulation resistance value calculating section in the second mode is shown.

[0095] In the calculation of the insulation resistance value R m by the insulation resistance value calculating section 19, data measured by the resistance voltage measuring section 15 and the DC link potential measuring section 18 in a state in which the power conversion operation of the inverter section 12 is stopped is used. In the state in which the power conversion operation of the inverter section 12 is stopped, circuits related to the inverter section 12 do not appear in Figures 12-18

[0096] In Figure 12 , the positive potential V p in the positive potential line of the DC link shown in Figure 11 is represented by an equivalent power source 51. Similarly, in Figure 12 , the negative potential V n in the negative potential line of the DC link shown in Figure 3 is represented by an equivalent power source 52. At this time, as shown in Figure 12 , the equivalent power sources 51 and 52 are connected to the voltage dividing resistors 13-1 and 13-2 shown in Figure 11 , the measuring resistor 14, and the insulation resistance 20 of the motor 3. The resistance values of the voltage dividing resistors 13-1 and 13-2 are set as R in ​Set the insulation resistance 20 of motor 3 to R. m The value of the resistance voltage of the measuring resistor 14, measured by the resistance voltage measuring unit 15, is set as V. in .

[0097] exist Figure 12 In the equivalent circuit shown, if Thevenin's theorem is applied to the equivalent power supplies 51 and 52 and the voltage divider resistors 13-1 and 13-2, then we can obtain... Figure 13 The equivalent circuit shown is illustrated. Figure 5 In the equation, the voltage value V6 of the equivalent power supply 54 is represented by Equation 12, and the resistance value of the equivalent resistor 41 is R / 2.

[0098] [Formula 12]

[0099]

[0100] exist Figure 13 In the equivalent circuit shown, if Thevenin's theorem is applied to circuit part T3, then we can obtain... Figure 14 The equivalent circuit shown is illustrated. Figure 14 In the equation, the voltage value V7 of the equivalent power supply 55 is represented by Equation 13, and the resistance value R2 of the equivalent resistor 42 is represented by Equation 14.

[0101] [Formula 13]

[0102]

[0103] [Formula 14]

[0104]

[0105] exist Figure 14 In the equivalent circuit shown, equivalent power supply 53 and equivalent power supply 55 are connected in series via equivalent resistor 42 and measuring resistor 14. Therefore, if equivalent power supply 53 and equivalent power supply 55 are combined into one, we obtain... Figure 15 The equivalent power source 56 is shown. Figure 15 In the equation, the voltage value V8 of the equivalent power source 56 is represented by Equation 15.

[0106] [Formula 15]

[0107]

[0108] exist Figure 15 In the equivalent circuit shown, when the voltage value V8 of the equivalent power supply 56 is divided into differential and in-phase components, the following is obtained: Figure 16 The equivalent power supplies 57 and 58 are shown. In Figure 16 In the equation, the voltage value V9 of the equivalent power source 57 is the differential component, represented by Equation 16. The voltage value V of the equivalent power source 58...10 It is the in-phase component, represented by Equation 17.

[0109] [Formula 16]

[0110]

[0111] [Formula 17]

[0112]

[0113] Figure 16 The equivalent circuit shown can be divided into Figure 17 The equivalent circuit of the DC component shown and Figure 18 The equivalent circuit of the AC component is shown.

[0114] like Figure 17 As shown, in the equivalent circuit for the DC component, an equivalent resistor 42 and a measuring resistor 14 are connected to the equivalent power supply 57 having a differential component V9. The voltage component V applied to the measuring resistor 14 can be determined using Ohm's law. inL Then it is expressed as in Equation 18. In Equation 18, the signal component that does not contain a DC component, i.e. (V p +V n ) / 2 replaced with V com The signal component (V) containing the DC component p -V n ) / 2 replaced with V dif Voltage component V inL This corresponds to the DC component obtained by removing the AC component from the resistance voltage of the measuring resistor 14 measured by the resistance voltage measuring unit 15 through the DC component extraction unit 16 (low-pass filter).

[0115] [Formula 18]

[0116]

[0117] like Figure 18 As shown, in the equivalent circuit of the AC component, for the component V with in-phase component V 10 The equivalent power source 58 is connected to the equivalent resistor 42 and the measuring resistor 14. The voltage component V applied to the measuring resistor 14 can be calculated using Ohm's law. inH Then it is expressed as in Equation 19. In Equation 19, the signal component that does not contain a DC component, i.e. (V p +V n ) / 2 replaced with V com The signal component (V) containing the DC component p -V n ) / 2 replaced with V dif Voltage component V inHAn alternating current component obtained by removing a direct current component from the resistance voltage of the measurement resistor 14 measured by the resistance voltage measurement section 15 through the alternating current component extraction section 17 (high-pass filter).

[0118] [Equation 19]

[0119]

[0120] For the insulation resistance value R m The formula 11 for calculating the insulation resistance value R m is obtained by solving simultaneous equations of the formula 18 and the formula 19. In the second mode in which one end of the measurement resistor 14 is connected to the positive potential line of the DC link, the insulation resistance value calculation section 19 calculates the insulation resistance value R m of the motor 3 according to the formula 11. In the formula 11, the value V com is represented by (V p + V n ) / 2, and the value V dif is represented by (V p - V n ) / 2. V p is the positive potential in the positive potential line of the DC link measured by the DC link potential measurement section 18 at the time when the power conversion operation of the inverter section 12 is stopped. V n is the negative potential in the negative potential line of the DC link measured by the DC link potential measurement section 18 at the time when the power conversion operation of the inverter section 12 is stopped. The direct current component V inL is obtained by removing the alternating current component from the resistance voltage of the measurement resistor 14 measured by the resistance voltage measurement section 15 at the time when the power conversion operation of the inverter section 12 is stopped through the direct current component extraction section 16 (low-pass filter). The alternating current component V inH is obtained by removing the direct current component from the resistance voltage of the measurement resistor 14 measured by the resistance voltage measurement section 15 at the time when the power conversion operation of the inverter section 12 is stopped through the alternating current component extraction section 17 (high-pass filter). For the resistance value R in of the measurement resistor 14, it is sufficient to use a value specified in a specification table or to measure it in advance. In addition, each resistance value R of the voltage dividing resistors 13-1 and 13-2 can be calculated by solving simultaneous equations of the formula 18 and the formula 19. That is, “the insulation resistance value R m of the motor 3 is calculated according to the formula 11” means that “the insulation resistance value R inL of the motor 3 is calculated based on the direct current component V inH of the resistance voltage extracted by the direct current component extraction section 16, the alternating current component V p of the resistance voltage extracted by the alternating current component extraction section 17, and the positive potential V n, to calculate the insulation resistance value R of the motor 3 m

[0121] Further, in the second mode, as to the value V com and the AC component V inH and the value V dif and the DC component V inL , it is also possible to measure after conversion to DC by the rectification circuit. In this case, for example, after rectification of the AC component V inH of the resistance voltage extracted by the AC component extraction section 17, the absolute value is taken, and based on this value, the insulation resistance value R m of the motor 3 is calculated in accordance with Equation 20, or, after rectification of the AC component V inH of the resistance voltage extracted, the absolute value is taken, and after rectification of the DC component V inL of the resistance voltage extracted by the DC component extraction section 16, the absolute value is taken, and based on these values, the insulation resistance value R m of the motor 3 is calculated in accordance with Equation 20. Further, since the absolute values of the AC component V inH of Equation 19 and the DC component V inL of Equation 18 are taken, Equation 20 differs in part of the symbols from Equation 11.

[0122] [Equation 20]

[0123]

[0124] As described above, in either of the first mode and the second mode, the measurement processing of the resistance voltage measurement section 15 and the measurement processing of the DC link potential measurement section 18 are executed in a state in which the power conversion operation of the inverter section 12 is stopped (i.e., a state in which all of the switching elements within the inverter section 12 are turned off), and the insulation resistance value calculation section 19 calculates the insulation resistance value R m based on the data measured at this time. That is, according to the embodiment of the present disclosure, in a state in which the power conversion operation of the inverter section 12 is stopped, the resistance voltage measurement section 15, the DC component extraction section 16, the AC component extraction section 17, the DC link potential measurement section 18, and the insulation resistance value calculation section 19 are caused to operate, whereby it is possible to measure the insulation resistance value R m of the motor 3. Therefore, when measuring the insulation resistance value R m of the motor 3, it is not necessary to disconnect the motor drive device 1 from the AC power supply 2 as in the past. In addition, it is not necessary to provide a circuit breaker between the motor drive device 1 and the AC power supply 2 in order to measure the insulation resistance value R m of the motor 3, and thus the cost is low. Even in a situation in which a circuit breaker is not provided between the motor drive device 1 and the AC power supply 2, it is possible to measure the insulation resistance value R m ​.

[0125] For example, the display unit (not shown) can also display the insulation resistance value R calculated by the insulation resistance value calculation unit 19. m Therefore, the operator can quickly and easily determine the insulation resistance value R of motor 3. m .

[0126] Alternatively, the insulation resistance value R calculated by the insulation resistance value calculation unit 19 can be set to... m The determination unit (not shown) compares the insulation of motor 3 with a threshold value that serves as the basis for judging insulation degradation. The determination unit determines the insulation resistance value R. m If the threshold is exceeded, the display unit will show "Insulation degradation has occurred in motor 3". Examples of display units include standalone display devices, display devices attached to the motor drive unit 1, and display devices attached to personal computers and portable terminals. Alternatively, the operator may be notified of "Insulation degradation has occurred in motor 3" by using an audio device that emits sounds such as voice, loudspeaker, buzzer, or ringtone, either together with or in place of the display unit. This allows the operator to quickly and easily grasp that insulation degradation has occurred in motor 3. Therefore, the operator can easily take countermeasures such as replacing or repairing motor 3.

[0127] The DC component extraction unit 16, AC component extraction unit 17, insulation resistance value calculation unit 19, and upper-level control device can be configured as a combination of analog circuits and an arithmetic processing unit, or as a single arithmetic processing unit, or as a single analog circuit. For example, when the DC component extraction unit 16, AC component extraction unit 17, insulation resistance value calculation unit 19, and upper-level control device are constructed as software programs, the functions of each unit can be realized by causing the arithmetic processing unit to operate according to the software program. Alternatively, the DC component extraction unit 16, AC component extraction unit 17, insulation resistance value calculation unit 19, and upper-level control device can be implemented as semiconductor integrated circuits on which software programs for implementing the functions of each unit are written. Alternatively, the DC component extraction unit 16, AC component extraction unit 17, insulation resistance value calculation unit 19, and upper-level control device can be implemented as a recording medium on which software programs for implementing the functions of each unit are written. In addition, the DC component extraction unit 16, the AC component extraction unit 17, the insulation resistance value calculation unit 19, and the upper control device can be installed in the numerical control device of the machine tool, or in the robot controller that controls the robot.

[0128] The resistance voltage measurement section 15 and the DC link potential measurement section 18 can be constituted by a combination of an analog circuit and an arithmetic processing device, or can be constituted only by an arithmetic processing device, or can be constituted only by an analog circuit. As for the resistance voltage measurement section 15 and the DC link potential measurement section 18, measurement sections that are normally provided in the motor drive device 1 can be used. However, in the calculation of the insulation resistance value R m by the resistance voltage measurement section 15 and the DC link potential measurement section 18 in a state where the power conversion operation of the inverter section 12 is stopped.

[0129] Figure 19 is a flowchart showing an operation flow of the motor drive device according to an embodiment of the present disclosure. Figure 19 The flowchart shown in FIG. 10 can be applied to the motor drive device 1 of either the first mode or the second mode.

[0130] When the insulation resistance value R m of the motor 3 is measured, first, in step S101, the upper-level control device (not shown) stops the power conversion operation of the inverter section 12 by turning off all the switching elements within the inverter section 12.

[0131] In step S102, the resistance voltage measurement section 15 measures the resistance voltage V in that is the potential difference across the measurement resistance 14. A signal related to the resistance voltage V in of the measurement resistance 14 measured by the resistance voltage measurement section 15 is sent to the direct current component extraction section 16 and the alternating current component extraction section 17.

[0132] In step S103, the direct current component extraction section 16 extracts the direct current component V in from the resistance voltage V inL measured by the resistance voltage measurement section 15. A signal related to the direct current component V inL of the resistance voltage extracted by the direct current component extraction section 16 is sent to the insulation resistance value calculation section 19.

[0133] In step S104, the alternating current component extraction section 17 extracts the alternating current component V in from the resistance voltage V inH measured by the resistance voltage measurement section 15. A signal related to the alternating current component V inH of the resistance voltage extracted by the alternating current component extraction section 17 is sent to the insulation resistance value calculation section 19.

[0134] Further, the processing of step S103 and the processing of step S104 can be executed in the order reversed.

[0135] In step S105, the DC link potential measuring section 18 measures the positive potential V p and the negative potential V n in the positive potential line of the DC link. p The signals related to the positive potential V n and the negative potential V inL of the DC link measured by the DC link potential measuring section 18 are sent to the insulation resistance value calculating section 19.

[0136] Further, the processes of steps S102 to S104 and the process of step S105 can be executed in the order reversed.

[0137] In step S106, the insulation resistance value calculating section 19 calculates the insulation resistance value R m of the motor 3 based on the direct current component V inL of the resistance voltage extracted by the direct current component extracting section 16, the alternating current component V inH of the resistance voltage extracted by the alternating current component extracting section 17, and the positive potential V p and the negative potential V n of the DC link measured by the DC link potential measuring section 18. m In the first mode in which one end of the measurement resistance 14 is connected to the negative potential line of the DC link, the insulation resistance value calculating section 19 calculates the insulation resistance value R m of the motor 3 according to Equation 1. m In the second mode in which one end of the measurement resistance 14 is connected to the positive potential line of the DC link, the insulation resistance value calculating section 19 calculates the insulation resistance value R m of the motor 3 according to Equation 11.

[0138] After step S106, for example, the display section (not shown) can be caused to display the insulation resistance value R m calculated by the insulation resistance value calculating section 19. Further, for example, a determination section (not shown) that compares the insulation resistance value R m calculated by the insulation resistance value calculating section 19 with a threshold value that is a criterion for insulation deterioration determination and determines insulation deterioration of the motor 3 can be provided, and in a case where the insulation resistance value R m is determined by the determination section to exceed the threshold value, the display section is caused to display “insulation deterioration of the motor 3 has occurred”. Further, for example, a sound device that emits a sound such as a voice, a sound, a beep, a ring, or the like can be used to notify the operator of “insulation deterioration of the motor 3 has occurred” together with or instead of the display section.

[0139] Figure 20 An example of simulation results of the positive potential and the negative potential of the DC link in a case where an alternating current power source is connected to the motor drive device of an embodiment of the present disclosure by a delta connection is described. As shown in Equation 1 and Equation 11, in calculating the insulation resistance value R m , V inL and V inH are used.p +V n The value V represented by ) / 2 com and by (V) p -V n V represents ) / 2 dif .like Figure 20 As shown, it can be seen that due to the positive potential V p With negative potential V n The difference "V" p -V n "It is constant, so it functions as the DC component, due to the positive potential V." p With negative potential V n The sum of "V" p +V n "It is constant, so it functions as an exchange component."

[0140] Explanation of reference numerals in the attached figures

[0141] 1. Electric motor drive device

[0142] 2 AC power supply

[0143] 3 electric motors

[0144] 4DC link capacitor

[0145] 11 Converter Department

[0146] 12 Inverter Section

[0147] 13-1, 13-2 voltage divider resistors

[0148] 14. Resistance Measurement

[0149] 15 Resistance and Voltage Measurement Section

[0150] 16 DC component extraction unit

[0151] 17 AC Component Extraction Unit

[0152] 18DC Link Potential Measurement Unit

[0153] 19 Insulation Resistance Value Calculation Department

[0154] 20. Insulation resistance of electric motor

[0155] 21, 22 Equivalent resistance

[0156] Equivalent power sources 31, 32, 33, 34, 35, 36, 37, 38

[0157] 41, 42 Equivalent Resistance

[0158] Equivalent power sources for 51, 52, 53, 54, 55, 56, 57, and 58.

Claims

1. An electric motor drive apparatus characterized by comprising: Possessing: a converter section that converts alternating-current power input from an alternating-current power source into direct-current power to output to a DC link; a DC link capacitor provided in the DC link; an inverter section that converts direct-current power in the DC link into alternating-current power for driving a motor to output; a voltage dividing resistor that is two voltage dividing resistors provided in series with each other between a positive potential line and a negative potential line that constitute the DC link, and that connects a connection point of the voltage dividing resistors to a winding of the motor; a measurement resistor connected between the connection point of the voltage dividing resistors and the positive potential line or the negative potential line of the DC link; a resistor voltage measurement section that measures a resistor voltage that is a potential difference across the measurement resistor; a DC component extraction section that extracts a DC component from the resistor voltage measured by the resistor voltage measurement section; an AC component extraction section that extracts an AC component from the resistor voltage measured by the resistor voltage measurement section; a DC link potential measurement section that measures the positive potential in the positive potential line and the negative potential in the negative potential line of the DC link; and a insulation resistance value calculation section that calculates an insulation resistance value of the motor based on the DC component extracted by the DC component extraction section, the AC component extracted by the AC component extraction section, and the positive potential and the negative potential measured by the DC link potential measurement section.

2. The motor drive device according to claim 1, wherein the measurement resistor is connected between the connection point of the voltage dividing resistors and the negative potential line of the DC link.

3. The motor drive device according to claim 1, wherein The resistance value of the measuring resistor is set to R. in The value of the positive potential measured by the DC link potential measuring unit is set as V. p The value of the negative potential measured by the DC link potential measuring unit is set as V. n The value of the DC component extracted by the DC component extraction unit is set as V. inL The value of the AC component extracted by the AC component extraction unit is set as V. inH , value V com Let (V) p +V n ) / 2, the value V dif Let (V) p -V n When ) / 2, the insulation resistance calculation unit calculates the insulation resistance value R of the motor according to the following formula. m , the measurement resistor is connected between the connection point of the voltage dividing resistors and the positive potential line of the DC link.

4. The motor drive device according to any one of claims 1 to 3, wherein the value of the positive potential measured by the DC link potential measuring section is set as V in the value of the negative potential measured by the DC link potential measuring section is set as V p the value of the negative potential measured by the DC link potential measuring section is set as V n the value of the DC component extracted by the DC component extracting section is set as V inL the value of the AC component extracted by the AC component extracting section is set as V inH the value V com is set as (V p + V n ) / 2, and the value V dif is set as (V p - V n ) / 2, the insulation resistance value calculating section calculates the insulation resistance value R m of the motor in accordance with the following equation the voltage dividing resistors are each constituted by a DC link resistor connected in series with each other between the positive potential line and the negative potential line of the DC link.

5. The motor drive device according to any one of claims 1 to 3, wherein the voltage dividing resistors are each constituted by an off-resistance generated when a switching element provided in an upper arm and a lower arm that constitute a bridge circuit in the inverter section is turned off. ​

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