Partial discharge detector

Abstract

To provide a partial discharge detector for detecting partial discharge of a coil without adding a sensor for detecting the partial discharge.SOLUTION: A partial discharge detector includes a thermistor 110b for temperature detection, and extracts components of a first frequency band and a second frequency band corresponding to partial discharge, which is a higher frequency band than the first frequency band, from a signal output by the thermistor 110b so as to detect partial discharge generated in a coil 110a on the basis of the components of both first and second frequency bands.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a partial discharge detection device for a coil. [Background technology]

[0002] The motor system that powers EVs and HEVs consists of a battery, inverter, motor controller, and motor, and the motor is driven by the inverter. The inverter generates the sinusoidal current required to drive the motor by repeatedly switching between the inverter's inputs at high speeds. During this process, a surge voltage exceeding the battery voltage is generated at the inverter's output terminals with each switching operation. This surge voltage propagates through the cable between the inverter and motor and into the motor, momentarily applying a voltage higher than the battery voltage across the motor's coils. This surge voltage varies depending on the motor cable routing, cable length, and operating conditions, and can reach 1.3 times the operating voltage or more. When this surge voltage is applied across the motor's coils, it is known to generate minute electrical discharges called partial discharges through the coil coating. If this partial discharge continues, the erosion of the coil coating will progress, eventually leading to insulation breakdown. Monitoring partial discharges is important for determining whether the coil windings are deteriorating and whether there is a high risk of damage to the windings.

[0003] Against this background, it has become necessary to monitor the insulation performance of motors online.Patent Document 1 describes a partial discharge detection device that uses an antenna-type sensor to detect the current flowing in the ground wire of equipment to which an AC power supply voltage is applied, removes low-frequency components from the detected current, converts it into an envelope signal, and uses this signal, along with the power supply current detected by a current sensor, as inputs to determine whether or not a partial discharge has occurred.Patent Document 2 describes a partial discharge detection device that uses a narrow-band filter to filter a detection signal from a partial discharge sensor installed in the frame of a rotating electric machine, and measures and displays the intensity of the maximum partial discharge level that stably occurs in each cycle of the voltage frequency applied to the stator winding of the peak-detecting rotating electric machine. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-90693 A [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-71742 Summary of the Invention [Problem to be solved by the invention]

[0005] The partial discharge detection devices described in Patent Documents 1 and 2 require the use of a high-frequency current sensor or an RF antenna to detect partial discharges that occur between coils of a rotating electrical machine, but both methods require the sensor to be installed separately inside or near the rotating electrical machine, which increases costs. Furthermore, in order to achieve stable sensitivity, installation locations are limited, and additional work on the housing of the rotating electrical machine is required for installation.

[0006] An object of the present invention is to provide a partial discharge detection device that can detect partial discharge in a coil without adding a sensor for detecting partial discharge. [Means for solving the problem]

[0007] One aspect of the present invention is a partial discharge detection device for a coil, wherein the coil is equipped with a thermistor for temperature detection, and the device extracts components of a first frequency band from a signal output by the thermistor, extracts components of a second frequency band from the signal output by the thermistor that correspond to partial discharges in a high frequency band, and detects partial discharges occurring in the coil based on both the components of the first frequency band and the components of the second frequency band.

[0008] Here, it is preferable to include a high-pass filter that extracts components of the second frequency band corresponding to partial discharge from the voltage output by the thermistor, and a pulse converter that outputs a pulse signal when the output voltage of the high-pass filter is equal to or greater than a predetermined reference value, and to detect partial discharge occurring in the coil based on the pulse signal.

[0009] It is also preferable to include a temperature detection circuit that extracts the components of the first frequency band from the signal output by the thermistor and generates a temperature signal indicating the temperature of the coil, and a signal strength threshold setter that corrects the components of the second frequency band in accordance with the temperature signal, and to detect partial discharges occurring in the coil based on the corrected components of the second frequency band.

[0010] It is also preferable that the coil is provided in a rotating electric machine, the rotating electric machine is rotationally controlled by an inverter, and the rotating electric machine is provided with a partial discharge discriminator that discriminates the occurrence of partial discharge in the coil based on both the components of the first frequency band and the components of the second frequency band in accordance with the timing of the rise or fall of an inverter control signal of the inverter.

[0011] It is also preferable to provide an insulation deterioration level determiner that, when a partial discharge occurring in the coil is detected, determines the insulation deterioration level of the coil depending on the frequency of the partial discharge occurrence.

[0012] It is also preferable to provide an insulation deterioration level determiner that determines the insulation deterioration level of the coil in accordance with the motor current flowing through the coil when a partial discharge occurring in the coil is detected.

[0013] It is also preferable to limit the drive voltage of the coil when a partial discharge occurring in the coil is detected. [Effects of the Invention]

[0014] The partial discharge detection device according to the present invention can detect partial discharge in the coil by using a thermistor for measuring temperature provided in the coil, without adding a separate sensor. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a diagram showing a configuration of a partial discharge detection device according to a first embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the frequency dependence of the dielectric constant and dielectric loss factor of an insulating material. [Figure 3] 2 is a schematic diagram showing the temperature dependence of the dielectric constant and dielectric loss factor of an insulating material. FIG. [Figure 4] FIG. 10 is a diagram showing an example of the temperature dependence of a partial discharge inception voltage. [Figure 5] FIG. 3 is a diagram showing the relationship between the output voltage of the inverter and the current flowing through the rotating electric machine. [Figure 6] FIG. 10 is a diagram showing an example of a waveform of a pulse voltage on which a surge is superimposed. [Figure 7] FIG. 10 is a diagram showing an example of an observed waveform of partial discharge detected by a thermistor. [Figure 8] FIG. 10 is a diagram illustrating a configuration of a partial discharge detection device according to a second embodiment. [Figure 9] FIG. 10 is a diagram illustrating a configuration of a partial discharge detection device according to a third embodiment. [Figure 10] FIG. 10 is a diagram showing the configuration of a partial discharge detection device according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] First Embodiment Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, specific shapes, materials, directions, numerical values, etc. are examples for facilitating understanding of the present invention, and can be appropriately changed according to the application, purpose, specifications, etc. Furthermore, it is originally anticipated that the components of the embodiments and modified examples described below can be selectively combined.

[0017] 1, the partial discharge detection device 100 in the first embodiment is connected to a rotating electric machine 110, an inverter 112, and a motor controller 114. The partial discharge detection device 100 detects partial discharge that may occur in a coil 110a provided in the rotating electric machine 110.

[0018] The rotating electric machine 110 includes a plurality of coils 110a. The rotating electric machine 110 is driven by the output voltage of an inverter 112. The rotating electric machine 110 is mounted on, for example, an electric vehicle, a hybrid electric vehicle, or the like.

[0019] The rotating electric machine 110 includes a thermistor 110b inside the housing. The thermistor 110b is used to detect the temperature inside the housing. The thermistor 110b outputs a voltage signal proportional to the internal temperature of the rotating electric machine 110. In other words, the thermistor 110b outputs a temperature corresponding to the temperature of the coil 110a as a voltage signal.

[0020] The output voltage of the inverter 112 is controlled by, but not limited to, PWM control or one-pulse control. The inverter 112 is configured, for example, as a three-phase inverter circuit in which three arms, each having a power switching element connected in series, are connected in parallel. The inverter 112 is controlled to turn on / off by an inverter control signal output from the motor controller 114. By turning on / off the switching elements constituting the inverter 112, a voltage is applied to the coil 110a of the rotating electric machine 110, and a sinusoidal current flows through the coil 110a.

[0021] The motor controller 114 outputs an inverter control signal to the inverter 112. The inverter control signal is, for example, a PWM control signal. As will be described later, the motor controller 114 receives an output from a temperature detection circuit 10 and an output from a partial discharge determiner 16, and controls the output of the rotating electric machine 110.

[0022] In this embodiment, the rotating electric machine 110 is a motor, and the motor controller 114 is provided as an example. However, if the rotating electric machine 110 is a generator, the motor controller 114 may be a generator controller.

[0023] In a rotating electric machine 110 used as a power source for electric vehicles, hybrid electric vehicles, etc., a sinusoidal current required to drive the rotating electric machine 110 is generated by rapidly repeating the on / off switching operation of the switching elements of the inverter 112. In this case, a surge voltage exceeding the battery voltage is superimposed on the output terminal of the inverter 112 with each switching operation, and this surge voltage propagates to the inside of the motor via the cable between the inverter 112 and the rotating electric machine 110, and a high voltage exceeding the battery voltage is momentarily applied across the coil 110a.

[0024] 2 and 3 are schematic diagrams showing the frequency characteristics and temperature characteristics of the dielectric constant ε' and dielectric loss factor ε" of the dielectric used in the insulating coating material of the coil 110a. In FIGS. 2 and 3, the dielectric constant ε' of the dielectric is shown by a solid line, and the dielectric loss factor ε" of the dielectric is shown by a dashed line.

[0025] The dielectric constant ε' is a value that represents the magnitude of the charge generated by polarization per unit electric field when an electric field is applied to a dielectric; the higher the dielectric constant, the larger the charge generated per unit electric field. Therefore, when an AC electric field is applied to a dielectric, the higher the dielectric constant ε', the greater the power consumption, and this power consumption becomes the dielectric loss factor ε". In both the frequency and temperature characteristics, the dielectric loss factor ε" reaches a maximum at a specific frequency fm or a specific temperature Tm. Furthermore, the dielectric constant ε' exhibits characteristics that increase or decrease around this maximum point.

[0026] For materials that require dielectric strength, a small dielectric constant ε' is desirable. However, as shown in Figure 3, the dielectric constant ε' tends to increase as the environmental temperature rises. In other words, the dielectric strength of an insulating material decreases as the temperature rises. In this way, the temperature characteristics and dielectric strength of a dielectric are closely related, and the partial discharge inception voltage is affected by temperature. In other words, the partial discharge characteristics differ when the temperature differs from room temperature. Specifically, the partial discharge inception voltage exhibits a characteristic of decreasing as the environmental temperature increases, as shown in Figure 4.

[0027] 5 shows the relationship between the output voltage (pulse width) of the inverter 112 and the current flowing through the coil 110a of the rotating electrical machine 110. By modulating the output voltage width of the inverter 112, the output current of the rotating electrical machine 110 is controlled.

[0028] The partial discharge detection device 100 includes a temperature detection circuit 10, a signal intensity threshold setter 11, a high-pass filter 12, a pulse converter 14, a partial discharge discriminator 16, and a PWM edge detector 18. The partial discharge detection device 100 extracts high-frequency components in a high frequency band corresponding to partial discharge from the signal output by the thermistor 110b, extracts low-frequency components in a frequency band lower than the high-frequency components from the signal output by the thermistor 110b, and detects partial discharge occurring in the coil 110a based on both the low-frequency components and the high-frequency components.

[0029] The temperature detection circuit 10 is connected to the thermistor 110b. The temperature detection circuit 10 removes high-frequency components from the voltage signal output from the thermistor 110b and outputs a temperature signal indicating the temperature inside the housing of the rotating electrical machine 110. For example, the temperature detection circuit 10 outputs only a signal in a frequency band of about 10 Hz or less, which is a first frequency band, from the voltage signal output from the thermistor 110b as the temperature signal. The temperature signal is input to the motor controller 114 and the partial discharge determiner 16.

[0030] The motor controller 114 receives a temperature signal from the temperature detection circuit 10 and modulates a control signal for the inverter 112. For example, if the temperature exceeds a predetermined value, the motor controller 114 generates a control signal for the inverter 112 to reduce the rotation speed of the rotating electrical machine 110. However, the control of the motor controller 114 is not limited to this.

[0031] High-pass filter 12 is connected to thermistor 110b. High-pass filter 12 passes only high-frequency components from the voltage signal output from thermistor 110b and outputs a signal containing information about the dielectric constant of the dielectric of coil 110a. High-pass filter 12 outputs, for example, a signal in a second frequency band of approximately 10 MHz or more and several hundred MHz or less from the voltage signal output from thermistor 110b as a detection signal. In other words, high-pass filter 12 extracts high-frequency components of electromagnetic waves due to partial discharge from the voltage signal of thermistor 110b.

[0032] The signal strength threshold setter 11 is connected to the temperature detection circuit 10. Based on the temperature signal output from the temperature detection circuit, the signal strength threshold setter 11 sets a signal strength threshold determined from the temperature characteristics of the partial discharge inception voltage as shown in Fig. 4.

[0033] When a partial discharge occurs, electromagnetic waves generated in coil 110a propagate to thermistor 110b. Thermistor 110b generates a high-frequency voltage change due to a resistance change caused by heat generated when absorbing the electromagnetic waves. High-pass filter 12 passes the high-frequency components specific to partial discharge contained in the output voltage of thermistor 110b and outputs the signal to pulse converter 14.

[0034] The pulse converter 14 extracts the output voltage of the high-pass filter 12 that is equal to or greater than the signal strength threshold output by the signal strength threshold setter 11 and outputs it as a pulse signal. The pulse converter 14 can obtain a peak value from the detection signal output from the high-pass filter 12. The pulse converter 14 can include a comparator 14a and a pulse detector 14b. The comparator 14a detects when the detection signal output from the high-pass filter 12 is greater than the signal strength threshold output by the signal strength threshold setter 11. That is, the comparator 14a outputs the detection signal as is when the detection signal output from the high-pass filter 12 is greater than the signal strength threshold output by the signal strength threshold setter 11, and does not output a signal when the detection signal is less than the signal strength threshold. The pulse detector 14b detects and outputs the peak value of the signal output from the comparator 14a. The detected peak value is input to the partial discharge discriminator 16.

[0035] The partial discharge discriminator 16 receives a signal indicating the peak value output from the pulse converter 14 and determines whether a partial discharge has occurred in the rotating electric machine 110. The partial discharge discriminator 16 receives the temperature signal detected by the temperature detection circuit 10 and the peak value input from the pulse converter 14 to determine whether a partial discharge has occurred. That is, since the partial discharge inception voltage changes depending on the temperature of the rotating electric machine 110, the peak value output from the pulse converter 14 is corrected in accordance with the temperature signal detected by the temperature detection circuit 10 so that the partial discharge discriminator 16 can correctly determine the partial discharge inception voltage. As shown in FIG. 4 , the partial discharge inception voltage of an insulating material generally decreases as the ambient temperature increases, so it is preferable to perform a correction such that the signal intensity threshold is increased as the temperature detected by the temperature detection circuit 10 increases. Note that the specific means of correction is not particularly limited.

[0036] The partial discharge determiner 16 also receives a signal indicating the on / off timing of the switching elements of the inverter 112 from a PWM edge detector 18 that detects the on / off timing of the switching elements of the inverter 112. The PWM edge detector 18 can detect the on / off timing of the switching elements of the inverter 112 based on the phase inversion (voltage inversion) of the control signal of the inverter 112. Partial discharge is more likely to occur as the absolute value of the surge voltage and the voltage change rate increase. That is, partial discharge is more likely to occur at each rising or falling edge of the pulse of the output voltage waveform of the inverter 112, in other words, at the on / off timing of the switching of the inverter 112. Therefore, the partial discharge determiner 16 determines that a partial discharge has occurred in the rotating electric machine 110 when the peak value input from the pulse converter 14 is equal to or greater than a predetermined reference value within a predetermined period from the on / off timing of the switching elements of the inverter 112.

[0037] A signal indicating the partial discharge determination result of the partial discharge determiner 16 is output to the motor controller 114. The motor controller 114 may receive the partial discharge determination result from the partial discharge determiner 16, and when it is determined that a partial discharge has occurred, control the inverter 112 so that the current flowing through the coil 110a of the rotating electric machine 110 is smaller than normal.

[0038] 6 shows an example of a pulse voltage waveform when a surge is superimposed on the pulse voltage output by the inverter 112. The surge voltage is superimposed at the rising and falling timings of the output voltage of the inverter 112.

[0039] Figure 7 shows the output voltage waveform after high-pass filtering of the RF antenna and thermistor 110b at the falling edge of the voltage when the voltage waveform shown in Figure 6 is applied to the rectangular wire. The voltage waveform by the RF antenna is shown for comparison as a conventional method.

[0040] As shown in Fig. 7, a voltage with a large amplitude occurs in the output voltage waveform of the RF antenna near the peak of the surge voltage. In other words, with the conventional method, a large output voltage is observed at the RF antenna, making it possible to detect partial discharge.

[0041] The output voltage waveform of thermistor 110b generates a voltage with a superimposed high frequency wave synchronized with the ringing of the surge voltage. Similar to the output voltage of the RF antenna, this high frequency voltage has the largest amplitude near the peak value of the surge voltage. Therefore, partial discharge can be detected by extracting high frequency components higher than the ringing frequency from the output voltage of thermistor 110b.

[0042] In the partial discharge detection device 100, of the high-frequency voltage, current, light, sound waves, and electromagnetic waves that are generated when partial discharge occurs in the coil 110a of the rotating electric machine 110, the heat that is generated when the electromagnetic waves are absorbed is detected as a resistance change in the thermistor 110b, and the high-pass filter 12 extracts high-frequency components that correspond to the electromagnetic waves during partial discharge from a frequency range higher than the frequency range that corresponds to the temperature signal of the rotating electric machine 110. Then, the pulse converter 14 extracts the peak value of the signal output from the high-pass filter 12, and the partial discharge discriminator 16 discriminates whether or not a partial discharge has occurred based on the peak value.

[0043] As a result, the partial discharge detection device 100 can detect partial discharge using the thermistor 110b that is conventionally provided in the rotating electrical machine 110, without providing a separate RF antenna, high-frequency current sensor, or the like.

[0044] Furthermore, in the partial discharge detection device 100, the partial discharge discriminator 16 corrects the signal strength threshold of the signal strength threshold setter 11 in accordance with the temperature detected by the temperature detection circuit 10, thereby reducing the influence of temperature on the partial discharge inception voltage. This makes it possible to more accurately detect partial discharges that change according to the ambient temperature while reducing the influence of the temperature of the rotating electric machine 110.

[0045] <Second embodiment> 8 shows the configuration of a partial discharge detection device 120 in the second embodiment. Similar to the partial discharge detection device 100 in the first embodiment, the partial discharge detection device 120 is connected to a rotating electric machine 110, an inverter 112, and a motor controller 114. The partial discharge detection device 120 detects partial discharge that may occur in a coil 110a provided in the rotating electric machine 110.

[0046] The partial discharge detection device 120 includes a partial discharge current detector 20, a memory 22, and an insulation deterioration degree determiner 24 in addition to the components of the partial discharge detection device 100. Explanations of the temperature detection circuit 10, signal strength threshold value setter 11, high-pass filter 12, pulse converter 14, partial discharge discriminator 16, and PWM edge detector 18 included in the partial discharge detection device 100 will be omitted except for parts with different functions.

[0047] When a partial discharge is detected, the partial discharge detector 16 outputs a signal indicating that a partial discharge has occurred. The signal indicating that a partial discharge has occurred output from the partial discharge detector 16 is stored in the memory 22.

[0048] The partial discharge current detector 20 receives as input the signal output from the partial discharge determiner 16 and the motor current value obtained from the inverter 112. The partial discharge current detector 20 stores the motor current value when the signal is input from the partial discharge determiner 16 in the memory 22. That is, the partial discharge current detector 20 stores the current value flowing through the rotating electric machine 110 when a partial discharge is occurring in the memory 22. Furthermore, when a signal is input from the partial discharge determiner 16, the partial discharge current detector 20 outputs the signal and a signal indicating the motor current value flowing through the rotating electric machine 110 at that timing to the insulation degradation level determiner 24.

[0049] The insulation degradation level determiner 24 determines the insulation degradation level of the rotating electric machine 110 based on the motor current value data stored in the memory 22 when a signal is input from the partial discharge current detector 20 or at predetermined intervals. The insulation degradation level of the rotating electric machine 110 can be determined, for example, based on the frequency of partial discharge occurrence or the rate of change of the motor current when a partial discharge occurs. Specifically, it can be determined that the higher the frequency of partial discharge occurrence, the more advanced the insulation degradation of the rotating electric machine 110. Furthermore, it can be determined that the smaller the motor current value when a partial discharge occurs, the more advanced the insulation degradation of the rotating electric machine 110. Note that the partial discharge occurrence frequency and the rate of change of the motor current when a partial discharge occurs may be calculated each time a signal is input from the partial discharge current detector 20, or the calculated values may be stored in the memory 22 and updated each time a partial discharge is detected. Furthermore, the insulation degradation level may be determined as a result of whether or not a predetermined degradation threshold is exceeded, or may be a result indicating the degree of insulation degradation at multiple levels.

[0050] The partial discharge detection device 120 of the second embodiment can determine the progress of insulation degradation based on the frequency of partial discharge occurrence and the rate of change of the motor current value when partial discharge occurs, thereby making it possible to determine whether the insulation degradation is within an acceptable level.

[0051] Furthermore, if it is determined that the insulation deterioration has exceeded the allowable level range, a configuration may be adopted in which a warning signal is output to notify that the insulation deterioration has exceeded the allowable range, or the motor output is restricted. For example, a configuration may be adopted in which a notification is made that the insulation performance of the coil 110a in the rotating electric machine 110 has deteriorated. As an example of the notification, in the case of an electric vehicle or a hybrid electric vehicle, an alarm indicating the insulation deterioration of the coil 110a may be displayed on the front panel, or information may be transmitted from the electric vehicle or hybrid electric vehicle to a dealer via a wireless network. The user or dealer who receives the notification can take necessary measures. However, examples of the notification are not limited to these.

[0052] <Third embodiment> 9 shows the configuration of a partial discharge detector 122 according to the third embodiment. The partial discharge detector 122 further includes a motor drive upper limit voltage setter 26 in addition to the components of the partial discharge detector 100 according to the second embodiment.

[0053] Motor drive upper limit voltage setter 26 receives the insulation degradation level output from insulation degradation level determiner 24 and sets a motor drive upper limit voltage for motor controller 114. For example, if insulation degradation level determiner 24 determines that insulation degradation has progressed, it outputs a degradation level determination signal to motor drive upper limit voltage setter 26. Upon receiving the degradation level determination signal, motor drive upper limit voltage setter 26 outputs a voltage limit signal to motor controller 114. Upon receiving the voltage limit signal from motor drive upper limit voltage setter 26, motor controller 114 controls inverter 112 to limit the upper limit of the motor drive voltage to the motor drive upper limit voltage indicated by the voltage limit signal. This makes it possible to suppress the occurrence of partial discharge in rotating electric machine 110.

[0054] Furthermore, if insulation deterioration level determiner 24 determines the degree of insulation deterioration at multiple levels, motor drive upper limit voltage setter 26 may output a voltage limit signal so that the motor drive upper limit voltage corresponds to the level of insulation deterioration. Note that the operation of insulation deterioration level determiner 24 is an example, and does not limit the method of setting the motor drive upper limit voltage according to the degree of insulation deterioration.

[0055] <Fourth embodiment> 10 shows the configuration of a partial discharge detection device 124 according to the fourth embodiment. The partial discharge detection device 124 is configured such that the input to the PWM edge detector 18 in the partial discharge detection device 100 of the first embodiment is changed and a delay circuit 28 is further provided.

[0056] In this embodiment, the PWM edge detector 18 detects the on / off timing of the switching elements of the inverter 112 based on the switching control signal of the inverter 112 from the motor controller 114, and outputs the detected timing to the partial discharge determiner 16. Here, the delay circuit 28 receives the switching control signal output from the motor controller 114, delays the switching control signal, and outputs the delayed signal to the PWM edge detector 18. The delay circuit 28 delays the time from when the switching control signal of the motor controller 114 is input to the inverter 112 to when the switching elements of the inverter 112 are actually turned on / off.

[0057] The line voltage of the inverter 112 is high, and if a DC / DC converter is provided in front of the inverter 112, the configuration of the PWM edge detector 18 in the partial discharge detection device 100 of the first embodiment becomes complex. In the partial discharge detection device 124 of this embodiment, the configuration of the PWM edge detector 18 can be simplified by using the switching control signal of the motor controller 114.

[0058] It should be noted that a similar configuration can be applied to the partial discharge detection device 120 of the second embodiment and the partial discharge detection device 122 of the third embodiment.

[0059] [Configuration of the invention] [Configuration 1] A coil partial discharge detection device, The coil includes a thermistor for detecting temperature. extracting a component of a first frequency band from the signal output by the thermistor; extracting a component of a second frequency band corresponding to partial discharge, which is a high frequency band, from the signal output by the thermistor; A partial discharge detection device that detects partial discharges occurring in the coil based on both the components of the first frequency band and the components of the second frequency band. [Configuration 2] The partial discharge detection device according to configuration 1, a high-pass filter that extracts the second frequency band component corresponding to partial discharge from the voltage output by the thermistor; and a pulse converter that outputs a pulse signal when the output voltage of the high-pass filter is equal to or greater than a predetermined reference value; A partial discharge detection device that detects partial discharges occurring in the coil based on the pulse signal. [Configuration 3] The partial discharge detection device according to configuration 1 or 2, a temperature detection circuit that extracts the component of the first frequency band from the signal output by the thermistor and generates a temperature signal that indicates the temperature of the coil; A partial discharge detection device comprising a signal strength threshold setter that corrects the components of the second frequency band in accordance with the temperature signal, and detects partial discharges occurring in the coil based on the corrected components of the second frequency band. [Configuration 4] The partial discharge detection device according to any one of configurations 1 to 3, The coil is provided in a rotating electric machine, The rotating electric machine is controlled by an inverter, a partial discharge detector that determines whether a partial discharge has occurred in the coil based on both the components of the first frequency band and the components of the second frequency band in accordance with the timing of a rise or fall of an inverter control signal of the inverter. [Configuration 5] The partial discharge detection device according to any one of configurations 1 to 4, A partial discharge detection device characterized by comprising an insulation degradation level determiner that, when a partial discharge occurring in the coil is detected, determines the degree of insulation degradation of the coil depending on the frequency of partial discharge occurrence. [Configuration 6] The partial discharge detection device according to any one of configurations 1 to 4, A partial discharge detection device characterized by comprising an insulation degradation level determiner that determines the insulation degradation level of the coil depending on the motor current flowing through the coil when a partial discharge generated in the coil is detected. [Configuration 7] The partial discharge detection device according to any one of configurations 1 to 6, A partial discharge detection device characterized in that, when a partial discharge occurring in the coil is detected, the drive voltage of the coil is limited. [Explanation of symbols]

[0060] 10 temperature detection circuit, 11 signal strength threshold setter, 12 high-pass filter, 14 pulse converter, 14a comparator, 14b pulse detector, 16 partial discharge discriminator, 18 PWM edge detector, 20 partial discharge current detector, 22 memory, 24 insulation deterioration degree determiner, 26 motor drive upper limit voltage setter, 28 delay circuit, 100, 120, 122, 124 partial discharge detection device, 110 rotating electric machine, 110a coil, 110b thermistor, 112 inverter, 114 motor controller.

Claims

1. A coil partial discharge detection device, The coil includes a thermistor for detecting temperature. extracting a component of a first frequency band from the signal output by the thermistor; extracting a component of a second frequency band corresponding to partial discharge, which is a frequency band higher than the first frequency band, from the signal output by the thermistor; A partial discharge detection device that detects a partial discharge occurring in the coil based on both the components of the first frequency band and the components of the second frequency band.

2. The partial discharge detection device according to claim 1, a high-pass filter that extracts the second frequency band component corresponding to partial discharge from the voltage output by the thermistor; a pulse converter that outputs a pulse signal when the output voltage of the high-pass filter is equal to or greater than a predetermined reference value; A partial discharge detection device that detects partial discharges occurring in the coil based on the pulse signal.

3. The partial discharge detection device according to claim 1, a temperature detection circuit that extracts the component of the first frequency band from the signal output by the thermistor and generates a temperature signal that indicates the temperature of the coil; A partial discharge detection device comprising a signal strength threshold setter that corrects the components of the second frequency band in accordance with the temperature signal, and detects partial discharges occurring in the coil based on the corrected components of the second frequency band.

4. The partial discharge detection device according to claim 1, The coil is provided in a rotating electric machine, The rotating electric machine is controlled by an inverter, a partial discharge detector that determines whether a partial discharge has occurred in the coil based on both the components of the first frequency band and the components of the second frequency band in accordance with the timing of a rise or fall of an inverter control signal of the inverter.

5. The partial discharge detection device according to claim 1, A partial discharge detection device characterized by comprising an insulation degradation level determiner that, when a partial discharge occurring in the coil is detected, determines the degree of insulation degradation of the coil depending on the frequency of partial discharge occurrence.

6. The partial discharge detection device according to claim 1, A partial discharge detection device characterized by comprising an insulation degradation level determiner that determines the insulation degradation level of the coil depending on the motor current flowing through the coil when a partial discharge generated in the coil is detected.

7. The partial discharge detection device according to claim 1, A partial discharge detection device characterized in that, when a partial discharge occurring in the coil is detected, the drive voltage of the coil is limited.

Images