Control device, electrical apparatus, and fault detection method

Abstract

The invention relates to a control device, an electrical apparatus, and a fault detection method. Embodiments provide a control device that detects partial discharge differentially from noise. A control device according to an embodiment includes a control unit and a failure detection unit. The control unit controls the motor. The failure detection unit detects a failure of the motor. The failure detection unit performs frequency analysis of a voltage signal and a current signal for driving the motor. The fault detection unit determines whether or not the current signal includes odd-order harmonics having an odd-order frequency with respect to a fundamental wave of the voltage signal, on the basis of a result of the frequency analysis. The failure detection unit determines, on the basis of the result of the frequency analysis, whether or not the odd-order harmonics have a first phase angle that is a phase angle that is opposite to the phase angle of the fundamental wave.

Description

[0001] This application enjoys priority based on Japanese Patent Application No. 2024-159004 (filed on September 13, 2024). This application incorporates the entire contents of that basic application by reference. Technical Field

[0002] Embodiments of the present invention relate to control devices, electrical equipment, and fault detection methods. Background Technology

[0003] If the insulation performance of an electric motor deteriorates, it can lead to partial discharge, a precursor to insulation failure. Detecting partial discharge helps prevent insulation failure in the motor. Partial discharge is often masked by the noise accompanying motor operation, therefore it needs to be detected separately from the noise. Summary of the Invention

[0004] The problem to be solved by this invention is to detect partial discharge in a way that distinguishes it from noise.

[0005] The control device of this embodiment includes a control unit and a fault detection unit. The control unit controls the motor. The fault detection unit detects faults in the motor. The fault detection unit performs frequency analysis on the voltage and current signals driving the motor. Based on the results of the frequency analysis, the fault detection unit determines whether the current signal contains odd-order higher harmonics with an odd multiple of the frequency of the fundamental frequency of the voltage signal. Based on the results of the frequency analysis, the fault detection unit determines whether the odd-order higher harmonics have a phase angle that is out of phase with respect to the fundamental frequency, i.e., a first phase angle. Attached Figure Description

[0006] Figure 1 This is a diagram schematically illustrating an example of the configuration of the electrical equipment according to the first embodiment.

[0007] Figure 2 This is a functional block diagram illustrating the function of the fault detection unit in the control device of the first embodiment.

[0008] Figure 3 This is a flowchart illustrating the fault detection process performed by the fault detection unit in the first embodiment.

[0009] Figure 4 This is a diagram schematically illustrating an example of the configuration of the electrical equipment according to the second embodiment.

[0010] Figure 5 This is a functional block diagram illustrating the function of the fault detection unit in the control device of the second embodiment.

[0011] Figure 6 This is a flowchart illustrating the fault detection process performed by the fault detection unit in the second embodiment.

[0012] Figure 7 This is a diagram illustrating an example of a waveform that produces a partial discharge relative to the 50Hz power fundamental frequency.

[0013] Figure 8 It means through the Figure 7 The waveform of the signal obtained by bandpass filtering and envelope processing is shown in the figure.

[0014] Figure 9 It means to include Figure 7 The graph shows the frequency analysis results of the sinusoidal current signal of the partial discharge signal.

[0015] Figure 10 It means Figure 8 The graph shows the frequency analysis results of the signal.

[0016] Figure 11 This is a diagram representing a discharge noise signal with a positive charge.

[0017] Figure 12 It means through the Figure 11 The waveform of the signal obtained by bandpass filtering and envelope processing is shown in the figure.

[0018] Figure 13 It means to include Figure 11 The graph shows the frequency analysis results of the sinusoidal current signal of the discharge noise signal.

[0019] Figure 14 It means Figure 12 The graph shows the frequency analysis results of the signal.

[0020] Figure 15 It is a graph showing the phase angles of each higher harmonic when the partial discharge signal is not included in the sinusoidal current signal.

[0021] Figure 16 It is a graph showing the phase angles of each higher harmonic when the discharge noise signal is not included in the sinusoidal current signal.

[0022] Figure 17 This is a diagram schematically representing a first variation of an electrical device.

[0023] Figure 18 This is a diagram schematically representing a second variation of an electrical device.

[0024] Explanation of symbols:

[0025] 1: Electrical equipment; 10: Three-phase AC power supply; 11: Three-phase induction motor; 15: Interrupter; 20: Voltage sensor circuit; 21: Voltage detection circuit; 22: Current sensor circuit; 23: Current detection circuit; 30: Control device; 310: ADC (Analog-to-Digital Converter); 320, 320A: Fault detection unit; 340: Control unit. Detailed Implementation

[0026] Hereinafter, the control device, electrical equipment, and fault detection method of the embodiments will be described with reference to the accompanying drawings.

[0027] Figure 1 This is a schematic diagram illustrating an example of the configuration of the electrical device 1 according to the first embodiment. Figure 1 In this device, electrical equipment 1 has a configuration for controlling a three-phase induction motor 11 that uses a three-phase AC power supply 10.

[0028] like Figure 1 As shown, electrical equipment 1 includes a three-phase AC power supply 10, a three-phase induction motor 11, a circuit breaker 15, a voltage sensor circuit 20, a voltage detection circuit 21, a current sensor circuit 22, a current detection circuit 23, and a control device 30. The three-phase AC power supply 10 is an example of a power supply. The three-phase induction motor 11 is an example of a motor.

[0029] A three-phase AC power supply 10 is connected to a three-phase induction motor 11 via a three-phase wiring connection. The three-phase AC power supply 10 supplies a three-phase AC signal, including the U-phase, V-phase, and W-phase, to the three-phase induction motor 11. The AC signal supplied from the three-phase AC power supply 10 to the three-phase induction motor 11 is the electrical signal that drives the three-phase induction motor 11. The AC signal includes AC voltage signals and AC current signals. These AC voltage signals and AC current signals are examples of the voltage and current signals that drive the motor. Alternatively, the three-phase AC power supply 10 can also be an external component of the electrical equipment 1.

[0030] The three-phase induction motor 11 is driven by an AC signal from a three-phase AC power supply 10. The three-phase induction motor 11 receives and is driven by a three-phase AC signal via a three-phase connection. The three-phase induction motor 11 generates mechanical energy based on the AC signal from the three-phase AC power supply 10. For example, the output shaft of the three-phase induction motor 11 is connected to a load device (not shown) and a drive device (not shown).

[0031] A circuit breaker 15 is installed between the three-phase AC power supply 10 and the three-phase induction motor 11. The circuit breaker 15 controls the supply of AC signals from the three-phase AC power supply 10 to the three-phase induction motor 11 via control from the control device 30. For example, in the event of a fault detected in the three-phase induction motor 11, the circuit breaker 15 cuts off the supply of AC signals from the three-phase AC power supply 10 to the three-phase induction motor 11.

[0032] The voltage sensor circuit 20 is connected to the three-phase wiring. The voltage sensor circuit 20 detects the voltage supplied to each phase wiring that forms the three-phase wiring. For example, the voltage sensor circuit 20 may include a voltage sensor such as a voltage transformer (VT) as a voltage sensor for detecting the voltage of each phase.

[0033] Voltage detection circuit 21 is connected to voltage sensor circuit 20. Voltage detection circuit 21 receives voltage signals corresponding to the detection results of each phase voltage by voltage sensor circuit 20. Based on the detection results of voltage sensor circuit 20, voltage detection circuit 21 detects the state of each phase voltage in the three-phase connection. Voltage detection circuit 21 has the function of converting the signal from voltage sensor circuit 20 into a signal corresponding to the input voltage of ADC 310 of control device 30 described later.

[0034] The current sensor circuit 22 is connected to the three-phase wiring. The current sensor circuit 22 detects the current (phase current) flowing through each phase wiring that forms the three-phase wiring. For example, the current sensor circuit 22 may include a current transformer (CT) or other current sensor as a current sensor for detecting phase current.

[0035] The current detection circuit 23 is connected to the current sensor circuit 22. The current detection circuit 23 receives signals corresponding to the detection results of each phase current by the current sensor circuit 22. Based on the detection results of the current sensor circuit 22, the current detection circuit 23 detects the state of the current in each phase of the three-phase connection. The current detection circuit 23 has the function of performing voltage conversion or impedance matching for applying the signal from the current sensor circuit 22 to the input of the ADC 310 described later.

[0036] The control device 30 controls the internal operation of the electrical equipment 1. In the electrical equipment 1 of this embodiment, the control device 30 includes an ADC (analog-to-digital converter) 310, a fault detection unit 320, and a control unit 340, etc.

[0037] The ADC310 converts various analog signals (analog values) detected within the electrical device 1 into digital signals (digital values). For example, the ADC310 converts signals from the voltage detection circuit 21 and the current detection circuit 23 into digital signals. The signal input to the ADC310 from the voltage detection circuit 21 is substantially the same as the AC voltage signal contained in the AC power signal driving the three-phase induction motor 11. Furthermore, the signal input to the ADC310 from the current detection circuit 23 is substantially the same as the AC current signal contained in the AC power signal driving the three-phase induction motor 11. Therefore, it can be said that the ADC310 converts the AC voltage signal and the AC current signal driving the three-phase induction motor 11 into digital signals.

[0038] The fault detection unit (also known as the fault detection circuit) 320 detects malfunctions of the electrical equipment 1, such as faults in the three-phase induction motor 11 or malfunctions in the three-phase AC power supply 10, based on various signals detected within the electrical equipment 1.

[0039] The control unit (also known as the control circuit) 340 monitors the operating status of each component within the electrical equipment 1 and controls the operation of each component. The control unit 340 controls the function and processing of the fault detection unit 320. The control unit 340 is, for example, a processor.

[0040] Additionally, the control device 30 may further include a memory 390. The memory 390 stores various types of data. For example, the memory 390 stores digital data representing the detection results of AC voltage and AC current signals contained in the AC electrical signals driving the three-phase induction motor 11, as well as programs (software and application programs) for controlling the three-phase induction motor 11.

[0041] In this embodiment, the electrical device 1 uses a three-phase AC power supply 10 as a drive source. While detecting the AC signal supplied from the three-phase AC power supply 10 to the three-phase induction motor 11, the electrical device 1 controls the rotation of the three-phase induction motor 11 via the control device 30.

[0042] For example, in the event of a fault such as overcurrent, short circuit, or grounding in the three-phase induction motor 11, the electrical equipment 1, based on an instruction from the control device 30, cuts off the supply of AC power signals from the three-phase AC power supply 10 to the three-phase induction motor 11 via the interruptor 15. For example, in the event of an abnormality such as phase loss, imbalance, tilt, or surge in the three-phase AC power supply 10, the electrical equipment 1 protects the three-phase induction motor 11 by tripping the interruptor 15 based on an instruction from the control device 30.

[0043] In this embodiment, the electrical device 1 communicates with a host device 9, such as a PLC (Programmable Logic Controller). The host device 9 communicates with control devices 30 of multiple electrical devices 1. Based on the communication results, the host device 9 monitors the operating status of the electrical device 1. For example, the host device 9 monitors periodic power consumption and status signals obtained in real time from the fault detection unit 320. Thus, the host device 9 understands the status of the three-phase induction motor 11 and the status of the load device (not shown) in the electrical device 1.

[0044] Figure 2 This is a functional block diagram illustrating the function of the fault detection unit 320 in the control device 30 of the first embodiment. Additionally, in Figure 2 The diagram illustrates an example of the configuration of a signal processing unit for an AC signal of one phase in a three-phase system. Essentially the same operations are performed for AC signals of the other phases.

[0045] The fault detection unit 320 includes one or more arithmetic logic units (processors) composed of a microcontroller unit (MCU) or an application-specific integrated circuit (ASIC) within the control device 30. The fault detection unit 320 can utilize data and programs stored in the memory 390.

[0046] like Figure 2 As shown, the fault detection unit 320 includes, as a functional block, a first LPF (Low Pass Filter) 321, a first FFT (Fast Fourier Transform) arithmetic unit 322, a first amplitude arithmetic unit 323, a first phase angle arithmetic unit 324, a second LPF 325, a second FFT arithmetic unit 326, a second amplitude arithmetic unit 327, a second phase angle arithmetic unit 328, and an analyzer 329. The functions of the fault detection unit 320 represented by these functional blocks can be implemented in hardware or implemented by executing programs through one or more processors.

[0047] As already explained, the ADC310 converts the AC voltage signal and AC current signal driving the three-phase induction motor 11 into digital signals. In the following description, the AC voltage signal converted to a digital signal is sometimes referred to as "first voltage signal V1," and the AC current signal converted to a digital signal is sometimes referred to as "first current signal C1." The first voltage signal V1 is input to the first LPF321. The first current signal C1 is input to the second LPF325.

[0048] The first LPF321 is a digital low-pass filter that extracts the signal containing frequency components below the first cutoff frequency, i.e., the second voltage signal V2, from the first voltage signal V1. The first LPF321 outputs the second voltage signal V2 to the first FFT arithmetic unit 322.

[0049] The second LPF325 is a digital low-pass filter that extracts the signal containing frequency components below the second cutoff frequency, i.e., the second current signal C2, from the first current signal C1. The second LPF325 outputs the second current signal C2 to the second FFT arithmetic unit 326. The second cutoff frequency can be the same as or different from the first cutoff frequency.

[0050] By using the first LPF321 and the second LPF325, the frequency band of the AC signal processed in the fault detection unit 320 is limited to the frequency band used for monitoring the state of the three-phase induction motor 11. This allows for the suppression of high-order harmonic noise and interference noise contained in the AC signal driving the three-phase induction motor 11. Furthermore, to improve the signal-to-noise ratio (SN ratio) of the AC signal processed in the fault detection unit 320, decimation filters can also be used as the first LPF321 and the second LPF325.

[0051] The first FFT operator 322 performs a Fast Fourier Transform (FFT) on the second voltage signal V2 output from the first LPF 321. As a result of the FFT on the second voltage signal V2, the first FFT operator 322 generates a list representing the correspondence between the frequencies of the multiple sine waves contained in the second voltage signal V2 and the complex numbers representing these sine waves in polar coordinates. In the following description, the list generated by the first FFT operator 322 is sometimes referred to as the "first frequency list L1". The first FFT operator 322 outputs the first frequency list L1 to the first amplitude operator 323 and the first phase angle operator 324.

[0052] The second FFT operator 326 performs a Fast Fourier Transform (FFT) on the second current signal C2 output from the second LPF 325. As a result of the FFT on the second current signal C2, the second FFT operator 326 generates a list representing the correspondence between the frequencies of the multiple sine waves contained in the second current signal C2 and the complex numbers representing these sine waves in polar coordinates. In the following description, the list generated by the second FFT operator 326 is sometimes referred to as the "second frequency list L2". The second FFT operator 326 outputs the second frequency list L2 to the second amplitude operator 327 and the second phase angle operator 328.

[0053] The first FFT operator 322 and the second FFT operator 326 can be implemented by installing software or a hardware accelerator. When the three-phase induction motor 11 is driven at a commercial frequency, it is preferable to obtain an AC signal of 10 to 12 cycles for fast Fourier transform.

[0054] The first amplitude calculator 323 calculates the amplitude of each sine wave contained in the second voltage signal V2 based on the first frequency list L1 output from the first FFT calculator 322. As is known, the amplitude of a sine wave can be calculated by operating on the squares and square roots of the real and imaginary parts contained in a complex number. The first amplitude calculator 323 outputs a first amplitude list L3, which represents the correspondence between the frequencies of each sine wave contained in the second voltage signal V2 and the amplitude of each sine wave, to the analyzer 329.

[0055] The first phase angle calculator 324 calculates the phase angle of each sine wave contained in the second voltage signal V2 based on the first frequency list L1 output from the first FFT calculator 322. As is known, the phase angle of the sine wave can be calculated by using the real and imaginary parts contained in the complex number to perform cotangent calculation. The first phase angle calculator 324 outputs the first phase angle list L4, which represents the correspondence between the frequency of each sine wave contained in the second voltage signal V2 and the phase angle of each sine wave, to the analyzer 329.

[0056] The second amplitude calculator 327 calculates the amplitude of each sine wave contained in the second current signal C2 based on the second frequency list L2 output from the second FFT calculator 326. The second amplitude calculator 327 outputs the second amplitude list L5, which represents the correspondence between the frequency and amplitude of each sine wave contained in the second current signal C2, to the analyzer 329.

[0057] The second phase angle calculator 328 calculates the phase angle of each sine wave contained in the second current signal C2 based on the second frequency list L2 output from the second FFT calculator 326. The second phase angle calculator 328 outputs the second phase angle list L6, which represents the correspondence between the frequency of each sine wave contained in the second current signal C2 and the phase angle of each sine wave, to the analyzer 329.

[0058] The first LPF 321, the first FFT operator 322, the first amplitude operator 323, the first phase angle operator 324, the second LPF 325, the second FFT operator 326, the second amplitude operator 327, and the second phase angle operator 328 are functions of the fault detection unit 320 that perform frequency analysis of the AC voltage signal and AC current signal driving the three-phase induction motor 11. The first amplitude list L3, the first phase angle list L4, the second amplitude list L5, and the second phase angle list L6 are the results of the frequency analysis of the AC voltage signal and AC current signal. In the following description, the first amplitude list L3, the first phase angle list L4, the second amplitude list L5, and the second phase angle list L6 are sometimes referred to as the "first analysis result".

[0059] The analyzer 329 analyzes the state of the three-phase induction motor 11 based on the first analysis result. More specifically, based on the first analysis result, the analyzer 329 determines whether the alternating current signal contains an odd-order higher harmonic that has an odd multiple of the frequency of the fundamental frequency of the alternating voltage signal. As an example, in this embodiment, the odd-order higher harmonic is the third higher harmonic that has a frequency three times that of the fundamental frequency of the alternating voltage signal. For example, the analyzer 329 obtains the frequency associated with the maximum amplitude in the first amplitude list L3 as the frequency of the fundamental frequency of the alternating voltage signal. Then, when the amplitude associated with a frequency three times that of the fundamental frequency of the alternating voltage signal in the second amplitude list L5 is above a predetermined threshold, the analyzer 329 determines that the alternating current signal contains a third higher harmonic.

[0060] Furthermore, based on the first analysis result, the analyzer 329 determines whether the odd-order higher harmonics (3rd higher harmonics) contained in the alternating current signal have a phase angle that is out of phase with respect to the fundamental frequency of the alternating voltage signal, i.e., a first phase angle. As an example, in this embodiment, the first phase angle is a phase angle that is ±90 degrees or more with respect to the fundamental frequency. For example, the analyzer 329 obtains the phase angles associated with the frequency of the fundamental frequency in the first phase angle list L4 as the phase angle of the fundamental frequency. Then, when the phase angle associated with three times the frequency of the fundamental frequency in the second phase angle list L6 is a phase angle that is ±90 degrees or more with respect to the fundamental frequency, the analyzer 329 determines that the odd-order higher harmonics (3rd higher harmonics) contained in the alternating current signal have a first phase angle.

[0061] When the AC current signal contains odd-order higher harmonics (3rd higher harmonics) with a first phase angle, analyzer 329 outputs a partial discharge detection signal D1 indicating that partial discharge of the three-phase induction motor 11 has been detected. When the AC current signal does not contain odd-order higher harmonics, or when the odd-order higher harmonics do not have a first phase angle, analyzer 329 outputs a noise detection signal D2 indicating that interference noise has been detected.

[0062] When a partial discharge occurs in the three-phase induction motor 11, the signal generated by the partial discharge appears as an odd-order higher harmonic in the higher harmonics contained in the AC current signal, which has an odd multiple of the frequency of the fundamental wave of the AC voltage signal. Therefore, when the AC current signal contains odd-order higher harmonics, it is presumed that a partial discharge has occurred in the three-phase induction motor 11. However, when odd-order higher harmonic noise generated by mechanical vibration or from the three-phase AC power supply 10 is mixed into the AC current signal, it is impossible to distinguish whether the odd-order higher harmonics contained in the AC current signal are higher harmonics generated by the partial discharge or higher harmonics generated by the aforementioned interference noise. Therefore, in this embodiment, the fault detection unit 320 is equipped with the function of determining whether the odd-order higher harmonics contained in the AC current signal have a phase angle that is out of phase with respect to the fundamental wave of the AC voltage signal, i.e., a first phase angle. When a partial discharge occurs in the three-phase induction motor 11, the signal generated by the partial discharge appears as an odd-order higher harmonic with a phase angle opposite to the fundamental wave of the AC voltage signal, i.e., a first phase angle. Therefore, the fault detection unit 320 not only determines whether the AC current signal contains odd-order higher harmonics, but also determines whether the odd-order higher harmonics contained in the AC current signal have a first phase angle, thereby distinguishing them from the interference noise described above and detecting the partial discharge.

[0063] Figure 3 This is a flowchart illustrating the fault detection process performed by the fault detection unit 320. The fault detection process described below can be implemented using either hardware or software, or a combination of hardware and software. Furthermore, by performing the fault detection process by the fault detection unit 320, the fault detection method of this embodiment can be implemented.

[0064] like Figure 3 As shown, the fault detection unit 320 performs frequency analysis of the AC voltage signal and AC current signal driving the three-phase induction motor 11 (step S1). Specifically, in step S1, the fault detection unit 320 performs the following processing.

[0065] The fault detection unit 320 extracts a second voltage signal V2, which contains frequency components below the first cutoff frequency, from the AC voltage signal V1 converted into a digital signal, i.e., the first voltage signal V1. The fault detection unit 320 also extracts a second current signal C2, which contains frequency components below the second cutoff frequency, from the AC current signal C1 converted into a digital signal, i.e., the first current signal C1.

[0066] The fault detection unit 320 performs a fast Fourier transform based on the second voltage signal V2, thereby generating a first frequency list L1 that represents the correspondence between the frequencies of the multiple sine waves contained in the second voltage signal V2 and the complex numbers representing these sine waves in polar coordinates.

[0067] The fault detection unit 320 performs a fast Fourier transform based on the second current signal C2, thereby generating a second frequency list L2 that represents the correspondence between the frequencies of the multiple sine waves contained in the second current signal C2 and the complex numbers representing these sine waves in polar coordinates.

[0068] The fault detection unit 320 calculates the amplitude of each sine wave contained in the second voltage signal V2 based on the first frequency list L1, thereby generating a first amplitude list L3 that represents the correspondence between the frequency of each sine wave contained in the second voltage signal V2 and the amplitude of each sine wave.

[0069] The fault detection unit 320 calculates the phase angle of each sine wave contained in the second voltage signal V2 based on the first frequency list L1, thereby generating a first phase angle list L4 that represents the correspondence between the frequency of each sine wave contained in the second voltage signal V2 and the phase angle of each sine wave.

[0070] The fault detection unit 320 calculates the amplitude of each sine wave contained in the second current signal C2 based on the second frequency list L2, thereby generating a second amplitude list L5 that represents the correspondence between the frequency of each sine wave contained in the second current signal C2 and the amplitude of each sine wave.

[0071] The fault detection unit 320 calculates the phase angle of each sine wave contained in the second current signal C2 based on the second frequency list L2, thereby generating a second phase angle list L6 that represents the correspondence between the frequency of each sine wave contained in the second current signal C2 and the phase angle of each sine wave.

[0072] The processing of step S1 described above is the same as that performed by the first LPF 321, the first FFT operator 322, the first amplitude operator 323, the first phase angle operator 324, the second LPF 325, the second FFT operator 326, the second amplitude operator 327, and the second phase angle operator 328, and therefore will not be described in detail here. The fault detection unit 320 obtains the first amplitude list L3, the first phase angle list L4, the second amplitude list L5, and the second phase angle list L6 as the first analysis result by performing the processing of step S1 described above.

[0073] Next, based on the first analysis result, the fault detection unit 320 determines whether the AC current signal contains an odd-numbered higher harmonic with an odd multiple of the frequency of the fundamental frequency of the AC voltage signal (step S2). As already explained, as an example, the odd-numbered higher harmonic in this embodiment is the third higher harmonic with a frequency of 3 times that of the fundamental frequency of the AC voltage signal.

[0074] When the AC current signal contains odd-order higher harmonics (step S2: "Yes"), the fault detection unit 320, based on the first analysis result, determines whether the odd-order higher harmonics (3rd higher harmonic) contained in the AC current signal have a phase angle that is out of phase with respect to the fundamental wave of the AC voltage signal, i.e., a first phase angle (step S3). As already explained, as an example, in this embodiment, the first phase angle is a phase angle with a phase angle of ±90 degrees or more with respect to the fundamental wave.

[0075] Then, when the odd-order higher harmonics (3rd higher harmonics) contained in the AC current signal have a first phase angle (step S3: "Yes"), the fault detection unit 320 outputs a partial discharge detection signal D1 indicating that partial discharge of the three-phase induction motor 11 has been detected (step S4).

[0076] On the other hand, when the AC current signal does not contain odd-order higher harmonics (step S2: "No"), the fault detection unit 320 outputs a noise detection signal D2 indicating that interference noise has been detected (step S5). Furthermore, when the AC current signal contains odd-order higher harmonics, but the odd-order higher harmonics do not have a first phase angle (step S3: "No"), the fault detection unit 320 outputs the noise detection signal D2 (step S5). The processing of steps S2 to S5 is the same as the processing performed by the analyzer 329, and therefore will not be described in detail here.

[0077] As described above, the control device 30 of the first embodiment includes a control unit 340 and a fault detection unit 320. The control unit 340 controls the three-phase induction motor 11. The fault detection unit 320 detects faults in the three-phase induction motor 11. The fault detection unit 320 performs frequency analysis on the AC voltage signal and the AC current signal driving the three-phase induction motor 11. Based on the first analysis result, the fault detection unit 320 determines whether the AC current signal contains odd-order higher harmonics (3rd harmonics) that have an odd multiple of the frequency of the fundamental frequency of the AC voltage signal. Based on the first analysis result, the fault detection unit 320 determines whether the odd-order higher harmonics contained in the AC current signal have a phase angle that is out of phase with respect to the fundamental frequency, i.e., a first phase angle.

[0078] According to the control device 30 of the first embodiment described above, the fault detection unit 320 not only determines whether the alternating current signal contains odd-order higher harmonics, but also determines whether the odd-order higher harmonics contained in the alternating current signal have a first phase angle, thereby enabling partial discharge to be detected in a way that is distinguishable from the odd-order higher harmonic noise mixed into the alternating current signal.

[0079] The fault detection method includes: performing frequency analysis on the AC voltage signal and AC current signal driving the three-phase induction motor 11 (step S1); determining, based on the first analysis result, whether the AC current signal contains odd-order higher harmonics with an odd multiple of the frequency relative to the fundamental wave of the AC voltage signal (step S2); and determining, based on the first analysis result, whether the odd-order higher harmonics contained in the AC current signal have a phase angle that is out of phase relative to the fundamental wave, i.e., the first phase angle (step S3).

[0080] According to the fault detection method described above, it is not only determined whether the AC current signal contains odd-order higher harmonics, but also whether the odd-order higher harmonics contained in the AC current signal have a first phase angle. Thus, partial discharge can be detected in a way that distinguishes it from the odd-order higher harmonic noise mixed into the AC current signal.

[0081] Figure 4 This diagram schematically illustrates an example of the configuration of the electrical device 1 according to the second embodiment. The electrical device 1 of the second embodiment differs from the electrical device 1 of the first embodiment in that the control device 30 includes a fault detection unit 320A that provides additional functions to the fault detection unit 320. Therefore, the fault detection unit 320A, which differs from the first embodiment, will be described in detail below, while other components will be labeled with the same symbols as in the first embodiment, and their descriptions will be omitted or simplified.

[0082] Figure 5 This is a functional block diagram illustrating the function of the fault detection unit 320A in the control device 30 of the second embodiment. Additionally, in Figure 5 The diagram illustrates an example of the configuration of a signal processing unit for an AC signal of one phase in a three-phase system. Essentially the same operations are performed for AC signals of the other phases.

[0083] Similar to the fault detection unit 320 of the first embodiment, the fault detection unit 320A of the second embodiment includes one or more arithmetic units (processors) composed of a microcontroller unit (MCU) or an ASIC within the control device 30. The fault detection unit 320A can utilize data and programs stored in the memory 390.

[0084] like Figure 5 As shown, the fault detection unit 320A includes, as a functional block, a first LPF 321, a first FFT operator 322, a first amplitude operator 323, a first phase angle operator 324, a second LPF 325, a second FFT operator 326, a second amplitude operator 327, and a second phase angle operator 328. These functional blocks are the same as those in the first embodiment, so their description is omitted.

[0085] The fault detection unit 320A, as a functional block, also includes a BPF (Band Pass Filter) 330, an envelope processor 331, a third FFT arithmetic unit 332, a third amplitude arithmetic unit 333, and a third phase angle arithmetic unit 334. Furthermore, the fault detection unit 320A, as a functional block, includes an analyzer 329A that adds additional functions to the analyzer 329. The functions of the fault detection unit 320A represented by these functional blocks can be implemented in hardware or implemented by executing programs through one or more processors.

[0086] In the fault detection unit 320A, the AC current signal C1, converted into a digital signal, is input not only to the second LPF 325 but also to the BPF 330. The BPF 330 is a digital bandpass filter that extracts the third current signal C3, which is a first-frequency signal, from the first current signal C1. As an example, in this embodiment, the BPF 330, with a center frequency around 100kHz, is used to obtain a low-frequency partial discharge waveform. The BPF 330 outputs the third current signal C3 to the envelope processor 331. The third current signal C3 is an example of the first signal.

[0087] Envelope processor 331 generates a fourth current signal C4 by performing envelope processing on the third current signal C3 output from BPF 330. Envelope processor 331 outputs the fourth current signal C4 to the third FFT arithmetic unit 332. The fourth current signal C4 is an example of the second signal.

[0088] The third FFT operator 332 performs a Fast Fourier Transform (FFT) on the fourth current signal C4 output from the envelope processor 331. As a result of the FFT on the fourth current signal C4, the third FFT operator 332 generates a list representing the correspondence between the frequencies of the multiple sine waves contained in the fourth current signal C4 and the complex numbers representing these sine waves in polar coordinates. In the following description, the list generated by the third FFT operator 332 is sometimes referred to as the "third frequency list L7". The third FFT operator 332 outputs the third frequency list L7 to the third amplitude operator 333 and the third phase angle operator 334.

[0089] The third amplitude calculator 333 calculates the amplitude of each sine wave contained in the fourth current signal C4 based on the third frequency list L7 output from the third FFT calculator 332. The third amplitude calculator 333 outputs the third amplitude list L8, which represents the correspondence between the frequency and amplitude of each sine wave contained in the fourth current signal C4, to the analyzer 329A.

[0090] The third phase angle calculator 334 calculates the phase angle of each sine wave contained in the fourth current signal C4 based on the third frequency list L7 output from the third FFT calculator 332. The third phase angle calculator 334 outputs the third phase angle list L9, which represents the correspondence between the frequency of each sine wave contained in the fourth current signal C4 and the phase angle of each sine wave, to the analyzer 329A.

[0091] The third FFT operator 332, the third amplitude operator 333, and the third phase angle operator 334 are functions of the fault detection unit 320A that perform frequency analysis of the fourth current signal C4 (the second signal). The third amplitude list L8 and the third phase angle list L9 are the results of the frequency analysis of the fourth current signal C4. In the following description, the third amplitude list L8 and the third phase angle list L9 are sometimes referred to as "the second analysis result".

[0092] Analyzer 329A analyzes the state of the three-phase induction motor 11 based on the first analysis result and the second analysis result. More specifically, similar to analyzer 329 in the first embodiment, analyzer 329A determines, based on the first analysis result, whether the alternating current signal contains an odd-order higher harmonic with an odd multiple of the frequency of the fundamental frequency of the alternating voltage signal. As an example, the odd-order higher harmonic in this embodiment is the third higher harmonic with a frequency three times that of the fundamental frequency of the alternating voltage signal.

[0093] Furthermore, similar to the analyzer 329 in the first embodiment, the analyzer 329A, based on the first analysis result, determines whether the odd-order higher harmonics (3rd higher harmonics) contained in the alternating current signal have a phase angle that is out of phase with respect to the fundamental wave of the alternating voltage signal, i.e., a first phase angle. As an example, the first phase angle in this embodiment is a phase angle with a phase angle of ±90 degrees or more with respect to the fundamental wave.

[0094] Based on the second analysis result, analyzer 329A determines whether the fourth current signal C4 contains an even-numbered higher harmonic that has an even multiple of the frequency of the fundamental frequency of the AC voltage signal. For example, in this embodiment, the even-numbered higher harmonic is the second higher harmonic that has a frequency twice that of the fundamental frequency of the AC voltage signal. For instance, in the third amplitude list L8, if the amplitude associated with a frequency twice that of the fundamental frequency of the AC voltage signal is above a predetermined threshold, analyzer 329A determines that the fourth current signal C4 contains a second higher harmonic.

[0095] Based on the second analysis result, analyzer 329A determines whether the even-order higher harmonics (2nd higher harmonics) contained in the fourth current signal C4 have a phase angle that is in phase with the fundamental wave of the AC voltage signal, i.e., a second phase angle. As an example, in this embodiment, the second phase angle is a phase angle less than ±90 degrees relative to the fundamental wave. For instance, in the third phase angle list L9, if the phase angle associated with twice the frequency of the fundamental wave is a phase angle less than ±90 degrees relative to the fundamental wave, analyzer 329A determines that the even-order higher harmonics (2nd higher harmonics) contained in the fourth current signal C4 have a second phase angle.

[0096] When the odd-order higher harmonics (3rd higher harmonic) in the alternating current signal have a first phase angle and the even-order higher harmonics (2nd higher harmonic) in the fourth current signal C4 have a second phase angle, the analyzer 329A outputs a partial discharge detection signal D1 indicating that partial discharge has been detected in the three-phase induction motor 11. Otherwise, the analyzer 329A outputs a noise detection signal D2 indicating that interference noise has been detected.

[0097] Similar to the first embodiment, the fault detection unit 320A not only determines whether the AC current signal contains odd-order higher harmonics, but also determines whether the odd-order higher harmonics contained in the AC current signal have a first phase angle. This allows for the detection of partial discharge, distinguishing it from the odd-order higher harmonic noise mixed into the AC current signal. However, when odd-order higher harmonic noise with a first phase angle is mixed into the AC current signal, it is impossible to distinguish whether the odd-order higher harmonics contained in the AC current signal are higher harmonics generated by partial discharge or higher harmonics generated by the aforementioned interference noise. Therefore, in this embodiment, the fault detection unit 320A has the following function: determining whether the even-order higher harmonics contained in the fourth current signal C4 (the second signal), obtained by bandpass filtering and envelope processing of the AC current signal, have a second phase angle, which is in phase with the fundamental wave of the AC voltage signal. In the event of partial discharge in the three-phase induction motor 11, the signal generated by the partial discharge appears in the fourth current signal C4 as an even-order higher harmonic with a phase angle that is in phase with the fundamental wave of the AC voltage signal, i.e., a second phase angle. Therefore, the fault detection unit 320A determines not only whether the odd-order higher harmonics (3rd higher harmonic) contained in the AC current signal have a first phase angle, but also whether the even-order higher harmonics (2nd higher harmonic) contained in the fourth current signal C4 have a second phase angle, thereby enabling the partial discharge to be detected in a way that distinguishes it from the aforementioned interference noise.

[0098] Figure 6 This is a flowchart illustrating the fault detection process performed by the fault detection unit 320A. The fault detection process described below can be implemented using either hardware or software, or a combination of hardware and software.

[0099] like Figure 6 As shown, the fault detection unit 320A performs frequency analysis on the AC voltage signal and AC current signal driving the three-phase induction motor 11 (step S11). The processing performed by the fault detection unit 320A in step S11 is the same as the processing performed by the fault detection unit 320 in step S1 of the first embodiment, so the specific processing of step S11 is omitted. By performing the processing in step S11, the fault detection unit 320A obtains the first amplitude list L3, the first phase angle list L4, the second amplitude list L5, and the second phase angle list L6 as the first analysis result.

[0100] Next, the fault detection unit 320A extracts the third current signal C3 (first signal) of the first frequency band from the AC current signal C1 converted into a digital signal, i.e., the first current signal C1 (step S12). The processing of step S12 is the same as that performed by BPF330, so it will not be described in detail here.

[0101] Next, the fault detection unit 320A generates a fourth current signal C4 (the second signal) by performing envelope processing on the third current signal C3 (step S13). The processing in step S13 is the same as the processing performed by the envelope processor 331, so it will not be described in detail here.

[0102] Next, the fault detection unit 320A performs frequency analysis of the fourth current signal C4 (the second signal) (step S14). Specifically, in step S14, the fault detection unit 320A performs the following processing.

[0103] The fault detection unit 320A performs a fast Fourier transform based on the fourth current signal C4, thereby generating a third frequency list L7 that represents the correspondence between the frequencies of the multiple sine waves contained in the fourth current signal C4 and the complex numbers representing these sine waves in polar coordinates.

[0104] The fault detection unit 320A calculates the amplitude of each sine wave contained in the fourth current signal C4 based on the third frequency list L7, thereby generating a third amplitude list L8 that represents the correspondence between the frequency of each sine wave contained in the fourth current signal C4 and the amplitude of each sine wave.

[0105] The fault detection unit 320A calculates the phase angle of each sine wave contained in the fourth current signal C4 based on the third frequency list L7, thereby generating a third phase angle list L9 that represents the correspondence between the frequency of each sine wave contained in the fourth current signal C4 and the phase angle of each sine wave.

[0106] The processing of step S14 described above is the same as that performed by the third FFT operator 332, the third amplitude operator 333, and the third phase angle operator 334, and therefore will not be described in detail here. The fault detection unit 320A obtains the third amplitude list L8 and the third phase angle list L9 as the second analysis result by performing the processing of step S14 described above.

[0107] Next, based on the first analysis result, the fault detection unit 320A determines whether the AC current signal contains an odd-numbered higher harmonic with an odd multiple of the frequency of the fundamental frequency of the AC voltage signal (step S15). As already explained, as an example, the odd-numbered higher harmonic in this embodiment is the third higher harmonic with a frequency of 3 times that of the fundamental frequency of the AC voltage signal.

[0108] When the AC current signal contains odd-order higher harmonics (step S15: "Yes"), the fault detection unit 320A determines, based on the first analysis result, whether the odd-order higher harmonics (3rd higher harmonic) contained in the AC current signal have a phase angle that is out of phase with respect to the fundamental wave of the AC voltage signal, i.e., a first phase angle (step S16). As already explained, as an example, in this embodiment, the first phase angle is a phase angle with a phase angle of ±90 degrees or more with respect to the fundamental wave.

[0109] When the fault detection unit 320A detects that the odd-order higher harmonics (3rd higher harmonic) contained in the AC current signal have a first phase angle (step S16: "Yes"), it determines, based on the second analysis result, whether the fourth current signal C4 (the second signal) contains an even-order higher harmonic with an even multiple of the frequency of the fundamental frequency of the AC voltage signal (step S17). As already explained, as an example, the even-order higher harmonic in this embodiment is the 2nd higher harmonic with a frequency twice that of the fundamental frequency of the AC voltage signal.

[0110] When the fault detection unit 320A detects that the fourth current signal C4 contains an even-order higher harmonic (step S17: "Yes"), based on the second analysis result, it determines whether the even-order higher harmonic (second higher harmonic) contained in the fourth current signal C4 has a phase angle that is in phase with the fundamental wave of the AC voltage signal, i.e., a second phase angle (step S18). As already explained, as an example, in this embodiment, the second phase angle is a phase angle with a phase angle of less than ±90 degrees relative to the fundamental wave.

[0111] Then, when the even-order higher harmonics (2nd higher harmonics) contained in the 4th current signal C4 have a 2nd phase angle (step S18: "Yes"), the fault detection unit 320A outputs a partial discharge detection signal D1 indicating that partial discharge has been detected in the three-phase induction motor 11 (step S19).

[0112] On the other hand, when the AC current signal does not contain odd-order higher harmonics (step S15: "No"), the fault detection unit 320A outputs a noise detection signal D2 (step S20). Furthermore, when the AC current signal contains odd-order higher harmonics, but the odd-order higher harmonics do not have a first phase angle (step S16: "No"), the fault detection unit 320A outputs a noise detection signal D2 (step S20). Additionally, when the AC current signal contains odd-order higher harmonics with a first phase angle, but the fourth current signal C4 does not contain even-order higher harmonics (step S17: "No"), the fault detection unit 320A outputs a noise detection signal D2 (step S20). Furthermore, when the AC current signal contains odd-order higher harmonics with a first phase angle and the fourth current signal C4 contains even-order higher harmonics, but the even-order higher harmonics do not have a second phase angle (step S18: "No"), the fault detection unit 320A outputs a noise detection signal D2 (step S20). The processing of steps S15 to S20 is the same as the processing performed by the analyzer 329A, and therefore will not be described in detail here.

[0113] As described above, the control device 30 of the second embodiment includes a control unit 340 and a fault detection unit 320A. The control unit 340 controls the three-phase induction motor 11. The fault detection unit 320A detects faults in the three-phase induction motor 11. The fault detection unit 320A performs frequency analysis on the AC voltage signal and the AC current signal driving the three-phase induction motor 11. Based on the first analysis result, the fault detection unit 320A determines whether the AC current signal contains an odd-order higher harmonic (3rd harmonic) with an odd multiple of the frequency of the fundamental frequency of the AC voltage signal. Based on the first analysis result, the fault detection unit 320A determines whether the odd-order higher harmonic contained in the AC current signal has a phase angle that is out of phase with respect to the fundamental frequency, i.e., a first phase angle. Furthermore, the fault detection unit 320A extracts a first signal (3rd current signal C3) of the first frequency band from the AC current signal. The fault detection unit 320A generates a second signal (4th current signal C4) by performing envelope processing on the first signal. The fault detection unit 320A performs frequency analysis on the second signal. Based on the results of the second analysis, the fault detection unit 320A determines whether the second signal contains even-numbered higher harmonics with an even-numbered multiple of the fundamental frequency. Based on the results of the second analysis, the fault detection unit 320A determines whether the even-numbered higher harmonics contained in the second signal have a phase angle that is in phase with the fundamental frequency, i.e., a second phase angle.

[0114] According to the second embodiment described above, the fault detection unit 320A not only determines whether the odd-order higher harmonics (3rd higher harmonics) contained in the alternating current signal have a first phase angle, but also determines whether the even-order higher harmonics (2nd higher harmonics) contained in the second signal (4th current signal C4) have a second phase angle, thereby enabling the partial discharge to be detected in a way that distinguishes it from the odd-order higher harmonic noise with a first phase angle.

[0115] Figures 7 to 16 The results of the analysis using simulated waveforms are shown to clarify the effects of the above implementation method. Figure 7 This is a diagram illustrating an example of a partial discharge waveform generated relative to the 50Hz power supply fundamental frequency. The partial discharge waveform is a simulation of the phenomenon centered at positions with a phase of 45 degrees and 225 degrees relative to the power supply fundamental frequency, with a half-amplitude of a few μs. Figure 8 It means through the Figure 7 The waveform of the signal obtained by bandpass filtering and envelope processing is shown in the figure.

[0116] Figure 9 It means to include Figure 7 The graph shows the frequency analysis results of the sinusoidal current signal of the partial discharge signal. Figure 10 It means Figure 8 The graph shows the frequency analysis results of the signal. (See figure.) Figure 9 As shown, the partial discharge signal appears as odd-order higher harmonics such as the 3rd and 5th orders relative to the power supply fundamental frequency (50Hz). On the other hand, as... Figure 10 As shown, in the signal obtained by bandpass filtering and envelope processing of the sinusoidal current signal, the partial discharge signal appears as even-order higher harmonics such as the 2nd and 4th relative to the power supply fundamental frequency.

[0117] In order to include Figure 7 The states of the sinusoidal current waveform of the partial discharge signal shown are compared, and in Figure 11 The diagram shows a discharge noise signal with a positive charge. The partial discharge signal generates a current relative to the ground potential, but is supplemented with a current carrying a certain charge as interference noise. Figure 12 It means through the Figure 11 The waveform of the signal obtained by bandpass filtering and envelope processing is shown in the figure.

[0118] Figure 13 It means to include Figure 11 The graph shows the frequency analysis results of the sinusoidal current signal of the discharge noise signal. Figure 14 It means Figure 12 The graph shows the frequency analysis results of the signal. (See figure.) Figure 13As shown, the discharge noise signal appears as even-order higher harmonics such as the 2nd and 4th orders relative to the power supply fundamental frequency (50Hz). On the other hand, as... Figure 14 As shown, in the signal obtained by bandpass filtering and envelope processing of the sinusoidal current signal containing discharge noise signal, the discharge noise signal appears as even-order higher harmonics such as the 2nd and 4th order relative to the power supply fundamental frequency.

[0119] Figure 7 as well as Figure 11 The difference in the recorded sinusoidal current waveforms lies in the difference between the current signal generated relative to ground potential and the current signal with a certain potential. Therefore, when... Figure 9 as well as Figure 13 When comparing the results of the recorded frequency analysis, the partial discharge signal appears as an odd-order higher harmonic after the 3rd order, but the discharge noise appears as an even-order higher harmonic after the 2nd order.

[0120] Figure 15 This is a graph showing the phase angles of the higher harmonics when the partial discharge signal is contained within a sinusoidal current signal. Figure 15 In the diagram, θ1 is the phase angle of the third harmonic appearing in the sinusoidal current signal containing the partial discharge signal. θ2 is the phase angle of the second harmonic appearing in the signal obtained by bandpass filtering and envelope processing of the sinusoidal current signal containing the partial discharge signal. For comparison, the phase angle θ0 of the power supply fundamental is also shown in section 15.

[0121] like Figure 15 As shown, the partial discharge signal appears as an odd-order higher harmonic in the sinusoidal current signal, with a phase angle θ1 that is out of phase with respect to the fundamental power supply wave θ0. Phase angle θ1 is a phase angle greater than ±90 degrees relative to the fundamental power supply wave θ0. Furthermore, in the signal obtained by bandpass filtering and envelope processing of the sinusoidal current signal, the partial discharge signal appears as an even-order higher harmonic, with a phase angle θ2 that is in phase with respect to the fundamental power supply wave θ0. Phase angle θ2 is a phase angle less than ±90 degrees relative to the fundamental power supply wave θ0.

[0122] Figure 16 This is a graph showing the phase angles of each higher harmonic when the discharge noise signal is contained within a sinusoidal current signal. Figure 16 In the above, θ3 is the phase angle of the second harmonic appearing in the sinusoidal current signal containing discharge noise. θ4 is the phase angle of the second harmonic appearing in the signal obtained by bandpass filtering and envelope processing of the sinusoidal current signal containing discharge noise. For comparison, in... Figure 16The phase angle θ0 of the fundamental wave of the power supply is also shown.

[0123] like Figure 16 As shown, the discharge noise signal appears in the sinusoidal current signal as an even-order higher harmonic with a phase angle θ3 that is in phase with the fundamental power supply wave relative to phase angle θ0. Furthermore, in the signal obtained by bandpass filtering and envelope processing of the sinusoidal current signal, the discharge noise signal appears as an even-order higher harmonic with a phase angle θ4 that is in phase with the fundamental power supply wave relative to phase angle θ0.

[0124] Based on the simulation analysis results above, the partial discharge signal appears as an odd-order higher harmonic within the higher harmonics of the sinusoidal current signal, having an odd multiple of the frequency relative to the fundamental frequency of the power supply. Therefore, when the sinusoidal current signal contains odd-order higher harmonics, it is presumed that partial discharge has occurred. However, when odd-order higher harmonic noise is mixed into the sinusoidal current signal as interference noise, it is impossible to distinguish whether the odd-order higher harmonics contained in the sinusoidal current signal are higher harmonics generated by partial discharge or higher harmonics generated by the aforementioned interference noise. On the other hand, the partial discharge signal appears as an odd-order higher harmonic with a phase angle that is out of phase relative to the fundamental frequency of the power supply, i.e., a first phase angle. Therefore, by determining not only whether the sinusoidal current signal contains odd-order higher harmonics, but also whether such odd-order higher harmonics have a first phase angle, partial discharge can be detected in a way that distinguishes it from the aforementioned interference noise.

[0125] When odd-order higher harmonic noise with a first phase angle is mixed into a sinusoidal current signal, the above-described determination alone cannot distinguish whether the odd-order higher harmonics in the sinusoidal current signal are caused by partial discharge or by interference noise. In the signal (second signal) obtained by bandpass filtering and envelope processing of the sinusoidal current signal, the partial discharge signal appears as an even-order higher harmonic with a second phase angle that is in phase with the fundamental wave of the power supply. Therefore, by determining not only whether the odd-order higher harmonics in the sinusoidal current signal have a first phase angle, but also whether the even-order higher harmonics in the second signal have a second phase angle, partial discharge can be detected in a way that distinguishes it from the odd-order higher harmonic noise with a first phase angle.

[0126] Figure 17 This is a schematic diagram illustrating a first variation of electrical equipment 1. (As shown...) Figure 17As shown, the electrical device 1 of the first modification includes a power conversion device 40. The power conversion device 40 drives a three-phase induction motor 11 by converting the power from the three-phase AC power supply 10. The power conversion device 40 includes a rectifier circuit 410, a switching circuit 420, and a smoothing capacitor 430.

[0127] The rectifier circuit 410 rectifies the supplied AC voltage. The rectifier circuit 410 outputs a rectified voltage (DC voltage). The rectifier circuit 410 includes multiple diodes 411. Two diodes 411 are connected in series between the high-potential side node and the low-potential side node of the power conversion device 40. The two series-connected diodes 411 form a bridge arm. Multiple bridge arms are connected in parallel. The rectifier circuit 410 includes three bridge arms corresponding to the U-phase, V-phase, and W-phase of the three-phase AC power supply 10.

[0128] The smoothing capacitor 430 smooths the voltage (DC voltage) output from the rectifier circuit 410. The smoothing capacitor 430 is connected in parallel with respect to the rectifier circuit 410 and the switching circuit 420 between the high-potential side node and the low-potential side node of the power conversion device 40.

[0129] The switching circuit 420 converts the supplied DC voltage into AC voltage. The switching circuit 420 includes multiple switching elements 421. Each switching element 421 includes an IGBT (Insulated Gate Bipolar Transistor) and a diode. Two switching elements 421 are connected in series between the high-potential side node and the low-potential side node of the power conversion device 40. The two series-connected switching elements 421 form a bridge arm. Multiple bridge arms are connected in parallel. The switching circuit 420 includes three bridge arms corresponding to the U-phase, V-phase, and W-phase of the three-phase induction motor 11.

[0130] The power conversion device 40 may include other components such as a DC reactor (not shown).

[0131] The three-phase AC power supply 10 is connected to the rectifier circuit 410 of the power conversion device 40. The wiring of each phase of the three-phase AC power supply 10 is connected to the corresponding one of the three arms of the rectifier circuit 410.

[0132] The three-phase induction motor 11 is connected to the switching circuit 420 of the power conversion device 40. The wiring of each phase of the three-phase induction motor 11 is connected to one of the corresponding arms of the three bridge arms of the switching circuit 420.

[0133] Voltage sensor circuit 20A detects the state of the voltage signal of each phase of the three-phase AC power supply 10. Voltage sensor circuit 20A monitors the input power supply voltage.

[0134] Voltage sensor circuit 20B detects the state of the DC voltage output from rectifier circuit 410. Voltage sensor circuit 20B monitors the rectified DC voltage.

[0135] The voltage detection circuit 21 transmits the voltage signal, representing the detection results of the voltage sensor circuits 20A and 20B, to the control device 30. The voltage signal is an analog signal.

[0136] The current sensor circuit 22 detects the drive current output from the switching circuit 420. The current sensor circuit 22 monitors the value of the drive current supplied to the three-phase induction motor 11.

[0137] The current detection circuit 23 transmits a current signal, representing the detection result of the current sensor circuit 22, to the control device 30. The current signal is an analog signal.

[0138] The driver control circuit 25 generates a PWM (pulse width modulation) signal or a PAM (pulse amplitude modulation) signal according to the instruction from the control device 30. The driver control circuit 25 sends the PWM signal or PAM signal to each switching element 421 of the switching circuit 420. Thus, the driver control circuit 25 drives the switching elements 421 of the switching circuit 420. The driver control circuit 25 is connected to the gate (control terminal) of each switching element 421.

[0139] The control device 30 converts the analog signals transmitted from the voltage detection circuit 21 and the current detection circuit 23 into digital signals via the ADC 310. The resulting digital signals are used to control the power conversion device 40.

[0140] The control device 30 generates a command signal for controlling the rotation state of the three-phase induction motor 11 based on instructions from the host device 9. The control device 30 transmits the generated command signal to the driver control circuit 25. Thus, the control device 30 controls the operation of the three-phase induction motor 11 via the driver control circuit 25.

[0141] The fault detection unit 320 of the control device 30 acquires digital signals corresponding to the detection results of the voltage sensor circuits 20A and 20B, and digital signals corresponding to the detection results of the current sensor circuit 22. Thus, the fault detection unit 320 stably monitors the status of the power conversion device 40 and the status of the three-phase induction motor 11.

[0142] Figure 18 This is a schematic diagram illustrating a second variation of electrical equipment 1. (As shown...) Figure 18As shown, the host device 9 can replace the fault detection unit 320 to perform the partial discharge detection process. That is, the fault detection unit 320 in the electrical equipment 1 only has the function of communicating various electrical signals in the electrical equipment 1 to the host device 9.

[0143] like Figure 18 As shown, the host device 9 has a fault detection unit 320X. The host device 9 performs various processes for detecting partial discharge based on the signal from the fault detection unit 320 of the electrical device 1 via the fault detection unit 320X.

[0144] Therefore, the host device 9 can monitor the fault status of the electrical equipment 1 from the outside. Thus, the host device 9 functions as a control device for the three-phase induction motor 11 and the electrical equipment 1. Various functions installed in the host device 9 as the fault detection unit 320 are installed and activated via software as algorithms and analysis methods.

[0145] Therefore, in a system (network) including electrical equipment 1 and host device 9, the computational load of the edge device (electrical equipment 1) is reduced. When the functions for performing various processes for detecting the aforementioned partial discharge are installed in an existing system, as in this modified example, the host device 9, which is capable of performing partial discharge detection processing, does not need to attach the fault detection unit 320 to the existing electrical equipment, and the entire system can be used with high scalability.

[0146] According to at least one embodiment described above, a control device can be provided, which includes a control unit for controlling an electric motor and a fault detection unit for detecting faults in the electric motor. The fault detection unit performs frequency analysis on the voltage signal and current signal of the drive motor. Based on the result of the frequency analysis, it determines whether the current signal contains an odd-order higher harmonic with an odd multiple of the frequency of the fundamental wave of the voltage signal. Based on the result of the frequency analysis, it determines whether the odd-order higher harmonic has a phase angle that is out of phase with respect to the fundamental wave, i.e., a first phase angle. Thus, partial discharge can be detected in a way that distinguishes it from noise.

[0147] The functions of the elements disclosed in this specification can be implemented using general-purpose processors, special-purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), FPGAs (Field Programmable Gate Arrays), existing circuits, and / or, combinations thereof, circuitry or processing circuitry, which is programmed by one or more programs stored in one or more memories or otherwise configured to perform the disclosed functions. A processor includes transistors and other circuitry and is therefore considered processing circuitry or circuitry. A processor can also be a programmed processor that executes a program stored in memory. In this invention, a circuit, unit, or device is hardware that performs the listed functions, or hardware programmed to perform the listed functions. The hardware is the hardware disclosed in this specification and can be any hardware as long as it is programmed or configured to perform the listed functions.

[0148] It has a memory that stores a computer program containing computer instructions. These computer instructions provide logic and routines that enable hardware (e.g., processing circuitry or circuitry) to perform the methods disclosed in this specification. The computer program can be installed in a generally known form as a computer-readable storage medium, a computer program product, a memory device, a storage medium such as a CD-ROM and DVD, and / or the memory of an FPGA and ASIC.

[0149] Several embodiments of the present invention have been described. These embodiments are provided by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, and are included in the scope of the invention described in the claims and its equivalents.

Claims

1. A control device comprising: The control unit controls the electric motor; and The fault detection department detects faults in the aforementioned motors. The aforementioned fault detection department is, Frequency analysis was performed on the voltage and current signals driving the aforementioned motor. Based on the results of the frequency analysis above, it is determined whether the current signal contains odd-numbered higher harmonics with an odd-numbered multiple of the fundamental frequency of the voltage signal. Based on the results of the frequency analysis above, it is determined whether the above odd-order higher harmonics have a phase angle that is out of phase with respect to the above fundamental wave, i.e., the first phase angle.

2. The control device according to claim 1, wherein, The aforementioned odd-numbered higher harmonics are the third higher harmonics, which have a frequency three times that of the fundamental wave.

3. The control device according to claim 1, wherein, The first phase angle mentioned above is a phase angle that is ±90 degrees or more relative to the fundamental wave.

4. The control device according to claim 1, wherein, The aforementioned fault detection unit outputs a partial discharge detection signal indicating that partial discharge has been detected in the motor when the odd-order higher harmonics have the aforementioned first phase angle.

5. The control device according to claim 1, wherein, The aforementioned fault detection department is, Extract the first signal of the first frequency band from the above current signal. The second signal is generated by performing envelope processing on the first signal mentioned above. Perform frequency analysis on the second signal mentioned above. Based on the frequency analysis results of the second signal, it is determined whether the second signal contains even-numbered higher harmonics with an even-numbered multiple of the frequency of the fundamental wave. Based on the frequency analysis of the second signal, it is determined whether the even-order higher harmonics have a phase angle that is in phase with the fundamental wave, i.e., the second phase angle.

6. The control device according to claim 5, wherein, The aforementioned even-order higher harmonics are the second-order higher harmonics with a frequency twice that of the aforementioned fundamental wave.

7. The control device according to claim 5, wherein, The second phase angle mentioned above is a phase angle that is less than ±90 degrees relative to the fundamental wave.

8. The control device according to claim 5, wherein, The aforementioned fault detection unit outputs a partial discharge detection signal indicating that partial discharge has been detected in the motor when the odd-order higher harmonics have the first phase angle and the even-order higher harmonics have the second phase angle.

9. An electrical device comprising: An electric motor, connected to a power source; and The control device according to claim 1 controls the aforementioned electric motor.

10. A fault detection method, comprising: Perform frequency analysis on the voltage and current signals of the drive motor; Based on the results of the frequency analysis above, it is determined whether the current signal contains odd-numbered higher harmonics with an odd-numbered multiple of the fundamental frequency of the voltage signal; and Based on the results of the frequency analysis above, it is determined whether the above odd-order higher harmonics have a phase angle that is out of phase with respect to the above fundamental wave, i.e., the first phase angle.

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