Asynchronous motor rotor broken bar fault online diagnosis method

Abstract

The invention discloses an asynchronous motor rotor broken bar fault online diagnosis method, and relates to the field of fault diagnosis, the asynchronous motor rotor broken bar fault online diagnosis method comprises the following steps: S1, collecting one-phase stator current of an asynchronous motor, and constructing the stator current into a current analysis function; s2, the amplitude square of the current analysis function is calculated, the direct current component of the amplitude square is extracted and filtered out, and a direct current component removed signal with the alternating current component beside the highlighted fault is obtained; compared with the prior art, the method has the beneficial effects that a current analysis function amplitude flat method is adopted, and spectral analysis is carried out after the square of the amplitude of the analysis function is calculated and the direct-current component is filtered, so that the method does not need to depend on the assumed condition that the amplitudes of two side bands are equal and the phases are equal to the fundamental wave phase in the traditional method; even under the condition that sideband component amplitudes and phases are inconsistent, the fault characteristic frequency can still be accurately extracted, and the reliability and applicability of rotor broken bar fault diagnosis are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fault diagnosis, and particularly relates to an online diagnosis method for rotor broken bar fault of an asynchronous motor. BACKGROUND

[0002] The asynchronous motor is widely applied due to its simple structure and low cost, but high humidity, strong vibration, extreme temperature, oil dirt and dust and other harsh environments, and human error in manufacturing and production processes can all cause motor failure problems, and the rotor broken bar fault is one of the typical faults of the squirrel cage asynchronous motor.

[0003] For the rotor broken bar fault of the cage asynchronous motor, the main problem is that the early signal is not obvious and is easily submerged and interfered by the fundamental signal, in the existing diagnosis method, the current analysis function amplitude method constructs a stator current analytical signal and extracts the amplitude for spectrum analysis, but the theory depends on the assumption that the amplitudes of the two sidebands are equal and the phases are equal to the phase of the fundamental wave, which is often not true in actual operation, resulting in that the method fails to diagnose under non-ideal conditions, limiting its engineering applicability, and improvement is needed. SUMMARY

[0004] The present application aims to provide an online diagnosis method for rotor broken bar fault of an asynchronous motor to solve the problems in the background.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: An online diagnosis method for rotor broken bar fault of an asynchronous motor, comprising: Step S1, collecting a phase stator current of the asynchronous motor, constructing the stator current into a current analysis function (analytical signal) to lay a foundation for subsequent amplitude square processing and spectrum analysis; Step S2, calculating the amplitude square of the current analysis function, extracting the direct current component and filtering it out to obtain a signal after removing the direct current component of the fault sideband alternating component (so as to get rid of the consistency of the sideband amplitude and phase in the traditional method); Step S3, performing spectrum analysis on the signal after removing the direct current component, extracting the sideband component amplitude (amplitude at the fault characteristic frequency) and estimating the sideband current amplitude, calculating the sideband current power spectrum, and judging whether the asynchronous motor has rotor broken bar fault through the power spectrum; Step S2 comprises: Step S21, calculating the amplitude square of the current analysis function, used for extracting the sideband frequency component and reducing the influence of the fundamental frequency; Step S22, calculating the direct current component of the amplitude square of the current analysis function (the mean value of the amplitude square) to provide a reference for filtering out the direct current component later; Step S23: Remove the DC component from the square of the amplitude to obtain the signal after removing the DC component, highlighting the AC component of the sideband frequency, which is convenient for spectrum analysis.

[0006] As a further aspect of the present invention: step S1 includes: Step S11, describe the composition of the motor stator current: (1); For power supply base frequency, and This refers to the amplitude and phase of the fundamental frequency current. and Sideband components The amplitude and phase, and Sideband components The amplitude and phase of the signal; Step S12, perform Hilbert transform on the stator current to facilitate the extraction of the signal's amplitude and phase information: (2); Step S13: Using the stator current as the real part and the stator current after Hilbert transformation as the imaginary part, a current analysis function is constructed to facilitate subsequent amplitude analysis and spectrum processing: (3). As a further aspect of the present invention: In step S21, the square of the amplitude of the current analysis function is calculated: (4). As a further aspect of the present invention: In step S22, the DC component of the square of the amplitude of the current analysis function is calculated: (5). As a further aspect of the present invention: in step S23, the DC component in the square of the amplitude is removed to obtain the signal after removing the DC component: (6). As a further aspect of the present invention: step S3 includes: Step S31: Perform spectral analysis on the signal after removing the DC component to obtain the amplitude of the sideband component (the amplitude at the fault sideband frequency, which is convenient for quantifying fault characteristics). Step S32: Divide the sideband component amplitude by twice the stator current amplitude to obtain the sideband current amplitude, which is convenient for assessing the severity of the fault. Step S33: Calculate the side current power spectrum and compare it with the threshold K to determine whether there is a rotor bar breakage fault in the asynchronous motor.

[0007] As a further aspect of the present invention: In step S31, spectral analysis is performed on the signal after removing the DC component to obtain the amplitude of the sideband components. The FFT of the sum of two sinusoidal signals with the same frequency but different amplitudes and phases has an amplitude equal to the sum of the amplitudes of the corresponding phasors of the two sinusoidal signals. Therefore, for... Amplitude-frequency analysis using FFT The amplitude at that point is two The sum of component phasors, i.e. and Multiply the magnitude of the phasor sum by ;Right now: (7). As a further aspect of the present invention: in step S32, the stator current is calculated. amplitude The sideband current amplitude is obtained by dividing the sideband component amplitude by twice the stator current amplitude. (8). As a further aspect of the present invention: in step S33, the sideband current power spectrum is calculated: (9). Compared with the prior art, the beneficial effects of the present invention are: The present invention adopts the amplitude squaring method of current analysis function, and performs spectrum analysis by calculating the square of the amplitude of the analysis function and filtering out the DC component. It does not rely on the assumption that the amplitudes and phases of the two side bands are equal and equal to the phase of the fundamental wave in the traditional method. Even when the amplitudes and phases of the side band components are inconsistent, the fault characteristic frequency can still be accurately extracted, which significantly improves the reliability and applicability of rotor bar breakage fault diagnosis. Attached Figure Description

[0008] Figure 1 This is a flowchart of an online diagnostic method for rotor bar breakage faults in an asynchronous motor. Detailed Implementation

[0009] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0010] Please see Figure 1 An online diagnostic method for rotor bar breakage faults in an asynchronous motor, comprising: Step S1: Collect the stator current of one phase of the asynchronous motor, and construct the stator current into a current analysis function (analytical signal) to lay the foundation for subsequent amplitude square processing and spectrum analysis; Step S2: Calculate the square of the current analysis function, extract the DC component of the square of the amplitude and filter it out to obtain the signal after removing the DC component of the AC component in the sideband of the prominent fault (thus getting rid of the dependence of the traditional method on the consistency of the sideband amplitude and phase). Step S3: Perform spectrum analysis on the signal after removing the DC component, extract the amplitude of the sideband component (amplitude at the fault characteristic frequency) and estimate the amplitude of the sideband current, calculate the power spectrum of the sideband current, and determine whether the asynchronous motor has a rotor bar breakage fault through the power spectrum. Step S2 includes: Step S21: Calculate the square of the current analysis function amplitude to extract sideband frequency components and reduce the influence of the fundamental frequency; Step S22: Calculate the DC component (mean of the square of the amplitude) of the current analysis function to provide a reference for subsequent filtering of DC components; Step S23: Remove the DC component from the square of the amplitude to obtain the signal after removing the DC component, highlighting the AC component of the sideband frequency, which is convenient for spectrum analysis.

[0011] In this embodiment: Please refer to Figure 1 Step S1 includes: Step S11, describe the composition of the motor stator current: (1); For power supply base frequency, and This refers to the amplitude and phase of the fundamental frequency current. and Sideband components The amplitude and phase, and Sideband components The amplitude and phase of the signal; Step S12, perform Hilbert transform on the stator current to facilitate the extraction of the signal's amplitude and phase information: (2); Step S13: Using the stator current as the real part and the stator current after Hilbert transformation as the imaginary part, a current analysis function is constructed to facilitate subsequent amplitude analysis and spectrum processing: (3). In this embodiment: Please refer to Figure 1 In step S21, the square of the magnitude of the current analysis function is calculated: (4). In this embodiment: Please refer to Figure 1 In step S22, the DC component of the square of the current analysis function amplitude is calculated: In this embodiment: Please refer to Figure 1 In step S23, the DC component in the square of the amplitude is removed to obtain the signal after removing the DC component: (6). In this embodiment: Please refer to Figure 1 Step S3 includes: Step S31: Perform spectral analysis on the signal after removing the DC component to obtain the amplitude of the sideband component (the amplitude at the fault sideband frequency, which is convenient for quantifying fault characteristics). Step S32: Divide the sideband component amplitude by twice the stator current amplitude to obtain the sideband current amplitude, which is convenient for assessing the severity of the fault. Step S33: Calculate the side current power spectrum and compare it with the threshold K to determine whether there is a rotor bar breakage fault in the asynchronous motor.

[0012] In this embodiment: Please refer to Figure 1In step S31, spectral analysis is performed on the signal after removing the DC component to obtain the amplitude of the sideband components. The FFT of the sum of two sinusoidal signals with the same frequency but different amplitudes and phases yields an amplitude equal to the sum of the amplitudes of the corresponding phasors of the two sinusoidal signals. Therefore, for... Amplitude-frequency analysis using FFT The amplitude at that point is two The sum of component phasors, i.e. and Multiply the magnitude of the phasor sum by ,Right now: (7). In this embodiment: Please refer to Figure 1 In step S32, the sideband current amplitude is obtained by dividing the sideband component amplitude by twice the stator current amplitude. (8); Calculate the stator current amplitude Stator current Formula (1) has been given; calculate the amplitude. This is a common technique, so I won't go into detail here; it should actually be computation. Amplitude of the fundamental frequency component Considering Amplitude Its fundamental frequency component amplitude The difference is not significant, and the former is simpler to calculate, therefore it is used. Amplitude Replace its fundamental frequency component amplitude In this embodiment: Please refer to Figure 1 In step S33, the power spectrum of the sideband current is calculated: (9). In this invention, the mean of the square of the amplitude of the single-phase current of the motor stator is subtracted from the square of the amplitude before spectral analysis. Compared with the traditional current analysis function amplitude method, which can still accurately detect the sideband spectrum when the condition that the amplitude of the two sidebands is the same and the phase is equal to the phase of the fundamental wave is not met, the traditional current analysis function amplitude has lost its theoretical basis and does not have theoretical completeness.

[0013] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and not restrictive.

[0014] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An online diagnostic method for rotor bar breakage faults in an asynchronous motor, characterized in that, The online diagnostic method for rotor bar breakage faults in this asynchronous motor includes: Step S1: Collect the stator current of one phase of the asynchronous motor, and construct the stator current into a current analysis function to lay the foundation for subsequent amplitude square processing and spectrum analysis. Step S2: Calculate the square of the current analysis function, extract the DC component of the square of the amplitude and filter it out to obtain the signal after removing the DC component from the AC component of the prominent fault. Step S3: Perform spectral analysis on the signal after removing the DC component, extract the amplitude of the sideband component and estimate the amplitude of the sideband current, calculate the power spectrum of the sideband current, and determine whether the asynchronous motor has a rotor bar breakage fault through the power spectrum. Step S2 includes: Step S21: Calculate the square of the current analysis function amplitude to extract sideband frequency components and reduce the influence of the fundamental frequency; Step S22: Calculate the DC component of the square of the current analysis function amplitude to provide a reference for subsequent filtering of DC components; Step S23: Remove the DC component from the square of the amplitude to obtain the signal after removing the DC component, highlighting the AC component of the sideband frequency, which is convenient for spectrum analysis.

2. The online diagnostic method for broken rotor bars in an asynchronous motor according to claim 1, characterized in that, Step S1 includes: Step S11, describe the composition of the motor stator current: (1); For power supply base frequency, and This refers to the amplitude and phase of the fundamental frequency current. and Sideband components The amplitude and phase, and Sideband components The amplitude and phase; Step S12: Perform a Hilbert transform on the stator current to facilitate the extraction of signal amplitude and phase information. （2）； Step S13: Using the stator current as the real part and the stator current after Hilbert transformation as the imaginary part, a current analysis function is constructed to facilitate subsequent amplitude analysis and spectrum processing. （3）。 3. The online diagnostic method for broken rotor bars in an asynchronous motor according to claim 1, characterized in that, In step S21, the square of the magnitude of the current analysis function is calculated: (4).

4. The online diagnostic method for broken rotor bars in an asynchronous motor according to claim 1, characterized in that, In step S22, the DC component of the square of the current analysis function amplitude is calculated: (5).

5. The online diagnostic method for broken rotor bars in an asynchronous motor according to claim 1, characterized in that, In step S23, the DC component in the square of the amplitude is removed to obtain the signal after removing the DC component: (6).

6. The online diagnostic method for rotor bar breakage faults of an asynchronous motor according to any one of claims 1 to 5, characterized in that, Step S3 includes: Step S31: Perform spectral analysis on the signal after removing the DC component to obtain the amplitude of the sideband component; Step S32: Divide the sideband component amplitude by twice the stator current amplitude to obtain the sideband current amplitude, which is convenient for assessing the severity of the fault. Step S33: Calculate the side current power spectrum and compare it with the threshold K to determine whether there is a rotor bar breakage fault in the asynchronous motor.

7. The online diagnostic method for broken rotor bars in an asynchronous motor according to claim 6, characterized in that, In step S31, spectral analysis is performed on the signal after removing the DC component to obtain the amplitude of the sideband components. The FFT of the sum of two sinusoidal signals with the same frequency but different amplitudes and phases yields an amplitude equal to the sum of the amplitudes of the corresponding phasors of the two sinusoidal signals. Therefore, for... Amplitude-frequency analysis using FFT The amplitude at that point is two The sum of component phasors, i.e. and Multiply the magnitude of the phasor sum by ,Right now: (7).

8. The online diagnostic method for broken rotor bars in an asynchronous motor according to claim 6, characterized in that, In step S32, the stator current is calculated. amplitude The sideband current amplitude is obtained by dividing the sideband component amplitude by twice the stator current amplitude. (8).

9. The online diagnostic method for broken rotor bars in an asynchronous motor according to claim 6, characterized in that, In step S33, the power spectrum of the sideband current is calculated: (9).

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