A Detection Method for Inter-Turn Short Circuit Fault of Asynchronous Motor Stator

Abstract

The present invention discloses a method for detecting the inter-turn short circuit fault of the stator of an asynchronous motor, comprising the following steps: Step S1, collecting the motor speed and the stator current signal of the asynchronous motor. Step S2, screening the stator current signal of the asynchronous motor in Step S1 to confirm the original stator current signal of the asynchronous motor. Step S3, processing the original stator current signal obtained in Step S2 to extract the frequency and amplitude of the harmonic components of the inter-turn short circuit fault of the stator; Step S4, setting a reference value for the amplitude increment, comparing the amplitude changes of the characteristic frequencies extracted in Step S3 to determine whether to issue an alarm or end. In the present invention, first, the hardware circuit is simplified, then the empirical mode decomposition is used to preliminarily extract the fault characteristic frequencies to avoid interference from other faults, further highlight the fault characteristic frequencies and weaken the influence of spectral leakage, and finally judge whether the current signal is abnormal through the change of the amplitude of the fault characteristic frequencies, ensuring the safe and reliable operation of the motor.

Description

Technical Field

[0001] The present invention relates to the field of motor fault detection, and particularly to a method for detecting stator inter-turn short circuit faults of an asynchronous motor. Background Art

[0002] Asynchronous motors are a commonly used power device because of their simple structure and low cost, and are indispensable in life and production activities. Maintaining the safe and reliable operation of motors is related to all aspects of people's production and life. Stator winding inter-turn short circuit is a common fault of asynchronous motors, and it will cause other faults. The influence on the motor current in the early stage of the fault is small and difficult to observe. It is difficult to accurately detect the fault by directly performing spectral analysis on the current signal. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for detecting stator inter-turn short circuit faults of an asynchronous motor, which can perform on-line detection on the asynchronous motor, timely alarm the stator inter-turn faults, prevent them from developing into serious faults, and ensure the reliable operation of the motor, and can solve one or more of the above technical problems.

[0004] In order to achieve the above purpose, the technical solution proposed by the present invention is as follows:

[0005] A method for detecting stator inter-turn short circuit faults of an asynchronous motor includes the following steps:

[0006] Step S1, collecting the motor speed and the stator current signal of the asynchronous motor;

[0007] Step S2, conditioning the stator current signal of the asynchronous motor in step S1 to confirm the original stator current signal of the asynchronous motor;

[0008] Step S3, processing the original stator current signal of the asynchronous motor obtained in step S2 to extract the frequency and amplitude of the harmonic components of the stator inter-turn short circuit fault;

[0009] Step S4, setting a reference value for the amplitude increment, comparing the amplitude change of the characteristic frequency extracted in step S3, and determining whether to issue an alarm or end.

[0010] Further, the specific process of step S1 is as follows:

[0011] Step S11, collecting the speed n1 of the asynchronous motor, calculating the slip ratio s and the theoretical value f of the frequency of the stator inter-turn short circuit fault harmonics st ;

[0012] where s = (n0 - n1) / n0, and n0 is the synchronous speed.

[0013] The theoretical value calculation formula for the frequency of the stator inter-turn short circuit fault harmonics of the asynchronous motor is p is the number of pole pairs of the asynchronous motor, s is the slip ratio, f0 is the fundamental frequency of the power supply, k is a positive integer, and n is the rotor harmonic order;

[0014] Step S12, preset a frequency reference value f0 is the fundamental frequency of the power supply, n is the rotor harmonic order, p is the number of pole pairs of the asynchronous motor, and k is a positive integer;

[0015] Step S13, set the sampling frequency f of the data acquisition card s = mf r and the number of sampling points N = t×f s , where m is the number of sampling points per cycle and t is the sampling time;

[0016] Step S14, use the set data acquisition card to collect the stator current signal i(t) of the asynchronous motor;

[0017] Step S15, perform spectral analysis on the collected current signal i(t) to obtain the frequency f1;

[0018] Step S16, calculate the absolute error Δf between f1 and the frequency reference value f r = |f1 - f r |;

[0019] Step S17, determine whether the absolute error Δf is greater than the preset frequency accuracy Δf s , if not, complete the data acquisition; if so, set the f1 obtained in step S15 as the new frequency reference value and enter S12 to collect again.

[0020] (S12~S17 are to set the data acquisition card to perform full-cycle sampling on the stator current signal of the motor to prevent spectral leakage from affecting the extraction of the frequency and amplitude of the harmonic components of the stator inter-turn short-circuit fault)

[0021] Furthermore, the specific process of step S2 is as follows:

[0022] Step S21, perform a frequency shift transformation on the stator current signal i(t) of the asynchronous motor in step S1 to obtain the original stator current signal x(t) of the asynchronous motor, so that the original stator current signal x(t) of the asynchronous motor satisfies the decomposable conditions of empirical mode decomposition; where the decomposable conditions of empirical mode decomposition are f 小 is the frequency of the signal component with a smaller frequency, a 小 is the amplitude corresponding to f 小 f 大 is the frequency of the signal component with a larger frequency, a 大 is the frequency corresponding to f 大 ;

[0023] Step S22, perform empirical mode decomposition on the original asynchronous motor stator current signal x(t) after frequency shift transformation in Step S21; after decomposition, a group of intrinsic mode function components imf i (t) are obtained, and the components are arranged in descending order of frequency.

[0024] Further, the specific process of Step S3 is as follows:

[0025] Step S31, select one intrinsic mode function component imf i from the intrinsic mode function components imf st (t) whose frequency is closest to the theoretical value f re of the stator inter-turn short circuit fault harmonic frequency;

[0026] Step S32, use Hilbert transform to calculate the squared signal of the envelope of imf re (t);

[0027] Step S33, perform spectral analysis on the squared envelope signal in Step S32 to obtain the measured frequency f re and amplitude A re of the stator inter-turn short circuit fault harmonic.

[0028] Further, the specific process of Step S21 is as follows:

[0029] Step S211, extract the current components in the asynchronous motor stator current signal i(t) whose amplitudes are greater than the threshold, and judge whether the components with adjacent frequency values meet the decomposable condition. If all meet, do not process the current signal; if only f 小 / f 大 < 0.5, enter S212; otherwise, enter S213;

[0030] Step S212, extract the phase θ 大 of the signal component with frequency f 大 , construct a signal with frequency f 大 and phase θ 大 , superimpose it on the current signal, and adjust the amplitude of the current component to make the current signal meet the second condition;

[0031] Step S213, perform frequency shift on the motor current so that f is the set moving frequency.

[0032] Further, the specific process of Step S22 is as follows:

[0033] Step S221, let x(t) be the original signal to be processed and t be the time series. Use cubic spline interpolation method to fit the local maximum and local minimum values of the original signal respectively to obtain the upper envelope xmax (t) and the lower envelope x min (t);

[0034] Step S222, calculate the mean of the upper and lower envelopes to obtain the local mean m1(t) of the original signal = [x max (t) - x min (t)] / 2;

[0035] Step S223, subtract the local mean from the original signal to complete one sifting, and denote the intermediate signal as h1(t) = x(t) - m1(t);

[0036] Step S224, determine whether the intermediate signal h1(t) has a negative local maximum or a positive local minimum (that is, determine whether there is a maximum less than 0 and a minimum greater than 0). If so, take h1(t) as the new original signal and return to Step S221; otherwise, the intermediate signal h1(t) is the first intrinsic mode function imf1(t) of the original signal x(t), and enter Step S225;

[0037] Step S225, subtract the intermediate signal h1(t) from the original signal x(t) to obtain the residual signal r1(t) = x(t) - h1(t);

[0038] Step S226, take r1(t) as the new original signal to be processed, return to (1), and repeat Steps S221 - S225 to successively obtain the intermediate signal time series h i (t) as the intrinsic mode function imf i (t), until a monotonic residual signal sequence r num (t) is obtained, and the empirical mode decomposition is completed, obtaining a set of signal components h i (t), num represents the number of intrinsic mode functions, and each component is arranged in descending order of frequency.

[0039] Furthermore, the specific process of Step S32 is as follows:

[0040] Step S321, assume that the time series of the intrinsic mode function containing the fault-induced current component is: imf re (t) = A h cos(2πf h t + θ h ) + A re cos(2πf re t + θ re ), where f h is the power supply harmonic frequency, A h is the amplitude corresponding to f h , θ h is the phase corresponding to f h ), fre is the measured harmonic frequency of the stator turn - to - turn short - circuit fault, A re is f re corresponding amplitude, θ re is f re corresponding phase;

[0041] Perform the Hilbert transform on imf re (t) to obtain

[0042] Step S322, construct the analytic function j is the imaginary unit.

[0043] Step S323, find the squared signal of the envelope of the analytic function:

[0044]

[0045] The technical effect of the present invention is:

[0046] In the stator turn - to - turn short - circuit fault detection method of the asynchronous motor in the present invention, data is first collected using the closed - loop tracking algorithm, which simplifies the hardware circuit. Then, empirical mode decomposition is used for the preliminary extraction of fault characteristic frequencies, avoiding the interference of other types of faults. Next, Hilbert envelope square demodulation is used to further highlight the fault characteristic frequencies and weaken the influence of spectral leakage. Finally, whether the current signal is abnormal is judged by the change of the amplitude of the fault characteristic frequency. When an abnormality occurs, an alarm is sent in time to ensure the safe and reliable operation of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The accompanying drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0048] In the drawings:

[0049] Figure 1 is the flowchart of the working process of a stator turn - to - turn short - circuit fault detection method for an asynchronous motor according to the present invention.

[0050] The symbols appearing in the specification and their corresponding meanings are shown in the following table:

[0051]

[0052]

[0053] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions are only used to explain the present invention, but not to unduly limit the present invention.

[0055] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0056] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0057] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprise" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices.

[0058] For ease of description, spatial relative terms such as "above", "over", "on the upper surface", "above" etc. can be used here to describe the spatial positional relationship of a device or feature shown in the figure with other devices or features. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device shown in the figure. For example, if the device in the figure is inverted, the device described as "above" or "over" other devices or structures will then be positioned "below" or "beneath" other devices or structures. Thus, the exemplary term "above" can include both the orientations of "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and corresponding interpretations will be made for the spatial relative descriptions used here.

[0059] A method for detecting the inter-turn short circuit fault of an asynchronous motor stator includes the following steps:

[0060] Step S1, collect the motor speed to obtain the stator current signal of the asynchronous motor;

[0061] Preferably, the specific process of step S1 is as follows:

[0062] Step S11, collect the speed n1 of the asynchronous motor, calculate the slip ratio s and the theoretical value f of the frequency of the stator turn - to - turn short - circuit fault harmonics st ; where s=(n0 - n1) / n0, n0 is the synchronous speed,

[0063] The formula for calculating the theoretical value of the frequency of the stator turn - to - turn short - circuit fault harmonics of the asynchronous motor is p is the number of pole pairs of the asynchronous motor, s is the slip ratio, f0 is the power supply fundamental frequency, k is a positive integer, and n is the rotor harmonic order;

[0064] Step S12, preset a frequency reference value f0 is the power supply fundamental frequency, n is the rotor harmonic order, p is the number of pole pairs of the asynchronous motor, and k is a positive integer;

[0065] Step S13, set the sampling frequency f of the data acquisition card s =mf r and the number of sampling points N = t×f s , m is the number of sampling points per cycle, and here m takes 20; t is the sampling time.

[0066] Step S14, use the set data acquisition card to collect the stator current signal i(t) of the asynchronous motor;

[0067] Step S15, perform spectral analysis on the collected current signal i(t) to obtain the frequency f1;

[0068] Step S16, calculate the absolute error Δf between f1 and the frequency reference value f r =|f1 - f r |;

[0069] Step S17, determine whether the absolute error Δf is greater than the preset frequency accuracy Δf s , if not, complete the data acquisition; if so, set the f1 obtained in step S15 as the new frequency reference value and enter S12 to re - collect.

[0070] Step S2, screen the stator current signal of the asynchronous motor in step S1 to confirm the original stator current signal of the asynchronous motor;

[0071] Step S21: Perform a frequency shift transformation on the asynchronous motor stator current signal \(i(t)\) in Step S1 to obtain the original asynchronous motor stator current signal \(x(t)\), so that the original asynchronous motor stator current signal \(x(t)\) satisfies the decomposable conditions of empirical mode decomposition; where the decomposable conditions of empirical mode decomposition are f 小 is the frequency of the signal component with a smaller frequency, and \(a\) 小 is the amplitude corresponding to \(f\) 小 ; \(f\) 大 is the frequency of the signal component with a larger frequency, and \(a\) 大 is the amplitude corresponding to \(f\) 大 .

[0072] Step S211: Extract the current components in the asynchronous motor stator current signal \(i(t)\) whose amplitudes are greater than the threshold, and determine whether the components with adjacent frequency values satisfy the decomposable conditions. If all satisfy, do not process the current signal; if only \(f\) 小 / f 大 < 0.5, enter S212; otherwise, enter S213;

[0073] Step S212: Extract the phase \(\theta\) 大 of the signal component with frequency \(f\) 大 , construct a signal with frequency \(f\) 大 and phase \(\theta\) 大 , superimpose it on the current signal, and adjust the amplitude of the current component to make the current signal satisfy the second condition;

[0074] Step S213: Perform a frequency shift on the motor current so that f is the set moving frequency.

[0075] Step S22: Perform empirical mode decomposition on the original asynchronous motor stator current signal \(x(t)\) after the frequency shift transformation in Step S21; After decomposition, a set of intrinsic mode function components \(imf\) i (t) are obtained, and the components are arranged in descending order of frequency.

[0076] The specific process of Step S22 is as follows:

[0077] Step S221: Let \(x(t)\) be the original signal to be processed and \(t\) be the time series. Use the cubic spline interpolation method to fit the local maximum and local minimum values of the original signal respectively to obtain the upper envelope \(x\) max (t) and the lower envelope \(x\) min (t) of the original signal;

[0078] Step S222: Calculate the mean of the upper and lower envelopes to obtain the local mean \(m1(t)=[x\) max (t) - x min (t)] / 2;

[0079] Step S223: Subtract the local mean from the original signal to complete one sifting, and obtain the intermediate signal denoted as: h1(t) = x(t) - m1(t);

[0080] Step S224: Determine whether the intermediate signal h1(t) has a negative local maximum or a positive local minimum (i.e., determine whether there is a maximum value less than 0 and a minimum value greater than 0). If so, take h1(t) as the new original signal and return to Step S221; otherwise, the intermediate signal h1(t) is the first intrinsic mode function imf1(t) of the original signal x(t), and enter Step S225;

[0081] Step S225: Subtract the intermediate signal h1(t) from the original signal x(t) to obtain the residual signal r1(t) = x(t) - h1(t);

[0082] Step S226: Take r1(t) as the new original signal to be processed, return to (1), and repeat Steps S221 - S225 to successively obtain the intermediate signal time series h i (t) as the intrinsic mode function imf i (t), until a monotonic residual signal sequence r num (t) is obtained, and the empirical mode decomposition is completed, obtaining a set of signal components h i (t), num represents the number of intrinsic mode functions, and each component is arranged in descending order of frequency.

[0083] Step S3: Process the original stator current signal of the induction motor obtained in Step S2 to extract the characteristic frequency characterizing the stator inter-turn short circuit fault;

[0084] Preferably, the specific process of Step S3 is as follows:

[0085] Step S31: Select an intrinsic mode function component imf i (t) from the intrinsic mode function components imf st whose frequency is closest to the theoretical value f re of the harmonic frequency of the stator inter-turn short circuit fault;

[0086] Step S32: Calculate the squared signal of the envelope of imf re (t) using the Hilbert transform; the specific process is as follows: Step S321: Let the time series of the intrinsic mode function containing the fault-induced current component be:

[0087] imf re (t) = A h cos(2πf h t + θ h ) + A recos(2πf re t + θ re ), where f h is the power supply harmonic frequency, A h is the amplitude corresponding to f h , θ h is the phase corresponding to f h ; f re is the measured harmonic frequency of the stator inter-turn short circuit fault, A re is the amplitude corresponding to f re , θ re is the phase corresponding to f re ; perform Hilbert transform on imf re (t) to obtain

[0088]

[0089] Step S322, construct the analytic function where j is the imaginary unit.

[0090] Step S323, find the squared signal of the envelope of the analytic function:

[0091]

[0092] Step S33, perform spectral analysis on the squared envelope signal in Step S32 to obtain the measured frequency f re and amplitude A re of the stator inter-turn short circuit fault harmonic.

[0093] Step S4, set the amplitude increment reference value, compare the amplitude changes of the characteristic frequencies extracted in Step S3 to determine whether to issue an alarm or end.

[0094] In summary, as Figure 1 shown, the method for detecting stator inter-turn short circuit fault of an asynchronous motor according to the present invention includes the following steps:

[0095] First, perform calculation and signal full-cycle sampling:

[0096] Collect the rotational speed of the asynchronous motor, calculate the slip ratio s and the fault induced current frequency where p is the number of pole pairs of the motor;

[0097] Select the power supply harmonic frequency f0 closest to the fault induced current frequency f st as the target current signal frequency, and perform full-cycle sampling on the asynchronous motor current signal at a sampling frequency of 20f0 with t as the sampling time;

[0098] Secondly, condition the motor current signal to make it meet the decomposable conditions of empirical mode decomposition:

[0099] The decomposable conditions of empirical mode decomposition are where f 小 is the frequency of the signal component with a smaller frequency, a 小 is the amplitude corresponding to f 小 ; f 大 is the frequency of the signal component with a larger frequency, a 大 is the amplitude corresponding to f 大 .

[0100] a: Extract the frequency, amplitude, and phase of the power supply harmonic component i1(t) whose frequency is close to the fault characteristic frequency f st .

[0101] b: Construct a function based on the extracted frequency, amplitude, and phase of i1(t), and perform frequency shift and amplitude adjustment on the power supply signal component i1(t) so that each signal component satisfies the decomposable conditions of empirical mode decomposition.

[0102] Again, perform empirical mode decomposition on the transformed motor current signal, extract the intrinsic mode function component containing the fault-induced current, and perform inverse transformation to restore it to its original state;

[0103] Again, use Hilbert transform to obtain the envelope square signal of the restored intrinsic mode function component, and perform spectrum analysis to obtain the frequency and amplitude of the fault-induced current, and determine whether the amplitude increase of the fault-induced current is greater than the reference value. If so, issue an alarm;

[0104] Finally, determine whether to continue the detection. If so, collect information again; if not, end.

[0105] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for detecting the inter-turn short circuit fault of the stator of an asynchronous motor, characterized in that, It includes the following steps: Step S1, collect the motor speed and the asynchronous motor stator current signal; Step S2, condition the asynchronous motor stator current signal in Step S1 to confirm the original asynchronous motor stator current signal; Step S3, process the original asynchronous motor stator current signal obtained in Step S2 to extract the frequency and amplitude of the stator inter-turn short circuit fault harmonic components; Step S4, set the amplitude increment reference value, compare the amplitude change of the characteristic frequency extracted in Step S3 to determine whether to issue an alarm or end; The specific process of Step S1 is as follows: Step S11, collect the rotational speed of the asynchronous motor , calculate the slip ratio s and the theoretical value of the frequency of the stator inter-turn short-circuit fault harmonics ; Among them, , is the synchronous speed, The theoretical value calculation formula for the frequency of the harmonics of the inter-turn short circuit fault in the stator of an asynchronous motor is , where p is the number of pole pairs of the asynchronous motor, is the slip ratio, is the fundamental frequency of the power supply, is a positive integer, is the rotor harmonic order; Step S12, preset a frequency reference value ; is the fundamental frequency of the power supply, is the rotor harmonic order, p is the number of pole pairs of the asynchronous motor, is a positive integer; Step S13, set the sampling frequency of the data acquisition card and the number of sampling points , is the number of sampling points per cycle, is the sampling time; Step S14, collect the stator current signal of the asynchronous motor by using the set data acquisition card ; Step S15, perform spectral analysis on the collected current signal to obtain the frequency ; Step S16, calculate and the frequency reference value for the absolute error ; Step S17, determine the absolute error is greater than the preset frequency accuracy , if not, complete the data acquisition; if so, set the obtained in step S15 as the new frequency reference value, and enter S12 to re-collect; The specific process of Step S2 is as follows: Step S21, for the asynchronous motor stator current signal in Step S1 perform frequency shift transformation to obtain the original asynchronous motor stator current signal , so that the original asynchronous motor stator current signal meets the decomposable conditions of empirical mode decomposition; among them, the decomposable conditions of empirical mode decomposition are , is the frequency of the signal component with a smaller frequency, is the amplitude corresponding to the frequency of the signal component with a smaller frequency, is the frequency of the signal component with a larger frequency, is the amplitude corresponding to the frequency of the signal component with a larger frequency; Step S22: Perform empirical mode decomposition on the original asynchronous motor stator current signal after frequency shift transformation in Step S21 After decomposition, a set of intrinsic mode function components is obtained and the components are arranged in descending order of frequency The specific process of Step S3 is as follows: Step S31, select an intrinsic mode function component from the intrinsic mode function components whose frequency is closest to the theoretical value of the harmonic frequency of the stator inter-turn short circuit fault ; Step S32, calculate using Hilbert transform the squared signal of the envelope; Step S33: Perform spectral analysis on the enveloped square signal in step S32 to obtain the measured frequency of the stator inter-turn short circuit fault harmonics and amplitude ; The specific process of Step S21 is as follows: Step S211: Extract the stator current signal of the asynchronous motor Extract the current components with amplitudes greater than the threshold in and determine whether the components with adjacent frequency values meet the decomposable conditions. If all meet, do not process the current signal; if only meets, enter S212; otherwise, enter S213; Step S212, extract the frequency The phase of the signal component , constructed with a frequency of , the phase is The signal is superimposed on the current signal, and the amplitude of the current component is adjusted so that the current signal meets the second condition; Step S213, shift the frequency of the motor current so that ; is the set moving frequency.

2. The asynchronous motor stator turn-to-turn short circuit fault detection method according to claim 1, characterized in that, The specific process of Step S22 is as follows: Step S221, set as the original signal to be processed, t as the time series, and use the cubic spline interpolation method to fit the local maxima and local minima of the original signal respectively to obtain the upper envelope and the lower envelope ; Step S222: Calculate the mean value of the upper and lower envelope lines to obtain the local mean value of the original signal ; Step S223, subtract the local mean from the original signal to complete one sifting, and denote the resulting intermediate signal as ; Step S224, determine whether the intermediate signal has a negative local maximum or a positive local minimum. If so, take as the new original signal and return to step S221; otherwise, the intermediate signal is the first intrinsic mode function of the original signal , and proceed to step S225; Step S225, subtract the intermediate signal from the original signal to obtain the residual signal ; Step S226, take as the new original signal to be processed, return to (1), and repeat Steps S221 to S225 to obtain the intermediate signal time series as the intrinsic mode function , until the monotonic residue signal sequence is obtained, and the empirical mode decomposition is completed to obtain a set of signal components , where num represents the number of intrinsic mode functions, and each component is arranged in the order of decreasing frequency.

3. The asynchronous motor stator inter-turn short circuit fault detection method according to claim 2, characterized in that, The specific process of Step S32 is as follows: Step S321, set the time series of the intrinsic mode function containing the fault-induced current component as: , where is the power supply harmonic frequency, is the corresponding amplitude, is the corresponding phase, is the measured harmonic frequency of the stator inter-turn short circuit fault, is the corresponding amplitude, is the corresponding phase; Perform a Hilbert transform to obtain ; Step S322, construct an analytical function ; is the imaginary unit; Step S323, obtain the square signal of the envelope of the analytical function: .

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