Research On Fault Diagnosis Method Of Broken Rotor Bar Of Induction Motor Based On Cyclic Spectrum Correlation Analysis

Induction motors are widely used in industrial manufacturing and power conversion fields because of their reliable design,low manufacturing costs,and high applicability.As an important part of the induction motor,the rotor will cause huge economic losses and even endanger personal safety if it appears broken rotor bar fault.In recent years,although various signal processing methods applied to broken rotor bar fault diagnosis of induction motors have achieved good results,they still have the disadvantages of high computational costs and low diagnostic accuracy.Therefore,the diagnosis of broken rotor bar faults is still an extremely demanding task.At the same time,the current popular cyclic spectrum correlation analysis methods have the defects of limited fault modulation frequency analysis range and poor carrier frequency resolution.Based on the shortcomings mentioned above,this paper proposes two optimized measures of the cyclic modulation spectrum method based on cyclic spectrum correlation theory and broken rotor bar failure of induction motors,which provide reliable broken rotor bar damage diagnosis from the modulation frequency and the carrier frequency domains,and improves the defects of cyclic spectrum correlation analysis methods.The specific research content is as follows:(1)The main structure of the induction motor is studied,the main reasons and vibration mechanism of the broken rotor bar failure are analyzed,and a simulation model of the broken rotor bar fault is established.And establish the test rig of broken rotor bar fault of induction motor,then collect vibration response signals of induction motor with different levels of failure under different operating conditions,and perform simple analysis in time and frequency domains to verify the traditional Fourier transform cannot effectively process and analyze complex signals with faulty modulation.(2)Propose the first reasonable application of the CMS algorithm.Short time Fourier transform(STFT)is the core step of CMS.This article will further improve the detection accuracy and decrease the computing costs of CMS applied to broken rotor bar fault diagnosis by optimizing the window function,window length and step size in STFT.The window function,window length,and step size are determined according to the broken rotor bar signal form and calculation efficiency,respectively.Experiments have shown that,for the specific broken rotor bar signal form,the Kaiser(β = 3)window function can greatly improve the diagnostic accuracy of the CMS method.Then,determining the appropriate window length and step size based on the selected window function can further reduce computational load of CMS for broken rotor bar fault diagnosis.(3)Based on the continuous wavelet transform(CWT),the second improved CMS algorithm is proposed to make up for the shortcomings of traditional CMS and fast spectral correlation(FSC)methods due to the use of STFT.The theory and simulation demonstrate that the improved CMS method can expand the modulation frequency analysis range to Fs/2(Fs is the sampling frequency)and improve the resolution of the carrier frequency.In addition,experimental analysis shows that the improved CMS method based on CWT can accurately extract the broken rotor bar fault feature,and the obtained vibration spectrum has no harmonic components or interference components that affect the fault characteristics.Meantime,the method can effectively extract the carrier frequency band modulated by the broken rotor bar fault frequency.The carrier frequency analysis method also provides an effective broken rotor bar failure diagnosis of induction motor from the perspective of carrier frequency.