Research On Rotor Fault And Severity Diagnosis Of Squirrel-cage Induction Motor

In the application of industry,faults may be occurred under the condition that the squirrel-cage motor is frequently started and braked or under uninterrupted operation.The occurrence of the faults may cause the fluctuation of whole system and may trigger greater system faults,which not only affect the normal production and in severe cases can lead to huge economic losses or endanger personal safety.Therefore,research on motor fault diagnosis is very important.The traditional MCSA methods are used to analyze the steadystate current,which can effectively diagnose the fault,but these methods have some certain limitations.On one hand,these techniques are lack of efficiency and even can not give the accurate identification of the fault,because the amplitude of feature component is much smaller than the power fundamental component and it may be covered by the fundamental component in frequency domain owing to the truth that its frequency is close to the fundamental frequency.On the other hand,these traditional methods can't detect the severity of rotor.This paper is focused on the analysis of motor start-up transient current,and different signal processing methods combining curve-fitting method is presented for the diagnosis of rotor asymmetry fault and severity detecting.The contributions are as follows:1.The theory of several signal processing methods such as time–frequency methods,Fr FT are analyzed,and simulated data and steady-state fault data of a motor are used to validate the accuracy of the algorithms.2.Model of squirrel-cage motor and rotor asymmetry fault are established by Ansoft Maxwell,and WT is used to extract the transient feature signal.Then,some methods such as STFT,EMD,WT,SWT,Fr FT are used to analyze the feature signal.3.A method to diagnose the rotor asymmetry fault severity based on curve-fitting is proposed in this paper.Firstly,WT is applied to detect the rotor asymmetry fault.Then,an index for fault severity is presented,and fault thresholds are calculated by simulation experiment,which can give the evaluation of rotor asymmetry fault severity.Finally,simulation experiments show that the method mentioned above is effective to diagnose rotor asymmetry fault severity.