Research And Design On Online System Failure Diagnosis Of Asynchronous Motor

Motor is the most important motive power and drive in modern industrial production and daily life.When electric machinery is in fault,power cut will happen in some places so that there is huge economy loss and important influence on society.So the study on the fault diagnosis theory and technology of electric machinery under all kinds of instance is a pledge,which makes equipments work normally.As the fault signals of electric machine are non-stationary transient ones,the traditional signal analysis methods,such as Fourier Transform,are not efficient enough or useful for the fault signal extraction.However,wavelet analysis and wavelet packet analysis have the excellent time-frequency local performance,it can detect the different frequency components of the fault signals by its adjustable time-frequency window.Considering the superiority of wavelet packet analysis to non-stationary signals,this paper focuses on how to analyze and extract the fault signals by wavelet packet analysis.Based on the works previously,the type of the fault and the method of diagnosis in induction motors were summarized。Then a discussion was made on the fault causes of the motor bearing abnormal,rotor bar breaking,airgap eccentricity and so on.At last,adopting vibration diagnosis and current monitoring method,bearing fault and broken bars fault were diagnosed.In order to simulate true fault,the fault of the motor bearing was made by man.At first,author made use of kurtosis index to judge a bearing is in normal or not,then vibration signals were decomposed by db3 wavelet packet at sixth levels,and then the frequency band signals containing characteristic frequencies were reconstructed by the wavelet packet,thus bearing fault characteristic frequencies were obtained.According to its value and energy, the type of the bearing fault could be confirmed accurately.Meanwhile,method of wavelet packets and FFT to detect the broken bars fault signal of motor were put forward,it was proved that bearing fault and broken bars fault of asynchronous motor could be accurately detected by using these methods.In this paper,the author have designed the main hardware circuit of the induction motor fault diagnosis system based on DSP,including signal detection circuit,signal processing circuit,communication module and so on.The main flowchart of software was given finally.