Diagnosis of Broken Rotor Bar Fault of Induction Motor through Envelope Analysis of Motor Startup Current using Hilbert and Wavelet Transform

This paper proposes a new method for extraction of low frequency oscillation from the envelope analysis of Motor Startup Current for diagnosis of Broken Rotor Bar Fault of Induction motor through Wavelet and Hilbert Transforms. The Envelope is the modulus of the Complex Analytic signal generated by using the original signal as the real part and its Hilbert Transform as the imaginary part. The concept of instantaneous frequency introduced in this paper is quite efficient to extract important transient fault informations, specially for non- stationary signal which is nonlinear. This method overcomes the difficulties of traditional FFT and Prony analysis as well as difficulties in selection of mother wavelet. Higher level detail coefficients correspond to narrow band low frequency components below the supply frequency are used to distinguish the faulty motor from the healthy one. Simultaneously this method has higher detectability and higher resolution and it can also deal with short data effectively, so it can be used online. This method has been validated in a laboratory standard