A novel method for induction motors stator interturn short circuit fault diagnosis by wavelet packet analysis

In this paper, a novel method for stator interturn short circuit fault diagnosis in induction motors using the wavelet packet analysis is presented. Wavelet packet analysis is the extension of wavelet analysis and decompose signal into the equal bandwidth, it can achieve better decomposition result than wavelet analysis does. In the operating induction motor, electromagnetic torque is sensitive to the asymmetry due to the fault. Research indicate that the interturn short circuit fault will give rise to the sidebands at some given harmonic components of the electromagnetic torque signal and some certain frequency components change evidently, the distribution of the energy in the certain frequency bands alter as well. In the proposed method, electromagnetic torque signal is analyzed via wavelet packet decomposition and the wavelet packet coefficients are extracted. Based on each coefficient´s energy eigenvalue, an eigenvector is set up. The presence of the short circuit fault makes the eigenvector change by a special rule, and the fluctuation of the load or supply unbalance make it change in another way, so it is immune to the variety of load and supply. Experimental results demonstrate the validity and effectiveness of this method.