Current similarity based fault diagnosis for induction motor drives with discrete wavelet transform

Three-phase voltage-source inverters (VSI) fed induction motor (IM) with space-vector controlled scheme are widely used in industrial applications. The suffered failures will degrade the system performance with output torque ripple and harmonic currents. In this paper, a new diagnosis method is proposed to detect and locate the insulated gate bipolar translator (IGBT) open-circuit fault. Discrete wavelet transform (DWT) is used as a pre-treatment technique for three-phase output currents, the approximate coefficients are applied to obtain energy vectors. Correlation coefficients between every two of the energy vectors are calculated for measuring the current similarity to diagnose fault. When IGBTs occur open-circuit fault, the values of correlation coefficients will be smaller than that under normal conditions, then faults can be detected. Faults can also be located according to the relationship between cumulative correlation coefficients and the legs. Simulation results show high efficiency and merits of the proposed method.