Validation of a new method for the diagnosis of rotor bar failures via wavelet transformation in industrial induction machines

In previous works, the authors proposed a novel method for the diagnosis of rotor bar failures in induction machines, based on the analysis of the startup stator current through the discrete wavelet transform (DWT). In those works the physical basis of the method was described and several verifications were done in order to confirm its validity. These verifications were satisfactory, but they were based on numerical simulations and on several tests that were developed using a laboratory machine, with certain particular constructive characteristics, different from those of the commercial motors. In the paper to be presented, the validity of the new diagnosis method is checked using a set of commercial induction motors. Several experiments are developed under different cases (healthy machine and machine with different levels of failure) and operating conditions (no load, full-load, pulsating load and fluctuating voltage). In each case, the results are compared with those obtained using the classical approach, based on the analysis of the steady-state current using the Fourier transform. Finally, the results are discussed and some considerations about the influence of the DWT parameters (type of mother wavelet, order of the mother wavelet, sampling rate or number of levels of the decomposition) over the diagnosis are done.