Detection of Bearing Faults in Cage Induction Motors Fed by Frequency Converter using Spectral Analysis of Line Current

Detection of faults in cage induction motors based on spectral analysis of line current is a well-known technique in the case of sinusoidal supply. Nevertheless, nowadays there are a huge number of applications for the induction motor fed by frequency converter and, therefore, it is necessary to validate, or even modify, the existing fault detection methods, in order to use reliable and effective techniques. In this paper, first we approach, from a theoretical point of view, the effect of bearing faults on the harmonic frequencies of line current, taking into account the presence of numerous harmonics, not related to the fault, injected into the current by the converters themselves. As a result, we propose a novel formulation for the calculation of fault frequencies, suitable for any kind of supply. Finally, this innovative formulation is experimentally verified with tests of traction motor drives, and some conclusions and guidance for the early detection of these kinds of faults are provided, modifying and enriching the methods currently used