Double frequency sliding and wavelet analysis for rotor fault diagnosis in induction motors under time-varying operating condition

The detection of rotor faults in squirrel cage motors has long been an important but difficult matter in the area of electrical machine diagnosis. Under time-varying condition, the typical rotor fault frequency components (RFFCs), which appear in the phase current spectrum of faulted motors, are spread in a bandwidth proportional to the speed variation and are difficult to detect accurately. Thereby a new diagnosis method based on the combined use of bi-frequency sliding (BFS) and discrete wavelet transform (DWT) is proposed here for stator phase current analysis. Simulation and experimental results are reported to validate the effectiveness of the proposed approach under critical speed varying conditions.