Diagnosis of induction machines under varying speed operation by Principal Slot Harmonic tracking

A detailed study of a Principal Slot Harmonic (PSH) energy of an induction motor directly connected to the grid and operating under variable load under different faulty conditions is carried out. Broken rotor bars, mixed eccentricity and interturn short circuit faults are considered in the paper. A combined time-frequency distribution and particle filtering post processing approach is used in the work for PSH tracking even for the case of severe pulsating load operation. The proposed fault indicator provides values that are comparable with the traditional one for stationary operation. The results show that the energy in the PSH reflects the overall state of the machine under this kind of operation. Furthermore, its changing pattern is studied as a mean to discriminate between different faults.