Fault Detection and Diagnosis of Induction Motors Based on Higher-Order Spectrum

The number of research studies have shown that the fault in the stator or rotor generally show sideband frequencies around the mains frequency (50Hz) and it higher harmonics in the spectrum of the Motor Current Signature Analysis (MCSA). However in the present experimental studies such observations have not seen, but any fault either in the stator or the rotor may distort the sinusoidal response of the motor RPM and the main frequency so the MCSA response may contain number of harmonics of the motor RPM and the mains frequency. Hence the use of the higher order spectrum (HOS), namely the bisepctrum of the MCSA has been proposed here. Additionally, the bispectra with the unwrapped phase angle along its frequency has been applied to analyze motor faults. Thus, this paper proposes bispectrum relates both amplitude and phase of a signal. It has been observed that it not only detects the early fault but also indicate the severity of the fault to some extent.