Modulation signal bispectrum analysis of motor current signals for stator fault diagnosis

Induction motors are the most widely used electrical machines in industry. To diagnose any possible incipient faults, many techniques have been developed. Motor current signature analysis (MCSA) is a common practice in industry to find motor faults. However, because small modulations due to faults it is difficult to quantify it in the measured signals which predominates with supply frequency, higher order harmonics and noise. In this paper a modulation signal (MS) bispectrum is investigated to detect different severities of stator faults. It shows that MS bispectrum has the capability to accurately estimate modulation degrees and suppress the random and nonmodulation components. Test results show that MS bispectrum has a better performance in differentiating spectrum amplitudes due to stator faults and hence produces better diagnosis performance, compared with that of conventional power spectrum analysis.