A Review on Poles Demagnetization in Permanent Magnet Motors

Permanent magnet motors like BLDC and PMSM are widely used in industry and electric vehicles. Demagnetization of permanent poles in motors is the biggest problem. To design a machine that has good efficiency and no demagnetization problems, realtime fault diagnosis is necessary. Various causes of demagnetization, detection, and measuring methods are discussed by researchers analyzed in this paper. Apart from the comparison of different methods of fault detection, a general comparison among the different methods of various strategies has been made based on the torque ripple, analysis of harmonics, current waveform, back e.m.f. waveform and losses of the PM motor. Finite Element Analysis (FEA) and analytical method adopted by some researchers to get the results. Moreover, considering the importance of BLDC in the electric vehicles (EVs) industry, the selection of the best method to detect demagnetization has been discussed.