Irreversible demagnetization diagnosis of IPM-type BLDC motor using BEMF harmonic characteristics based on space harmonics

In this paper, we analyze the back electromotive force (BEMF) characteristics according to the magnetization pattern of irreversible demagnetization to determine the fault type for interior permanent-magnet (IPM) type brushless DC (BLDC) motors. We numerically model irreversible demagnetized PMs using space-harmonics analysis. In addition, we analyze the results using the finite element and analytical methods. Demagnetization can be predicted by performing mathematical analyses using space harmonics. We then experimentally verify the harmonic characteristics of a test motor. Finally, we propose an irreversible demagnetization diagnosis technique for IPM-type BLDC motors using the harmonic characteristics of the BEMF.