Transient Analysis of Irreversible Demagnetization of Permanent-Magnet Brushless DC Motor With Interturn Fault Under the Operating State

We investigated the irreversible demagnetization of a permanent-magnet (PM) brushless dc motor under an interturn fault condition. For the transient analysis, we developed a finite-element method-based demagnetization algorithm in the operating state, taking into account the circulating current flowing in the shorted turns and the freewheeling current flowing in the diode. We analyzed the magnetic distribution property, input current, circulating current, and demagnetization characteristic of the PM using this algorithm. The analysis results from the demagnetization algorithm were verified by dynamic fault experiments.