Demagnetization assessment of 6-phase fractional-slot permanent magnet machines with low space harmonics under various fault conditions

The 6-phase fractional-slot per pole, per phase Interior Permanent Magnet (IPM) machine designed for a segment-A electric vehicle (EV) having a novel topology of 18-slot, 8-pole is assessed for the risk of partial irreversible demagnetization under various fault conditions. The paper describes the approach of demagnetization assessment using 2-D transient finite element analysis (FEA) for short circuit faults at the base speed and at the maximum cruise speed with rated and maximum load operation. The flux density of each node in each permanent magnet (PM) is decomposed in the magnetizing direction for a comprehensive assessment. The risk of demagnetization during the transient is evaluated, and the demagnetization levels in different PM poles under short circuit faults at different speeds are highlighted.