Effects of magnet shape on torque characteristics of Interior Permanent Magnet machines

Interior Permanent Magnet (IPM) motors are widely used in various industrial applications due to many advantages such as high power density, high efficiency, low manufacturing cost and wide constant power operating range. Compared to Surface Mounted Permanent Magnet (SMPM) motors, IPM motors take advantage of both magnetic torque produced by permanent magnets and reluctance torque, which is due to unequal reluctance of the d and q axis. In this paper, the effects of permanent magnet configurations on motor performance are investigated. Three-phase, 8-pole, 9-slot modular and three-phase 4-pole, 36-slot conventional IPM machines have been considered in this study. The effect of straight-shape, V-shape and U-shape permanent magnets on machine performance characteristics are compared through finite element analysis (FEA). The average torque, torque ripple, phase back-EMFs along with constant power operating capability are analyzed.