Analytical Design and Optimization of Surface-Mounted PMSMs with Equal-Thickness Air Gap

This paper proposes a method of analytical design and optimization for surface-mounted permanent magnet synchronous motor (SPMSMs) with equal-thickness air gap, which has better assembly accuracy and lower electrode inter-pole leakage. The outer surface of the permanent magnet (PM) is maintained as an arc shape, and the internal surface of the PM is designed and optimized to produce the sinusoidal air-gap flux density, which can reduce torque ripple. The thickness of the PM is derived considering the distortion of the air gap magnetic field by stator slots. In order to improve the average torque and reduce the torque ripple, the thickness of the PMs is further optimized by multiple harmonic injection using a genetic algorithm. Finally, the performance of three SPMSMs, namely, sinusoidal shape, shape considering stator slots, and shape by optimization, are compared.