Five‐phase modular stator surface‐mounted permanent magnet machine with reduced space sub‐harmonics

Multiphase modular stator surface‐mounted permanent magnet machines (MSPMs) feature short end connection, unity winding factor, and low cost. However, they also exhibit rich space harmonics. A five‐phase MSPM with reduced space sub‐harmonics is proposed in this paper. The phase‐shifting method and magnetic flux barriers are adopted to reduce the slot harmonic and lowest order harmonic, respectively. A modified MSPM used for phase shifting is specially proposed. Further, the phase‐shifted MSPMs without and with magnetic flux barriers are both studied to show the separate effectiveness of the phase‐shifting method and magnetic flux barriers. The phase‐shifting angle is determined based on winding function method and the optimal angle is fixed considering the minimal tooth width. A double‐layer MSPM with 20 slots and 22 poles is exemplified, and two single‐layer 40‐slot 22‐pole MSPMs, which are respectively equipped without and with magnetic flux barriers, are proposed. Finite element analysis is performed, and the comparison results show that the space sub‐harmonics, permanent magnet eddy current loss, and the lowest mode of vibration are largely reduced in the phase‐shifted MSPM with magnetic flux barriers. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.