Thrust Force Enhancement and Ripple Reduction of a Sandwiched Linear Flux Switching Permanent Magnet Machine with Segment Stator for Urban Rail Transit

Linear flux-switching permanent magnet (LFSPM) machines have significant potential in many applications like urban rail transit, automobile and naval. In order to reach high thrust force capability, a sandwiched LFSPM machine (SLFSPM) is investigated in this paper to enhance the usage of both PMs and steel. This machine is found to have higher thrust force after being optimized for maximum thrust force and compared with a optimized conventional 12/14 LFSPM machine based on FEA. However, big thrust ripples will limit its application in many areas. Thus, the SLFSPM machine is improved with two end PMs to suppress the thrust ripple that caused by the unbalanced back-EMFs, and then, to reduce the thrust ripples that caused by cogging force, the SLFSPM machine with segment stator struture (SLFPM-SS) is proposed, and the cogging force can be minimized without thrust force capability decrease. Based on FEA results, the SLFPM-SS machine can maintain high thrust force capability and at the same time, achieve small thrust force ripples and high sinusoidal back-EMFs. (C) 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.