Analysis of double‐sided sandwiched linear flux‐switching permanent‐magnet machines with staggered stator teeth for urban rail transit

Abstract

Linear flux-switching permanent-magnet (LFSPM) machines exhibit significant potential in many applications. A double-sided sandwiched LFSPM (DSSLFSPM) machine with high thrust force capability is investigated in this study. After being optimised for optimal thrust force using Maxwell 2D, this machine is found to deliver higher thrust force when compared with an optimised conventional 12/14 LFSPM machine. However, low thrust force ripple is also required in many applications. Thus, in order to reduce the thrust force ripple, the DSSLFSPM machine is improved by a staggered stator teeth structure and an end permanent-magnets method, then, two improved machines are obtained. The improved machines can reduce the thrust ripple to a very low level without thrust force density decrease. Further, the stator yoke thickness of the improved machines is optimised to reach optimal thrust force density. Finally, the performance of the DSSLFSPM-ST machines is analysed including the normal force, the efficiency and the power factor. It shows that the improved DSSLFSPM machines exhibit relatively low normal force and high thrust force density as well as low thrust ripples, indicating that they are suitable for long-stroke applications.