Normal Force Reduction Strategy on Linear Flux-Switching Permanent Magnet Motor for Rail Transit

Linear flux-switching permanent magnet motors (LFSPMs) are suitable for long stator applications, such as rail transit, due to their simple and cost-effective stator structure. However, they typically exhibit a significantly higher normal force than thrust, which increases wheel-rail wear. It is nearly impossible to simultaneously reduce the normal force and increase the thrust, as these are electromagnetic forces acting in different directions. Therefore, a normal force reduction strategy for LFSPMs is proposed in this paper, which provides references for designing LFSPMs for rail transit. First, sensitivity analysis of the geometric parameters in the LFSPM is accomplished by analytical calculations and finite element algorithm (FEA). Second, global optimization of the selected parameters is performed by combining FEA with an optimization algorithm to reduce the normal force while maintaining enough thrust and power factor. Third, the optimized LFSPM structure is further modified for mechanical installation, and a small-sized prototype is constructed. Finally, the optimization strategy is validated through the comparison between FEA, analytical calculations, and experimental results of the designed LFSPM.