Comparison of Complementary and Modular Linear Flux-Switching Motors With Different Mover and Stator Pole Pitch

Linear flux-switching permanent magnet (LFSPM) motors with both permanent magnets and armature windings on the short primary mover have attracted considerable attention due to their simple and cheap stator which only consists of iron. Hence, this kind of liner motor is very suitable for long stator applications such as in urban rail transportations. However, the conventional LFSPM motors directly split from rotary FSPM motor suffer from drawbacks such as unbalanced magnetic circuit of end coil, heavy mover, and bigger cogging force and force ripple. Modular LFSPM (MLFSPM) motors can mitigate the problem of unbalanced magnetic circuit of end coil. But some MLFSPM motors with different stator/mover pole pitch τ_s/τ_m=12/14, 12/10 don´t have complementary phase armature windings, which will lead to asymmetrical and non-sinusoidal back-electromotive force, bigger cogging force and thrust force ripple. The key of this paper is to propose, investigate, and compare four complementary and modular structures for the LFSPM motors with different τ_s/τ_m . The electromagnetic performance and dimensions of the proposed complementary MLFSPM motors with different τ_s/τ_m are investigated, compared and confirmed by the means of finite element analysis and experimental results. Based on the analysis results, two complementary MLFSPM motors with τ_s/τ_m=12/13 are chosen to be the two best motors, which can offer the biggest thrust force, relatively smaller cogging force and thrust force ripple, and shorter mover length.