Comparison of flux weakening capability in alternative switched flux permanent magnet machines by mechanical adjusters

To extend the speed range in the switched flux permanent magnet (SFPM) machines, mechanically movable flux adjusters (FAs), which consist of iron pieces located outside the stator, are utilized to adjust the airgap flux density. A comparative study of conventional SFPM machines with different stator/rotor pole combinations, i.e. 12/10, 12/13 and 12/14, and the multi-tooth, E-core, and C-core SFPM machines, is presented with the objective of exploring the best machine topology to equip with the FAs. 2D finite element analysis (FEA) is employed to predict the electromagnetic performance of SFPM machines with emphasis on the flux-weakening capability. Compared with multi-tooth, E-core and C-core types of SFPM machines, the maximum speed can be significantly increased if the conventional SFPM machines are equipped with FAs. Moreover, the 12/13 and 12/14 SFPM machines with FAs may exhibit infinite speed range.