A New Perspective on the Operating Principle of Flux-Switching Permanent-Magnet Machines

The flux-switching permanent-magnet (FSPM) machine attracts increasing attention recently due to its high power density, robust mechanical structure, good flux-weakening capability, and essential sinusoidal back-electromotive-force waveforms. In previous studies, the approach for analyzing FSPM machines is either by using the lumped parameter magnetic circuit models or from the 'generator-oriented' perspective. In this paper, the operating principle of FSPM machines is reiterated from a new perspective, viz., the 'motor-oriented' perspective. Some interesting findings and essential principles can be unveiled, which include how the stable electromagnetic torque can be developed, how the pole-pair number (PPN) of armature windings, the PPN of PMs, and the synchronous speed of the armature field should be defined, and how to determine the connection of coils for the sake of developing stable electromagnetic torques. This new perspective is more consistent with the classical theory on electric machines. There is no need to consider the polarity of coils when determining the connection of windings. Three typical FSPM machines with different combinations of stator and rotor poles, viz., 12/11-pole, 12/13-pole, and 12/26-pole, are investigated to verify the validity of the proposed analysis approach. Experimental verification concerning the latter two sample machines is also conducted.