This paper compares two flux-switching machines, namely, one stator permanent magnet flux-switching machine and one rotor permanent magnet flux-switching (RPM-FS) machine, with the same overall dimensions, main material properties, and current density. The comparison of characteristics is conducted from two perspectives, i.e., the electromagnetic torque production mechanism and torque (power)-sizing equation. The contribution of harmonics to average electromagnetic torque is analyzed based on the modulation principle and gearing effect, which reflects the similarities and differences between two FS machines in torque production mechanism. Moreover, torque performances are investigated from the viewpoints of magnetic parameters and electrical parameters. Then, electromagnetic performances including overload capability, flux-weakening capacity, and efficiency are analyzed and compared further. The predicted results indicate the RPM-FS machine exhibits a larger torque capability, a lower torque ripple, and improved flux-weakening capacity. The finite-element analysis predicted results are validated by experiments on two prototype machines.

Flux switching permanent magnet machine exhibits high cogging torque due to the doubly salient topology and high air gap flux density. This paper proposes a new axial-modular flux switching permanent magnet (AM-FSPM) machine, which has an improved torque capability and the potential of cogging torque suppression by module combination technique. The cogging torque analytical expression of the machine with axial-modular topology is derived based on a magnetomotive force-permeance model. Then, the AM-FSPM machines are divided into two types by the combinations of stator-slot and rotor-pole, named fundamental harmonic offset naturally and fundamental harmonic offset manually. In addition, four approaches are investigated to reduce cogging torque by changing modular magnetomotive force and changing modular permeance. It can be concluded that the modular rotor tooth combination method has the most attractive torque performances among the four methods. Finally, the effectiveness of the proposed approaches is verified by the 3D finite element analysis and experimental results.

This paper proposes a novel axial-modular-flux switching permanent magnet (AM-FSPM) machine, which contains two modular parts and integrated toroidal windings. After investigating the operation principle of the AM-FSPM machine, the modular PM field complementarity and integrated armature reaction field complementarity principles of two axial modular parts are revealed based on the field modulation theory. Then, a comprehensive comparison of the modulation principle between the AM-FSPM and conventional FSPM machines is conducted from perspectives of PM field, armature reaction field, cogging torque and electromagnetic torque production mechanism. It can be found that the modulation principle reveals the difference between the operation principles of two flux switching machines. In addition, the cogging torque reduction capability of AM-FSPM machine is investigated, which provides guidance on stator-slot and rotor-pole combinations in the design stage of industrial applications. Moreover, compared with conventional FSPM machines, the AM-FSPM machine exhibits high torque capability and flux weakening capability, meanwhile maintains high efficiency at high speed. Further, its characteristics are verified by the experiments.