Operation Mechanism and Characteristics Evaluation of Axial Flux Reversal Permanent Magnet Machine with Different Magnetization Methods

In this paper, a novel axial flux reversal permanent magnet (PM) (AFRPM) machine with different magnetization methods including “NS-SN” (called m1) and “NS-NS” (called m2), which inherits the characteristics of the axial flux PM (AFPM) machine and the flux reversal principle, is designed and investigated. Firstly, the topology and operating principle are analyzed and the structure parameters are obtained. In order to make a fair comparative analysis, the geometric parameters of the AFRPM machine with two magnetization methods are identical. Secondly, the PM magnetomotive force (MMF), rotor permeance and armature reaction MMF models are established and the airgap field modulation principle of the machine with m1 and m2 is researched. Then, the contribution of the harmonic components to the electromagnetic torque is analyzed and summarized, which reveals the difference of torque generation mechanism in the AFRPM machine with m1 and m2. Meanwhile, the machine with m2 exhibits a larger torque. Moreover, the electromagnetic performance of the machine with m1 and m2, including PM flux-linkage, back electromotive force (EMF), torque characteristics and so on, is investigated comparatively. The global multi-objective optimization based on the genetic algorithm is implemented to improve the performance of the machine with m2. Finally, a prototype machine is fabricated to validate the finite element analysis. The results show that the performance of the machine with m1 and m2 is excellent. Moreover, the machine with m2 has larger back-EMF with higher quality, superior torque capability and higher power density, which is identified with the theoretical analysis.