Cogging Torque Reduction of Axial-Field Flux-Switching Permanent Magnet Machine by Rotor Tooth Notching

Axial-field flux-switching permanent magnet machine (AFFSPMM) is a novel PM machine with high power density and efficiency. However, the cogging torque in AFFSPMM is larger than that in the traditional PM machine because of the double salient structure. In order to reduce the cogging torque, the cogging torque reduction method by rotor tooth notching is investigated in this paper. Three different tooth-notching structures are proposed, and the influence of the dummy slot width, slot depth, and slot shape angle on the cogging torque is analyzed based on the 3-D finite-element method (FEM). The optimized tooth-notching structure with the minimum cogging torque is obtained by the response surface method and verified by an FEM. The results show that the cogging torque can be reduced greatly, while the output torque decreases slightly by rotor tooth notching in AFFSPMM. The cogging torque reduction effect by adding two dummy slots in the rotor pole is better than that by adding one dummy slot.