Cogging Torque Reduction of Axial Field Flux-Switching Permanent Magnet Machine by Adding Magnetic Bridge in Stator Tooth

Axial field flux-switching permanent magnet machine (AFFSPMM) is a novel stator PM machine with high torque density and efficiency. The cogging torque in AFFSPMM is larger than that in the traditional PM machine because of the double salient structure. In order to decrease the cogging torque, the analytical expression of the cogging torque is deduced and a cogging torque reduction method by adding magnetic bridge in adjacent stator tooth is proposed. Based on the 3-D finite-element (FE) method, the influence of the magnetic bridge thickness on the cogging torque and the output torque is analyzed and compared with the rotor skewing and notching methods. The influence of the stator tooth and rotor pole width on the output torque is studied. The 3-D FE analysis is compared with the experimental results. The research results show that the proposed method is effective in the reduction of cogging torque for all kinds of stator structures. Moreover, the cogging torque can decrease greatly and the average output torque decreases slightly when combined with the optimization of the stator tooth width and rotor pole width.