Cogging torque minimization in flux-switching permanent magnet machines by tooth chamfering

Due to the nature of doubly salient structure and high air-gap flux density, flux-switching permanent magnet (FSPM) machines typically suffer from large cogging torque, causing undesired acoustic noise and vibration, especially at low speeds. In this paper, various tooth chamfering methods for a 12/10 FSPM machine are proposed to reduce cogging torque. The influences of both circular bead and right angle as well as their possible combinations on cogging torque are investigated by 2D finite element analysis (FEA), and it turns out that employing right angles in both stator and rotor teeth is the most effective solution. Further, in order to explain this phenomena, the air-gap flux density is analyzed. Besides, the impacts on phase back electro-motive-force and electromagnetic torque are also evaluated. The predicted results indicate that the proposed technique can significantly reduce the peak value of cogging torque from 2.6Nm to 0.4Nm, while the reduction of average torque is only about 1.6%, which turns out to be an improvement when compared with the approach employed in previous literatures.