Simultaneous improvement of cogging torque and torque density in axial flux-switching permanent magnet motor

Abstract

Axial Flux-Switching Permanent Magnet motors are broadly used in various industrial applications due to their high torque density and low rotor inertia. However, one major drawback of these motors is their cogging torque, which results in torque ripple and vibration. Existing methods for reducing cogging torque have often led to a decrease in useful electromagnetic torque, thereby compromising motor efficiency. To address this issue, a novel hybrid structure for the simultaneous improvement of cogging torque and electromagnetic torque in Axial Flux-Switching Permanent Magnet motors is presented. The proposed structure combines the optimal arc coefficient of the rotor pole technique with the notching rotor technique, resulting in a new motor configuration that exhibits both reduced cogging torque and increased torque density. Analytical equations for calculating cogging torque are derived, and 3D finite element analysis is conducted to evaluate the effectiveness of the proposed structure design. Furthermore, the optimal values of the arc coefficient and forming angle of the rotor pole are determined using the Taguchi analysis. Comparing the results of the optimal motor structure with the previous design shows that the new structure can improve the cogging torque, average electromagnetic torque, torque ripple, torque density, and peak torque output of the motor, which confirms the effectiveness of the proposed structure.