Cogging torque reduction techniques for axial-flux surface-mounted permanent-magnet segmented-armature-torus machines

Cogging torque is a parasitic element that causes mechanical vibration, noise and undesirable starting effects in permanent magnet (PM) machines. Significant design efforts, therefore, are made to minimize cogging torque in high performance PM machines. In this paper, several cost effective displacement techniques are proposed for the design of axial-flux surface-mounted permanent-magnet (AFSMPM) segmented-armature-torus (SAT) machines. Quasi-Three-dimensional (quasi-3-D) analytical and three-dimensional finite-element (3-D FE) methods are employed in order to study the effects of the techniques on the reduction of cogging torque in two 5-kW AFSMPM SAT machines. The validity of the proposed quasi-3D analytical model, and the effectiveness of cogging reduction techniques, are demonstrated by comprehensive FE-simulation results.