A new approach to analysis and mitigation of PM motor cogging torque

Torque pulsation reduction of permanent magnet synchronous motor (PMSM) is an important design issue. One component of this pulsation is cogging torque, which depends on magnetic configuration of stator and rotor (e.g., magnets and slots shape and dimensions). This paper presents a new physical and mathematical analysis of cogging torque for surface mount PM (SFPM) motor. Based on the analysis, a mathematical formula is derived for the cogging torque and verified by FEM simulation. Based on the presented analysis, a new method of air-bridge shaping to reduce cogging torque is presented for an interior PM motor (IPM). The FEM result shows significant reduction of the cogging torque, due to new air bridge design.