Effect of Eccentric Tooth Tip Arc on Cogging Torque of PM Machines

This paper proposes an eccentric tooth tip arc on a stator for a reduction in the cogging torque of permanent magnet synchronous machines (PMSM). The proposed technique is applicable for both inner rotor and outer rotor PM machines. The variation in the stator tooth geometry and a corresponding change in the tooth tip arc of the eccentric tooth is derived mathematically. Two different PM synchronous motors, i.e. 12-slot/10-pole inner rotor and 12-slot/14-pole outer rotor PMSM are taken for this study to analyze the effect of the proposed method. A detailed finite element analysis (FEA) is performed on both the machines, and their cogging torque is analyzed. It is found that the cogging torque reduces with an increase in the eccentricity of the stator tooth tip arc.