A Study on Stator Shape to Reduce Cogging Torque and Torque Ripple of Double-Layer Spoke Type PMSM

The spoke type permanent magnet synchronous motor (PMSM), which is a general ferrite magnetic flux concentrated motor, has a low portion of reluctance torque at the total torque magnitude. Therefore, as a way to increase the reluctance torque, there is a double-layer spoke type PMSM that can maximize the difference in inductance between the d-axis and the q-axis. However, in the double-layer spoke type PMSM, cogging torque, torque ripple, and total harmonic distortion (THD) of Load Line EMF increase as reluctance torque is maximized, which is the main cause of vibration and noise. As a representative method, it can be solved by applying skew to the rotor, but the conventional method of applying skew is not a good method in terms of productivity because it is difficult to manufacture because it divides the stages of the permanent magnet. Therefore, in this paper, the skew is not applied to the rotor and the asymmetrical design of the shoe is carried out in the stator. Then, we propose a new stator shape that can apply a Skew-like effect by cross-stacking stators using the asymmetric designed stator. Based on the method, the reduction of cogging torque and THD was verified by Finite Element Analysis (FEA).