The optimization of pole arc coefficient to reduce cogging torque in surface-mounted permanent magnet motors

In this paper, the optimization method of improved domain elimination algorithm (DEA), finite-element method (FEM), and analytical method are combined to optimize the pole arc coefficient of a permanent magnet (PM) to minimize the cogging torque of a permanent magnet motor. Since the cogging torque is very sensitive to the changing of the pole arc coefficient of a PM, the changing of the pole arc coefficient should be very small in optimization. The cogging torque corresponding to many relative positions between magnet and armature must be calculated by FEM to find the peak value for every pole arc coefficient, so in order to reduce the computing time, the feasible region of the pole arc coefficient should be set to as small as possible. In this paper, the analytical method is first used to reduce the feasible region of pole arc coefficient in which the cogging torque is small. Then, improved DEA and FEM are used to find the best pole arc coefficient. After optimization, the cogging torque is greatly reduced, and the computing time decreases notably. Index Terms--Finite-element method (FEM), optimization method, permanent magnet (PM) motors.