Optimization of Cogging Torque in Surface Mounted PM Machines using PM Segmetation

In this paper, the segmentation method is used to reduce cogging torque in the surface-mounted permanent magnet machines. In this method the magnet pole is divided into several magnet blocks. The permanent magnet is segmented in two ways, equal- and unequal- size permanent magnet blocks. In the both methods the half-wave symmetry of the magnetic poles is applied. The dimension of the permanent magnet s is optimized to reduce the machine cogging torque using an analytical model combined with the genetic algorithm. The effect of the slotted armature is taken into account in the analytical model. The cogging torque is obtained from the air gap magnetic flux components and the Maxwell’s stress tensor. The model is obtained by solving the Poisson’s equation. This model is used as a fast tool to compute the objective function in the genetic algorithm. In addition, the validity of the proposed model is verified with finite element analysis.