Modeling and Fast Evaluation of Cogging Torque in Halbach Array Surface-Mounted Permanent Magnet Motors Considering Manufacturing Tolerances

Manufacturing tolerances usually result in additional cogging torque harmonics in surface-mounted permanent magnet synchronous motors (SPMSMs), which may lead to an increase in cogging torque. This paper establishes an analytical model for the cogging torque of SPMSMs using the complex permeance function and the energy method. With the aid of the analytical model, the origin of cogging torque harmonics under the influence of different types of tolerances is elucidated. Then, a field reconstruction method (FRM) is proposed to rapidly predict magnetic field variations in Halbach array SPMSMs due to magnet manufacturing tolerances. Based on FRM, a semi-analytical method is proposed for the fast evaluation of cogging torque considering manufacturing tolerances. The correctness of the analysis and the effectiveness of the semi-analytical method are verified through finite element analysis on a 6-slot/4-pole Halbach array SPMSM. Finally, the computational cost and application scenarios of the proposed method are discussed using two examples. The analysis is validated through testing on a prototype.