Study of Rotor Slotting on Cogging Torque of Spoke-Type Permanent Magnet Machine

Compared with the traditional interior permanent magnet (PM) machine, the spoke-type permanent magnet (STPM) machines have higher cogging torque due to high air-gap flux density and double slotting. This paper investigates the influence of rotor slotting on cogging torque for STPM machine. Firstly, the cogging torque generating mechanism of STPM machines is revealed based on the magnetomotive force model, and the expressions of the cogging torque is obtained. Then, the variation rules of cogging torque versus STPM machine parameters are researched and analyzed based on finite element method (FEM), including stator slot width, rotor slot width, and so on. In addition, the optimal machine is obtained to minimum cogging torque, and the electromagnetic performance between the initial and optimal machines is compared. Finally, a 16 kW STPM machine prototype is manufactured for experimental testing, and verify the accuracy of FE results.