Investigation of Cogging Torque Comprehensive Reduction Method in High Precision Servo Permanent Magnet Motor

In servo applications with high positioning accuracy, cogging torque has become the key problem to limit the improvement of motor positioning performance. Sometimes a single cogging torque reduction method can't meet the needs of special applications. In this paper, a method of cogging torque comprehensive reduction from the perspective of harmonics was proposed for high precision servo permanent magnet motor. Firstly, the working principle of different cogging torque reduction methods are given. Then, the pole slot fit was designed to increase the number of cogging torque cycles, and three-multiple harmonics of cogging torque becomes the main component after rotor magnet three-step skewing. Finally, magnet arc and slot opening optimization were employed to reduce the three-multiple harmonics of cogging torque, at the meanwhile, the other harmonics of cogging torque was further reduced. The optimal design motor cogging torque was reduced to 0.62% of the initial design, when the rated torque increased 3.5%.