Performance Analysis of Different Skewed Poles Schemes for a 160W Brushless DC Motor

The cogging torque of brushless DC motors is crucial for reducing torque ripple and improving the control accuracy of speed or position. In the literature on weakening cogging torque through skewed poles, the changes in the torque-speed characteristic brought by skewed poles are usually ignored. In this paper, for a 160W brushless DC motor, three skewed poles schemes are proposed based on upright aligned permanent magnet: offset 1/4 pole, offset 1/2 pole, and continuous skewed pole. Cogging torque and torque-speed characteristics of upright alignment and three skewed poles schemes are compared and analyzed by finite element analysis using MagNet software and prototype experiments. Among three skewed poles schemes, cogging torque of offset 1/4 pole is relatively small, and the change in speed with torque is relatively small.