Zeroization of Cogging Torque of Permanent Magnet Machines by Optimizing Rotor Surface Shape: Comparison between Surface and Interior Types

In this paper, we investigate the mechanism of cogging torque reduction by optimizing the rotor surface of permanent magnet synchronous machines. The optimizations of both the surface and interior permanent magnet machines are carried out. It is clarified that the cogging torques of both the machines can be reduced to be nearly zero by optimizing the rotor surfaces, whereas the mechanisms of cogging torque reduction of these machines are completely different from each other.