Cogging torque analysis and minimization of axial flux PM machines

This paper defines three indexes for the cogging torque waveform and analyzes the effect of slot opening ratio and pole-arc ratio on the three indexes of cogging torque waveform in theory. Two measures to reduce cogging torque of the axial flux PM machines are discussed and analyzed. Using the quasi-3D analysis method, the mechanism of cogging torque minimization for axial flux PM machines equipped with several special magnet shapes is explained by detailed sector results. Finally, a novel method based on magnet shape prediction is proposed for cogging torque minimization.