Interaction Effects of PM Tolerances and Rotor Eccentricities on Cogging Torque of 12-slot/10-pole PM Machines

This paper investigates the interaction effects of permanent magnet (PM) tolerances and rotor eccentricities of 12-slot/10-pole PM machines by finite element method (FEM) and phasor analysis. It is found that the relative location between diversified PMs and eccentric rotor have a significant effect on cogging torque. (a) When a weak (e.g., thin thickness) PM is close to the minimum airgap, rotor static eccentricity and PM tolerances have a strengthening effect to deteriorate cogging torque, but rotor dynamic eccentricity and PM tolerances have a weakening effect to reduce cogging torque. (b) When a strong (e.g., thick thickness) PM is close to the minimum airgap, rotor static/dynamic eccentricity and PM tolerances always have a strengthening effect to deteriorate cogging torque. The experiments verify the FEM-predicted cogging torques and the interaction effects between PM tolerances and rotor eccentricities on cogging torque in the 12-slot/10-pole PM machine.