Influence of Stator Asymmetry on Cogging Torque of Permanent Magnet Brushless Machines

The paper investigates the influence of stator asymmetry on the cogging torque of permanent magnet brushless motors. It shows that high localized magnetic saturation due to such asymmetry can significantly increase the magnitude of the cogging torque and introduces cogging components which have an order lower than the least common multiple between the stator slot number and the rotor pole number. The findings are confirmed by both finite element analyses and measurements on an 18-slot, 6-pole prototype motor.