New technique for reducing cogging torque in a class of brushless DC motors

It is shown that the cogging torque in permanent magnet and brushless DC motors, where the number of magnet poles is close to the number of armature slots, can be reduced considerably by adjusting the width of the poles or the width of the slots. A design method to achieve this goal is presented. The influence of the slot opening on the cogging torque is thoroughly investigated theoretically and experimentally for a prototype.