Method to reduce the cogging torque of spindle motors

The cogging torque of a spindle motor can be reduced by arcing the salient poles of the stator or by modifying the magnetization profile of the rotor magnet. By arcing the shape of the salient poles, the cogging torque can be reduced to a specific amount. After the primary (elementary) salient pole shape is determined, rotor magnets magnetized by different magnetization fixture shapes and magnetization current values are investigated with the goal of holding the torque constant of motors as well as reducing the cogging torque. We have demonstrated that the cogging torque can be reduced to 4 g cm without sacrificing the torque constant of the motor by properly reshaping the magnetization fixture as well as reshaping the stator.