Cogging torque is often a principle source of vibration and control difficulty in precision spindle motors, especially at low speed and loads. According to energy method, it can be said as coenergy variation in the motor as the rotor rotates. Coenergy stored in different materials of the motion is calculated to observe coenergy variation as the rotor rotates. It shows that most of the variation occurs at permanent magnets and stator slots when pole transitions pass by stator slots. Notches on the stator teeth can act as additional slots in the stator, thus reducing coenergy variation as the rotor rotates. It shows that proper notches on teeth can effectively eliminate cogging torque in permanent magnet motors.
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