Analysis and restrain strategy of cogging torque in double-stator permanent magnet brushless motor

As the double-stator motor has two stators, if no techniques are adopted in motor design, the cogging torque of the double-stator motor will increase one time compared to conventional motors, which will decrease the performances of the whole motor system. For the existence of two stators, if the method of the skewing of the stator slots or alternatively of the PMs is adopted to reduce the cogging torque, the motor structure will be more complex. The paper aims at the structure features of this motor, a two dimensional finite element analysis method is used to analyze the main element to influence the cogging torque. The influences of relative position angle of the two stators, the magnet arc length, the inner and outer airgap length, and the combination of different teeth and slots are discussed to restrain the cogging torque. The scheme of staggering two stators to half cycle of cogging torque is provided, and the tests of the prototypes are made to support it.