Minimization of Cogging Torque in Fractional-Slot Axial Flux Permanent Magnet Synchronous Machine with Conventional Structure

This paper studies minimization of cogging torque in fractional-slot winding axial flux PM machines without skewing rotor magnets or displacing stator slots. Fractional winding has small cogging torque which is highlight for applications such as wind turbines. Cogging torque is caused by interaction between rotor magnets and stator core. The axial flux PM machine has an unique structure that the slot dimensions is usually constant and by varying slot opening and pole arc ratio, cogging torque could be minimized. In this paper, cogging torque of fractional-slot concentrated winding was further reduced by proposed method.