Cogging torque reduction of a single-phase brushless DC motor

In this research, the cogging torque of a newly designed single-phase brushless DC motor used in CD-ROM application is investigated. A finite element method is employed to numerically analyze the magnetic field distribution inside the motor, in which a three-dimensional mesh is constructed. The torque due to the magnetic coupling between the rotor and stator is estimated based upon the virtual work concept. It is proposed in this paper that the salient pole be divided into several regions in the azimathal direction. By properly choosing the radii for these regions; the cogging torque can be greatly reduced.