A method for reduction of cogging torque in brushless DC motor considering the distribution of magnetization by 3DEMCN

A method of reducing cogging torque and improving average torque has been studied by changing the dead zone angle of trapezoidal magnetization distribution of the ring type rotor magnet in a brushless DC motor (BLDCM). Because the BLDCM has a 3-D shape of its overhang, 3-D analysis should be used for exact computation of its magnetic field. A 3-D equivalent magnetic circuit network method (3-D EMCN) which can analyze an accurate 3-D magnetic field has been introduced. The analysis results of cogging torque using this 3-D EMCN are compared with those of the 3-D finite element method (3-D FEM) and experimental data.