Reduction of cogging torque of radial flux permanent magnet brushless DC motor by magnet shifting technique

Abstract

Introduction. In spite of many advantages of radial flux permanent magnet brushless DC motors it suffers from the distinct disadvantage of high cogging torque. The designer must emphasize to reduce the cogging torque during the design stage. This paper introduces magnet shifting technique to mitigate cogging torque of surface mounted radial flux brushless DC motor. Methodology. Initially 200 W, 1000 rpm surface mounted radial flux permanent magnet brushless DC motor is designed with symmetrical placement of permanent magnets with respect to each other on rotor core. Cogging torque profile of this initial motor is obtained by performing finite element modelling and analysis. Originality. This design has been improved by shifting the position of permanent magnets with respect to adjacent permanent magnets. The effect of magnet shifting on cogging torque has been analyzed by performing finite element analysis. Results. It has been examined that the peak to peak cogging torque is decreased from 1.1 N×m to 0.6 N×m with shifting of permanent magnets respectively.

Keywords

• cogging torque
• finite element analysis
• magnet shifting
• permanent magnet brushless dc motor