Pole optimization of brushless DC motor

For the tangentially magnetized brushless DC motor used for air compressor, the pole embrace and eccentricity are optimized with 2D FEM (finite element method) to decrease the torque ripple. For the pole embrace optimization, seven different pole arc angles are compared, and 60 /spl deg/ is considered as the best one. For the pole eccentricity optimization, five schemes are put forward and compared, and the half eccentric pole scheme is recommended as the best eccentric one considering average torque, torque ripple percentage and manufacturability. Two prototype motors were made and torque curves were tested. The tested and calculated results are consistent, which proves the correctness of the magnetic field calculation.