Analysis of Exciting Forces in Brushless DC Motors With Segmented Poles

摘要

This paper investigates effects of segmented poles on motor performances such as coggnign torque, BEMF, phase currnet, torque ripple and local forces. The analysis is based on a permanent magnet brushless DC motor usign FEM analysis. Effective dead zones at pole separations result in wider than the physical dead zones due to leakage field durign magnetization. Segmented poles inevitably cause uneven magnetic field distribution at pole separations which introduces additional harmonics of exciting forces which are detrimenteal to structural resonances. They also decreases motor efficinecy by reducing effectiven phase BEMF.