Effects of segmented poles on motor performances

This paper investigates effects of segmented poles on motor performances such as cogging torque, back electromotive force (BEMF), phase current, torque ripple and local forces. The analysis is based on a permanent magnet brushless DC motor using FEM analysis. Effective dead zones at pole separations result in wider than the physical dead zones due to leakage field during magnetization. Segmented poles inevitably cause uneven magnetic field distribution at pole separations which introduces additional harmonics of exciting forces which are detrimental to structural resonances. They also decrease motor efficiency by reducing effective phase BEMF