Investigation on the Influence of Eccentricity on the AC Copper Loss of High-Speed Slotless Permanent Magnet Motor

The armature winding of slotless motor is directly exposed to the air-gap magnetic field. During high-speed operation, the effective part of the armature winding cuts the flux lines directly, which would inevitably cause large ac copper loss. Moreover, when the rotor is eccentric, appreciable distortions would be appeared in the air-gap flux density. The additional flux density would aggravate the ac copper loss. In this article, the mechanism of ac copper loss of high-speed slotless motors is explained first. Then, the influence of eccentricity on ac copper loss is evaluated. Finally, the difference in the effect of dynamic and static eccentricity on ac copper loss is compared.