Study on the Effect of Composite Sleeve on Rotor Loss of High-Speed PM BLDC

High-speed permanent magnet brushless dc (PM BLDC) motors rotor is typically protected with a nonmagnetic retaining sleeve. In this paper, a composite sleeve structure with an inner layer of titanium alloy and an outer layer of carbon fiber is designed. It is mechanically robust and present low eddy current loss with the new sleeve. In addition, eddy current loss and torque might be significant in the rotor of a PM BLDC motor and are comparatively analyzed by modifying the thickness of both materials of the new sleeve. After that, to address the problem of increased eddy current losses in PM due to the new sleeve, a composite sleeve with copper shielding is investigated. For the composite sleeve with a copper shield, the effects of the copper shield’s positions and thickness on the rotor losses are studied. Finally, the range of preferred composite sleeve structures is summarized.