LAUSR

A rotor retaining sleeve is mechanically necessary in the structure of high-speed SPM machines to prevent structural failure. However, the significant eddy current loss within metal sleeves leads to a reduction in electromagnetic efficiency and serious thermal and mechanical issues. Therefore, several techniques and methods have been proposed and developed to reduce such losses. In this paper, a helical retaining sleeve is proposed to reduce losses by cutting the flow path of the eddy currents. Using FEA, a comparison is made of the electromagnetic and mechanical performance of the proposed sleeve against a conventional sleeve having the same material and dimensions. It is concluded that the eddy current loss reduces significantly when the helical sleeve is used, whereas the mechanical stress is broadly unchanged in the central region of the rotor with only a small increase around the ends when compared with the conventional sleeve.