Study of Retaining Sleeve and Conductive Shield and Their Influence on Rotor Loss in High-Speed PM BLDC Motors

In the paper, a 2-pole 3-phase high-speed PM BLDC motor with ratings of 3kW @ 150,000rpm is considered, the magnets being SmCo. In order to improve the mechanical strength, the rotor is usually protected with a non-magnetic sleeve, such as a carbon fiber sleeve which has very low electrical conductivity but poor thermal conductivity, or titanium alloy / stainless steel sleeve which has high electrical and thermal conductivity. The influence of different retaining sleeves on the rotor loss is analyzed with FEM.