Optimum design of ultra high speed hybrid rotor of PM machines

For the ultra high speed PM rotor, a metallic sleeve is usually interference fitted onto a cylinder or ring shaped PM to against the huge centrifugal force. The initial interference hinges not only on the loose of the rotor, but also strongly on the strength of the PM and the sleeve. In order to determinate the initial interference, this paper proposes an analytical model of stress/displacement field of the rotor which is verified by the Finite Element (FE) Method. Then, the initial interference which facilitates the optimal design of this type of rotor is deduced.