Mechanical design method for a high-speed surface permanent magnet rotor

Mechanical design of the rotor is an important part of the design process for high-speed electric machines. This paper proposes an analytical method for finding an approximate rotor length and diameter for a surface permanent magnet machine rotor early in the design process. Specifically, the method can be used to find approximate rotor length and diameter dimensions that will balance the need for acceptable factor of safety for rotor sleeve stress and the need for an acceptable separation margin between the operating and critical speeds. Analytical design results are compared to finite element analysis for both the mechanical stress and the natural frequency of the rotor.