Design Method of an Ultrahigh Speed PM Motor/Generator for Electric-Turbo Compounding System

This paper presents the design of an ultrahigh speed permanent magnet (PM) motor/generator driven at a rated output and speed of 10 kW and 70 000 r/min, respectively, for use in an electric-turbo compounding system. When designing the very-high speed motor/generator, the mechanical and structural safety of the rotor and losses that occur when the motor operates at high speed should be considered for safe operation. In this paper, the optimal design of the ultrahigh speed PM motor is performed with finite element analysis and structural analysis. Especially, the electromagnetic and structural characteristics based on the sleeve material are analyzed. The optimal design for PM motor, using carbon fiber is proposed not only to reduce the eddy-current loss, which prominently occurs at very-high speed, but also to ensure its structural safety. Finally, the validity of the design method and the effectiveness of the fabricated prototype of PM motor is verified through experimental tests.