Design issues of high-speed permanent magnet machines for high-temperature applications

This paper deals with the issues associated with the design of high-speed, high torque-density permanent magnet machines which operate in elevated temperature environments. The considerations discussed are described by the design cycle iterations of a 23 kW machine, which runs at a speed of 84 krpm, with a rated rotor torque density of 50 kNm/m³. Particular emphasis is made on the interaction (and conflict) of electromagnetic fields, thermal fields and mechanical constraints in finding an optimum air-gap length for minimum magnet temperature and best overall efficiency.