Designing a Coreless High-Speed Axial-Flux PM Generator for Microturbines

Compactness and lightness make high-speed axial-flux machines eligible for distributed generation application with microturbine. In a high-speed generator driven by micro-turbines, the rotor speed is normally above 30,000 rpm and may even exceed 100,000 rpm. The frequency for flux variation is more than 1 kHz. Therefore, designing such a high-speed generator is quite different, in mechanical and electromagnetic respects, from designing conventional generators with low speed and low frequency. Important considerations in designing high-speed axial-flux generators (HSAFG) for microturbine are discussed in this paper. Results of the efficiency sensitivity versus air gap of the machine are also presented.