Design features of high speed PM machines

The high-speed permanent magnet (PM) machine has been widely investigated since it has small size, high efficiency and power density. However, due to the high rotor speed and high frequency of the stator flux variation, the design of a high-speed machine is quite different from designing a conventional machine with low speed and low frequency. As a example, the design features of a high-speed PM generator driven by micro turbines are introduced in this paper. The choice of rotor structure, the design of stator core and winding, the bearing structure and the control system are discussed in some details.