Air friction loss calculation of high speed permanent magnet machines

The air friction loss on the rotor surface for a high speed machine can take a large part of the total losses and it is difficult to be determined theoretically or experimentally. In this paper, a calculation method of air friction loss for high speed machines based on fluid field analysis is introduced. The influences of rotor speed and air gap structure on the air friction loss are discussed. The experimental results of machine losses at different operation speeds for a high speed PM motor are presented. A method to separate the air friction loss from the tested total losses of the high speed machine is introduced.