Optimization on the tooth top shape of a high speed permanent magnetic generator

Abstract

Currently, there is significant attention being paid to the development of high-speed machines including motors and generators. In particular, permanent magnet machines are gaining more traction due to their outstanding efficiency, high power density, small size, low weight, simple mechanical construction, easy maintenance and good reliability. The higher the motor speed, the smaller the electric machine volume for the same power output. However, the heat or loss density of the machine is proportional to its power density, and the structure design aiming to better the loss distributing becomes a practical challenge for high speed machines. To ensure that the magnets or rotor bars can be retained safely, often a metal is designed on rotor outer surface, and large eddy loss would be generated while machine operating with a very high frequency electromagnetic field. In this case, scholars make efforts to minimize eddy current losses whilst providing mechanical integrity, which may benefit both the machine efficiency and thermal management. In this paper, a 3kW, 80k rpm high speed permanent magnetic generator is investigated, and its stator tooth top shape is optimized to reduce eddy losses in the rotor sleeve. During the process some other output performance parameters are considered by the proposed optimization mathematical model.