Loss Calculation and Thermal Analysis of Rotors Supported by Active Magnetic Bearings for High-Speed Permanent-Magnet Electrical Machines

The rotor overtemperature caused by losses is one of the important issues for the high-speed electric machine. This paper focuses on the loss analysis and thermal performance evaluation for a rotor of 100 kW, 32 km/min high-speed permanent-magnet motor. The rotor temperature distribution based on the finite element method is obtained by accounting for various losses, including air-friction loss of the rotor, iron loss of the active magnetic bearing, and eddy-current loss of the motor. The influence of the stator core temperature on rotor thermal performance is analyzed by using a coupling simulation of fluid-temperature field. The temperature rise measurement of rotor is employed to study the impact of different cooling way on rotor thermal performance and to verify the computational accuracy of losses and temperature distribution. The analysis result of air-friction loss is compared with the measurement, which is obtained from the total losses by using the method of loss separation. It has great significance for the cooling structure design and the efficiency enhancement of electrical machine.