Rotor Design and Optimization of High-Speed Surface-Mounted Permanent Magnet Motor Based on the Multi-Physical Field Coupling Method

A novel scheme based on the multi-physical field coupling method was proposed for rotor design of the high-speed surface-mounted permanent magnet motors. Based on the analysis of rotor material and strength theory, the strength checking criteria for different types of rotor materials were summarized. The technical parameters of a high-speed permanent magnet motor were preliminarily designed, and the electromagnetic field simulation was adopted to verify the rationality of the designed scheme. Then, the minimum rotor sheath thickness was taken as the objective function to carry out a multi-field coupling simulation. On the premise that the motor can operate safely at high speed, the minimum sheath thickness is 1.15mm, and the interference fit size between the permanent magnet and the sheath is 0.098mm. On this basis, the calibration criteria of rotor sheath strength, permanent magnet strength and interference fit contacting pressure was put forward. When the optimized sheath was adopted, the total loss of the motor is reduced by 4.03W and the average output torque is increased by 6.37mN
$\cdot \text{m}$
. Then an accurate lumped parameter thermal network model was constructed to solve the temperature field parameters of the motor. Two high-speed permanent magnet motor s were developed to verify the accuracy of the theoretical study. The experimental data illustrate that the maximum error between the temperature obtained from the lumped parameter thermal network model and the actual temperature is less than 4.30%, and the steady-state temperature of each position of the optimized high-speed permanent magnet motor decreases. The research methods and conclusions of this paper can be extended to the rotor sheath design and optimization of other high-speed permanent magnet motors.