Abstract: When the ultra-high-speed permanent magnet motor is running, the permanent magnet in the motor will be damaged because of the huge unbearable centrifugal force. In order to solve this problem, based on an ultra-high-speed permanent magnet motor, the mechanical strength of motor rotor was simulated and studied experimentally. Firstly, based on an ultra-high-speed permanent magnet motor, the stress finite element simulation was carried out, and the influence degree and sensitivity of sheath thickness, interference, temperature and rotation speed on rotor stress were analyzed. Then,a high-mechanical strength rotor design scheme of the ultra-high-speed permanent magnet motor was obtained based on the above analysis results,and the rotor stress under different operating conditions was checked. Finally,an ultra-high-speed permanent magnetic motor with a rated power of 7kW and a rated speed of 150000r/min was produced, and mechanical strength experiment and no-load characteristics test were performed to verify the theoretical analysis. The experimental results indicate that the stress of permanent magnet is compressive stress under different operating conditions, its maximum value is 109 MPa, and the safety factor is greater than 6, indicating that the permanent magnet stress still has a large margin. The maximum stress of the sleeve is 967MPa, and the safety factor is greater than 2, indicating that comparing with permanent magnets, the sleeve is easier to reach the ultimate mechanical strength. At the same time, the no-load back electromotive force of the prototype under rated operating is 362V, the consistency with the calculated value is above 98%, and after a few hours of operating, the rotor structure is not damaged. The results indicate that the designed rotor has high reliability and can meet the needs of ultra-high-speed operation.
Key words:  ultra-high-speed permanent magnet motor; rotor mechanical strength; sensitivity; stress analysis; sheath thickness; rotation speed