Comprehensive Comparison of Different Rotor Structures of Low-Speed Permanent Magnet Motor

At present, most of the existing research on low-speed permanent magnet motors (LSPMMs) focuses on the surface-mounted type. There are few other rotor structures, and there is no comprehensive comparison of several widely used rotor structures. A comprehensive comparison of three different rotor structures for low-speed mining motors is carried out, including electromagnetic and loss characteristics, permanent magnet consumption, temperature distribution, etc. Firstly, three rotor structures of a 500 kW, 60 rpm low-speed motor are introduced, and the initial design parameters are determined. Secondly, the influence of each rotor design parameter on the electromagnetic characteristics is analyzed. Next, the electromagnetic optimization of the three rotor structures is carried out, and the motor performance of the three rotor structure optimization schemes is compared, including electromagnetic performance, permanent magnet consumption, motor temperature distribution, etc. Finally, in order to verify the correctness of the theoretical analysis, a prototype is made and tested based on the above analysis. The results show that for the electromagnetic characteristics, when the motors with three different rotor structures meet the performance requirements, the no-load line back-EMF of the inset surface-mounted motor is the lowest, but the back-EMF harmonic content of the inset surface-mounted motor is the highest. The copper loss of the spoke-type motor is the smallest, the efficiency is the highest, and the power factor is the lowest. In addition, the surface-mounted motor has the least consumption of permanent magnets and is more economical. Regarding the temperature distribution, when the same heat dissipation system is used, the temperature of the spoke-type motor with minimum copper loss is the lowest.