Abstract: High power density is critical to high-performance electrical machines in aviation, and the rotor structures of the machines play an essential role. This paper focuses on the permanent magnet (PM)-shifting rotor to enhance the power density and PM utilization ratio of the PM synchronous machines. Aimed at the rated operation point with the power of 150 kW and the speed of 12000 r/min, the global optimizations based on Non-dominated Sorting Genetic Algorithm-II (NSGA-II) optimization algorithm are applied to the surface-mounted, surface-inserted, and surface-inserted-shifted PM machines individually, and then the three optimal machines are comprehensively evaluated and compared. Furthermore, the comparative investigations on the surface-inserted-shifted PM machines with different structures and different PM shifting angles, are carried out. It is revealed that the surface-inserted-shifted PM machines can exhibit 2.1% higher power density, 17.6% lower PM usage, and 11.6% lower torque ripple than the conventional surface-mounted PM machines, indicating good potential for aircraft applications.

Key words: high power density machine, permanent magnet synchronous machine, permanent magnet-shifting, NSGA-II optimization algorithm