Multi-Physics Comparison of Surface-Mounted and Interior Permanent Magnet Synchronous Motor for High-Speed Applications

For high-speed permanent magnet machines (HSPMMs), two different rotor structures are widely used: surface-mounted permanent magnet (SPM) and interior permanent magnet (IPM). The two different rotor structures have a large impact on the comprehensive performance in multiple physical fields of HSPMMs, including mechanical stress, electromagnetic characteristics, and temperature distribution. However, the multi-physics comparison of two different rotor structures is rare in the existing literature, which makes it difficult for designers to choose a suitable rotor structure. Therefore, in this paper, the comprehensive performance of multi-physics for SPM and IPM is comprehensively compared and analyzed. Firstly, the SPM and IPM were designed under 60 kW and 30,000 rpm with the condition of the same stator structure, winding type and volume. Secondly, to ensure that the two rotor structures meet the stress-field constraints, a finite element model (FEM) was built in Ansys Workbench. The influence of different parameters on the rotor stress was analyzed. Following this, the electromagnetic characteristics and temperature distributions of the two motors were compared and analyzed comprehensively through the FEM. Finally, a prototype of an SPM rotor structure is selected and manufactured. The validity of the multi-physics analysis and design was verified through experimental measurements. The above analysis will provide a reference when a designer chooses a rotor structure for an HSPMM.