Comparative study of stator-mounted PM machines focusing on thermal performance

Stator-mounted permanent magnet (PM) machine attracts more and more attention for its high-power density, robust structure and easy for cooling. This paper will provide a comparison focusing on thermal aspect amongst three typical stator-mounted permanent magnet machines, i.e., doubly salient PM machine, flux-reversal PM machine and flux-switching PM machine. To be more comprehensive, a surface mounted PM machine has also been used to compare against the stator-mounted PM machines. The investigated machines have been compared at a wide speed range from 400rpm to 3600rpm because the rotation speed has great impact on loss distribution and heat transfer in the airgap. The computational fluid dynamics (CFD) thermal models of these machines have been built using Ansys CFX software to compare their thermal performances. It is found that, compared to other two stator-mounted PM machines, the flux-switching PM machine, with the highest torque but also the highest losses, always has higher temperature rise (highest peak temperature). Meanwhile, since the windings and magnets are both located on the stator, the magnet temperature of stator-mounted PM machine is very close to their winding temperature.