This paper investigates the effect of the inlet configuration on cooling for an air-cooled axial-flux permanent-magnet (AFPM) machine. Temperature rises in the stator were measured and compared with results predicted using computational fluid dynamic (CFD) methods linked to a detailed machine loss characterization. It is found that an improved inlet design can significantly reduce the stator temperature rises. Comparison between the validated CFD model results and the values obtained from heat transfer correlations addresses the suitability of those correlations proposed specifically for AFPM machines.

Air-cored machines offer benefits in terms the elimination of magnetic attraction forces between stator and rotor. With no iron in the stator there is not a good thermal conduction path for heat generated by Joule losses in the stator winding. Results from both models and experimental tests are provided in this paper to investigate different methods of cooling air-cored windings, including natural air-cooling, direct liquid cooling and the use of heat pipes.

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