Hybrid Cooling Method of Axial-Flux Permanent-Magnet Machines for Vehicle Applications

Thermal properties are a key issue in many applications associated with electrical machines. Because of its special configuration, an axial-flux electrical machine usually uses self-ventilation. However, this cooling method has a significant impact degrading the machine operating characteristics, and thus, an independent cooling system is desirable. The focus of this paper is on the steady-state thermal modeling and laboratory testing of an axial-flux permanent-magnet (AFPM) electrical machine intended for a traction application. The proposed hybrid cooling arrangement consists of a frame cooling circuit with a water flow inside, a set of copper bars inserted in the teeth, and a segment of potting material around the end windings. Computational fluid dynamics and finite-element analysis are applied for the preliminary design. This paper provides experimental verification of the simulation results on a 100-kW AFPM electrical machine.