This paper presents a comprehensive overview of the latest studies and analyses of the cooling technologies and computation methods for the automotive traction motors. Various cooling methods, including the natural, forced air, forced liquid and phase change types, are discussed with the pros and cons of each method being compared. The key factors for optimizing the heat transfer efficiency of each cooling system are highlighted here. Furthermore, the real life examples of these methods, applied in the latest automotive traction motor prototypes and products, have been set out and evaluated. Finally, the analytical and numerical techniques describing the nature and performance of different cooling schemes have been explained and addressed. This paper provides guidelines for selecting the appropriate cooling methods and estimating the performance of them in the early stages of their design. Index Terms-Automotive applications, cooling, traction motors, thermal analysis, numerical analysis. NOMENCLATURECross section area of heat path (m 2 ). , Linear current density (kA/m). , Inlet and outlet cross section areas (m 2 ). Specific heat capacity (J/kg). Diameter (m). , Friction loss factor (dimensionless). Gravitational attraction force (m/s 2 ). Grashof number (dimensionless). Fin extension (m). ℎHeat transfer coefficient (W/m 2 K). ℎLatent heat (kJ/kg). Loss coefficient (dimensionless).

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This paper presents various solutions for the power traction motors of electrical vehicles. Equivalent designs to those commercially available on the roads are investigated. Potential simple modifications of the winding configurations and cooling system are studied: (a) flat wire (hairpin) winding vs stranded round wire in induction, synchronous permanent magnet and wound field machine topologies, (b) winding material grades effect-copper vs aluminum, (c) cooling systems-water jacket vs spray, fluid properties and flow rate.

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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.