The thermal management of electric motors has received significant attention in the last decade. This can be attributed to the need for higher power density motors used in electric vehicles, the thermal aging of insulation material, the demagnetization of permanent magnets, and the deterioration of electromagnetic performance at elevated temperatures. Additionally, temperatures exceeding the expected values (hotspots) in the motor components can result in significant thermal stresses followed by assembly failure. Owing to this, the scientific community has proposed several thermal management techniques of varying complexity and cost. The current work suggests novel designs based on two different cooling techniques: air and liquid.

Totally Enclosed Fan-Cooled (TEFC) motors primarily dissipate heat through the housing. Thus the thermal performance of this class of motors mainly depends on the efficient design of the housing. Numerous studies in the literature focus on optimizing the housing parameters; however, the shape of finned housing has received limited attention. The current computational study proposes and compares the thermal performance of three alternate housing designs (Designs 2, 3, 4), each composed of the same mass as the conventional housing (Design 1). A simplified three-dimensional model for studying these housings is proposed and validated with reasonable accuracy using empirical correlations. Results illustrate that the highest heat transfer coefficients with improvements in the 5-16.5 W/m2.K range are obtained for Design 2 over Design 1. However, the lowest base temperatures with a reduction in the 18-48oC range are obtained for Design 4. All the proposed designs exhibit better thermo-hydraulic performance than the conventional design, and Design 2 shows a maximum improvement of 16%.

Peripheral liquid jacket cooling is still predominantly employed, despite the advent of innovative solutions for the thermal management of electric motors. Of the three common topologies, namely, spiral, axial, and circumferential, limited studies exist on circumferential jacket cooling. The current study examines the impact of the number of turns and mass flow rate to arrive at a base configuration. Variants of this base configuration with bypasses and spoilers are proposed; the influence of bypass parameters and the number of spoilers on heat transfer and fluid flow characteristics are studied. Results indicate that the best combination of bypass parameters can reduce the pressure drop by 33% with marginal influence on heat transfer. Spoilers lower the maximum temperature by 2oC but also increase the pressure drop by nearly 80%. Depending on the design requirements, these suggested variants offer the designer a choice for a configuration suitable to industrial applications and practical situations.