Effectiveness of thermal interface materials on electrical machines thermal performance with heat pipes

Thermal issue has always been a major concern in motor design. Heat pipes (HPs) have been applied in electrical machines with remarkable cooling effects reported. However, critical factors that affect HP thermal benefits have rarely been studied, such as limited contact area between HPs and heat sources, which may lead to high thermal resistance and degrade motor thermal performance. Due to limited thermal conductivities, conventional motor thermal interface materials (TIMs), such as epoxy resin, fail to maximize HP thermal benefits and minimize motor temperature rise. In this case, new TIMs with outstanding thermal properties that have not been used in electrical machines, such as thermal grease and adhesive, are potential candidates to address this issue, while their thermal impact is still unclear. This article conducts both experiments and thermal analyses to quantify the effects of TIM on motor cooling performance. Firstly, the thermal properties of ten typical TIMs in four categories are experimentally characterized. Then, the selected TIMs are applied to a stator-winding assembly with HP to evaluate their thermal impact on motor cooling performance under different cooling conditions. Finally, practical guidelines are given for TIM selection in electrical machines with HPs or other cooling media.