Select Variables Affecting Thermal System Design of a Liquid-Cooled Stator

NASA Glenn Researchers have endeavored to create a high-power-density, efficient electric motor called the High Efficiency Megawatt Motor (HEMM) with a goal of exceeding 98% efficiency and 1.46 MW of power. These aggressive goals were set because increasing the power density and efficiency of electric machines (motors and generators) is integral to bringing electrified aircraft (EA) to commercial realization. Resistive losses in the stator windings are by far the largest (34%) contributor to this design’s total energy losses. Previous testing of a HEMM-like stator test article (statorette) showed good agreement between measured performance and model predictions. Therefore, a foundation was provided to test other engineering parameters that are encountered when designing an electric machine. Of particular interest are the effects of changes to the thickness of the epoxy from the potting process, changes in the fluid volume/flow path around the end windings, and changes in the viscosity of the cooling fluid on the overall thermal performance of the unit. The impact of those parameters as revealed through a third-generation build, test, and finite element model analysis of a statorette test section is the focus of this paper.