Degradation Validation Approach for Robust Oil Jet Motor Cooling Designs in an Automotive Powertrain

The development of the next generation electrical vehicles requires drive-trains to become more compact, high-performant, and robust at the lowest possible cost. These more compact drive-trains operate at the same power ratings as their bigger sized equivalent and do need to dissipate their heat in a smaller volume. Therefore, more advanced liquid cooling methods of the drive-train components are needed to enhance the heat removal and increase the compactness, i.e., power density. Recent studies showed the high potential of direct oil jet cooled motor windings as one of the most promising cooling solution. However, several challenges need to be tackled to make such a jet cooling method robust. Therefore, this paper presents a method on how to achieve a robust oil jet cooled design systematically. From a pre-selection of an oil matching the lubrication & cooling conditions of the powertrain, an expert selection of sub-component materials for the motor design, the best robust motor design have been determined. This has been achieved via a degradation validation guide which includes standard oil-material degradation tests, electrical insulation, DC break down voltage tests, and a final motor testing validation phase.