Experimental Sensitivity Analysis of Oil Jet Parameters Impact on Electrical Machines' Thermal Performance

High-performance electrical machines play an important role in achieving the zero-carbon target by 2050 in the transportation electrification sector, with thermal management being a key aspect in electrical machine power density improvement. Oil jet or spray cooling techniques are receiving increasing attention due to their effective cooling capabilities, in particular for hairpin windings in the stator. However, the design of such systems remains challenging due to the complexity of the oil distribution in the end-winding region and airgap. This paper presents an approach to identify the most sensitive parameters affecting the machine cooling performances of such cooling applications prior to full-scale testing. Firstly, a cooling technique is proposed to cool both the stator and rotor for a case study machine. Key variables, including nozzle and machine parameters, are then identified, and screen tests are designed for sensitivity analysis. Results show that the bespoke cooling techniques for the machine result in substantial mechanical losses due to high rotor speed, which cannot be ignored. The impact of other parameters on the machine's cooling performance is also discussed.