Sensitivity Analysis on Electrical Machines Mechanical Losses with Oil Jet Cooling

Thermal aspect is a key enabler for highperformance electrical machines in the transportation sector to accelerate the path to net zero carbon by 2050. Oil jet/spray cooling is proposed as an effective cooling technique in electrical machines to remove losses in the armature coil, where most existing literature focuses on the thermal performance only. The associated mechanical losses due to oil impingement into the end region of the machine are, however, rarely reported. This paper proposes an oil jet/spray technique to cool both rotor and stator end windings. Various oil jet-related parameters are investigated experimentally to understand the oil particle distribution in the machine end region, as well as the correlations between the machine losses and jet key parameters. The cooling concept will be first introduced with a test plan in this paper, as well as an analytical analysis to understand the impact of key parameters on the mechanical losses. The sensitivity analysis of key parameters on the oil-related mechanical losses will then be presented. This provides quantified guidelines to improve the cooling performances of jet/spray cooling without significantly increasing mechanical losses.