Assessment of Experimental Approaches for the Evaluation of Material Compatibility of E-fluids With the Insulation System of Low Voltage Rotating Electrical Machines

With the development of modern electric drive train systems, an effective cooling strategy is becoming a critical issue. Among various cooling methods, direct oil cooling is becoming more popular since it enables it to remove the heat directly from the heat source and subsequently improves the cooling performance. Aside from the cooling performance with direct cooling, the material compatibility of the coolant with machine components, particularly the electrical insulation system, is currently getting more attention. However, practical work regarding this issue is rare. Importantly, there still need to be widely recognised standards or instructions for compatibility evaluation. In the present work, the feasibility of conventional diagnostic approaches of insulation systems for compatibility evaluation is discussed. Particularly, a method to estimate the lifetime of the insulation system considering the compatibility issue is provided, and the role of mechanical stress during the compatibility study is analysed.