Compatibility Study of Water-Based Lubricants and Insulation Systems in Low-Voltage Electrical Machines for Automotive Applications

Direct oil cooling is widely employed in electric drive systems to enhance power density. However, conventional oils’ thermal limitations restrict their cooling efficiency. To overcome this challenge, TotalEnergies has developed a water-based lubricant (WBL) as an alternative direct cooling medium. This study investigates the compatibility and electrical behavior of insulation components in electrical machines exposed to WBL, focusing on enameled wires and insulation paper at temperatures up to 100°C. Two WBL formulations with different additive compositions are tested to assess their impact on insulation compatibility. The results indicate that WBLs demonstrate compatibility with insulation components at 70°C. Furthermore, compared to the first kind of WBL, the second WBL shows better compatibility than the first WBL in various indexes. It clarifies that the additives in the WBL can be optimized to enhance its compatibility with insulation systems at higher temperatures, offering a promising avenue for improving the cooling performance of electric drive systems.