Thermally conductive polymer composites for thermal management of electric machines: A modeling and experimental study

Abstract

With ever-increasing drive to improve the power output of electric machines and reduce heat accumulation based insulation failure, efficient thermal management is highly desirable. Increasing thermal conductivity of impregnation resin is critically important for thermal dissipation in electric machines. In this work, we investigated how the improvement in thermal conductivity of impregnation resins could benefit the heat dissipation of electric machines. To this end, a two-dimensional (2D) finite element analysis (FEA) was conducted, which revealed that increasing the thermal conductivity of impregnation resins to 0.6–0.8 W·m−1·K−1 could significantly decrease the winding temperature. Meanwhile, epoxy-based composites with different thermally conductive fillers were synthesized. The effect of filler type/loading on thermal conductivity and viscosity were investigated. After systematically measuring the thermal conductivity and viscoelastic properties of these composites, a “viscosity-thermal conductivity” correlation was plotted to sort out candidate resin for impregnation trials. In addition, impregnated prototypes comprising enamel wires and both neat epoxy resin and thermally conductive composite impregnation resins were fabricated. Under both natural and forced convection, the epoxy/BN composite resin was shown to be effective in reducing the core temperature of prototype by 9.1–18.6 °C compared with neat epoxy-impregnated prototype. The results indicated that thermally conductive polymer composites had the potential to greatly improve thermal management of electric machines. The findings in this work provide insights and guidelines for future development of thermally conductive impregnation resins.