Development of Polymer-Ceramic Composite Materials for the Winding Insulation of Highly Utilized and Energy-Efficient Electrical Machines

The electromagnetic utilization of an electrical machine can be increased by raising the current density, with a limitation resulting from the maximum permissible temperature of the winding insulation. Conventional insulating materials only have a low specific thermal conductivity, which results in large temperature gradients in the winding cross-section and consequently hotspots. The article presents the development and characterization of ceramic-like composite materials based on filled polysiloxanes for the dip coating of lamination stacks and the impregnation of the winding of electrical machines. The specific equivalent thermal conductivity is determined on composite winding samples, the thermal cycle stability is examined and the microstructure is analyzed with the scanning electron microscope. The manufacturability and the partial discharge behavior are examined based on test samples. The results of tests on an electric traction machine are used to show the potential for increasing the power density.