Characterization of a Nonlinear Resistive Polymer-Nanoparticle Composite Coating for Electric Field Reduction in a Medium-Voltage Power Module

Medium-voltage (MV) silicon carbide power devices are emerging and have the potential to serve in various power grid applications. However, the high blocking voltage and reduced size of the power modules require innovative insulation solutions. In this letter, a nonlinear resistive polymer-nanoparticle composite coating was characterized and, for the first time, demonstrated for reducing the high electric field at the triple point on a patterned substrate of a typical MV power module. The electrical properties of the coating were measured. Its conductivity showed nonlinear dependency on the applied electric field. The coating, which is about 20 
μ
m thick, was applied along the triple-point edges on a patterned direct-bonded copper substrate. The partial discharge inception voltages of the coated substrates were measured in a transformer oil or in a silicone gel. The average increases in the inception voltage compared to the substrates without the coating were over 85% in the silicone gel. The increase agreed with the results of field simulations, which showed a 53% reduction of the maximum field in the silicone gel for a coated substrate. The processing simplicity and effectiveness of the coating present a cost-effective solution for insulating high-power-density, MV power modules.