Analysis of Nonlinear Conductivity Coating used to Improve Electric Field Distribution in Medium Voltage Power Module

By establishing a finite element simulation model in COMSOL, the electric field distribution of a 15kV power module is analyzed, and the local maximum electric field is reduced by using nonlinear conductivity materials. The characteristics and coating length L of nonlinear conductivity materials are analyzed in detail. The simulation results show that with the increase of the L , the electric field decreases, and the leakage current increases. When the trench is completely coated, the peak electric field can be decreased by 84% and the leakage current will be increased by 20%. Considering the difficulty in controlling the length of coating in practice, coating the entire trench is suggested. It is identified that the efficient peak electric field mitigation of the non-linear conductivity coating requires engineering the coating parameters to both geometry and operating conditions. In the configuration studied in this paper, optimum nonlinear coating parameters are identified to be a switching field of 7.5kV/mm and a low-field conductivity of 10 −11 S/m to achieve low electric field, low leakage current, and simple operation.