Electric-Field Reduction at High Temperature of a Bulk Nonlinear Resistive Insulation for Medium-Voltage Power Module Packaging

A field-dependent conductivity (FDC) bulk insulating material, composing of solely submicron-silver fillers and silicone gel matrix, is proposed for the first time to reduce the electric-field (E-field) concentration at triplepoint in a medium-voltage (MV) power module. Over a broad temperature range of 20 200dddddddddddddddC, the direct-bondcopper (DBC) sample with FDC bulk insulation was thoroughly investigated. This included tests of their nonlinear conductivity versus E-field of 1 20 kV/mm, simulations of the E-field grading effects, and verification of increased partial discharge inception voltage (PDIV) values. The nonlinear conductivity increases with E-field and temperature, which is essential for raising PDIV by E-field grading. The mechanisms of nonlinear conductivity were explained by the Schottky effect, Poole-Frenkel effect, and tunneling effect. According to the simulation results, the FDC-0.5 wt.% sample has the lowest E-field. Its maximum E-field reduced significantly by 70 82% in comparison to the silicone gel sample, demonstrating exceptional E-field reduction ability throughout a wide temperature range of 20 200°C. According to the Weibull statistical results, the characteristic PDIV of the FDC-0.5 wt.% sample is 13.1 10.3 kV, which is double that of silicone gel at 20 200°C. The findings in this study demonstrate that the proposed FDC bulk material is suitable for insulating MV power modules rated at 10 kV at high temperatures