Partial Discharge Investigation in an Air-Filled Cavity inside Solid Dielectric Under Low-Pressure Conditions using Finite-Element Analysis

The electrification trend in the aviation industry is expected to accelerate. The incentives to this trend include but are not limited to the lower operating cost, lower CO2 emission, and higher fault tolerability of more and all electric aircraft than conventional aircraft. However, the wide bandgap (WBG)-based power conversion systems – despite their superior characteristics such as higher switching frequency/slew rate, higher efficiency, and smaller form factor – are susceptible to partial discharges (PDs). The vulnerability of the insulation system in these devices even exacerbates at higher altitudes due to the lower PD inception voltage, meaning that the discharge ignites sooner than expected. This paper puts forth the modeling of the internal PDs in the insulation systems of the WBG power module using Finite Element Analysis (FEA). The modeling is carried out in COMSOL Multiphysics® and tested on a high power-density IGBT module for two cases where the module operates at (1) sea level (a normal condition) and (2) altitude of 18000 ft. (a low-pressure condition). The results of these cases are thoroughly compared and discussed.