Calculation of Partial Discharge Failure Rate for Power Module by Considering Volume Effect of Silicone Gel

ABSTRACT Power module (PM) is a key device to control electric power in various systems like electric vehicles, railway systems, and HVDC transmissions. Silicone gel is a common encapsulating material for PM and it is known that its insulation performance significantly depends on the stressed volume (volume effect). In this paper, we present the stochastic method for obtaining the partial discharge failure rate of PMs from experimentally measured partial discharge inception electric fields (PDIEs) and E ‐ v plot of PM calculated by electrostatic simulation. The volume effect of PDIEs are measured using fundamental rod‐plane electrodes samples with several stressed volumes. As a result, failure rate of PM is calculated as a reasonably small value. Through the calculation, critical electric field strength and corresponding part of silicone gel for PM insulation is quantitatively understood. By using this method, insulation performance of PM can be calculated without prototype evaluation, so insulation design can be better than before. We also discuss the applications of the method for practical reliability problems.