Empirical study on humidity conditions inside of power modules under varying external conditions

Abstract:
During the last years applications with power modules operating under harsh environmental conditions have gained increasing importance. Extreme combinations of environmental conditions especially at weak load can lead to agglomeration of humidity inside inverters that may even cause condensation. Examples are found in wind power applications during long term off the grid mode or train applications when passing tunnels causing a rapid change in ambient conditions. It is necessary to understand the physical processes inside power modules including the direct chip environment to apply life time modelling to these conditions. Furthermore, an empirical study is needed -that can be applied- to check the applicability of the hygro-thermal simulations of complex converter designs as mentioned by Bayerer et al.. The present work establishes experimental techniques for in-situ measurements of humidity and condensation inside power modules. First results on the dependence of both parameters on transient ambient conditions are presented.