Determination of Thermal Cross-Coupling Effects in Multi-Device Power Electronic Modules

A dynamic thermal model is developed for a 350A half bridge IGBT module and cooler which includes the effects of thermal cross-coupling between the various semiconductor elements. The parameters for the model are extracted from measurements of the transient thermal impedance from junction to ambient. A matrix representation of the model is developed which in turn is implemented into a working model in PSpice by use of a multi-term R-C network. Simulation results show that the cross-coupling effects during load power cycling are not negligible and are dependent on the load power frequency. It is concluded that typical thermal models derived from manufacturers´ data may significantly underestimate junction temperature elevation in multi-device power modules.