Thermal network model of multichip PP IEGT considering the thermal coupling effects

Press pack IEGTs (PP IEGTs), with the merits of higher reliability and larger current rating, are widely used in AC/DC system, especially in high-voltage direct current (HVDC) power grid. The thermal design, however, remains a crucial topic for the reliable operation of PP IEGTs, and building a comprehensive thermal network and model is an important segment. In general, conventional thermal networks do not include the thermal coupling effects, actually existing in the multichip package, and that would affect the accuracy of junction temperature calculation. For the multichip and multi-layer structure of PP IEGTs, this paper proposes a 3D thermal network model by considering the thermal couplings between chips. The temperature distribution is investigated at given heat power and cooling conditions through numerical simulation, and thermal coupling effects are analyzed with a thermal impedance matrix. With the coupling impedances of PP IEGT, building a compact RC network model for the junction temperature identification. Results show that the proposed model offers improved accuracy in predicting the transient temperature of PP IEGT. Moreover, the study shows that the thermal coupling effect is seriously existent within the package, especially the heat accumulates at the centric position, which is a real menace for device reliability.