In high power applications, thermal considerations are fundamental. The voltage and current capabilities of today’s semiconductors increase steadily and so, too, do their power dissipations, reaching several kW per package. Generally, thermal modelling is used to design the cooling system of a power converter and to obtain an accurate prediction of the cooling system’s performance. In so doing, it is important to consider the coupling between cooling water, junction temperature and dissipated power. This paper presents a comprehensive modelling method, based on a 3D thermal model, which takes into account the electric and fluidic interactions with the temperature field in a press-pack device. The modelling method is applied to an IGCT (Integrated Gate-Commutated Thyristor) working in a high power chopper. Internal temperature measurements in switching, transient and steady-state modes are performed. Measurement results are used to fit the 3D model by adjusting the value of the thermal contact resistances between the different parts of the IGCT device. Thus, the differences between measurement and modelling result are less than 10% both in transient and steadystate modes. Finally, the model is used to determine the influence of water-flow direction on the IGCT junction temperature. Furthermore, the model is used to estimate IGCT losses and junction temperature fluctuations in the case of a DC arc furnace power supply.
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