Limit Operation Regimes of Selected Power Semiconductor Elements

Operation regimes of modern power semiconductor devices (such as IGCT thyristors or IGBT transistors) are characterized by switching high currents of the order of kA at the voltage level of several kV. Although their internal and eventual contact resistances are very low, the Joule losses in them reach quite high values and corresponding heat may lead to unacceptable (local or global) temperature rise. The paper represents an introductory study in the area and deals with partial mathematical and computer modeling of the temperature rise of an axisymmetric device during its operation in several regimes differing by nominal current and frequency of switching. Modeled is, however, only the nonstationary temperature field, while the distribution of the specific Joule losses was found experimentally. The convective heat transfer coefficient necessary for formulation of the boundary condition of the third kind is calculated approximately from velocity of the cooling air. The methodology is illustrated on an example of a real IGCT device. Selected results are compared with measurements