Power semiconductors-a new method for predicting the on-state characteristic and temperature rise during multi-cycle fault currents

A concept, test procedure, and evaluation method are described for determining the on-state voltage of thyristors (or diodes) over a very wide temperature range to the limit of normal behavior. The difficulty that the temperature dependence is not constant has been overcome, and a mathematical relationship representative of this dependence as a continuously changing variable, a function of both current and temperature, is derived from the analysis of data. Measurement involves a series of single-cycle test shots at the fault current level or I _TSM with varying starting temperatures ranging from 25° to 150°C. Combining mathematical representations of the recorded voltage and current traces with a preestablished thermal model, the junction temperature profile or excursion which occurs simultaneously is calculated. The proposed approach is applied to a 5000 V class 100 mm thyristor