Step-like shifts in the voltage—Current characteristics of power thyristors and their effect on transient thermal impedance determinations

In the course of determining the transient thermal impedance of power thyristors, step-like shifts are often observed in the temperature-sensitive voltage characteristic used to estimate the virtual junction temperature of the device. This correspondence describes investigations which have shown that these step-like shifts are in fact spontaneous voltage transients which are highly sensitive functions of current and temperature, and which cause small hysteresis effects in the voltage-current characteristics of the device. A simple method for adjusting the temperature sensitive voltage data to correct for such shifts is described; the method yields valid transient thermal impedance determinations in far less time than could be realized without the correction method.