The current pulse ratings of thyristors

This paper describes how the current pulse ratings of thyristors during turn-on spreading can be obtained from the maximum allowable junction temperature based on time-to-failure using a combination of analytical and experimental methods. The instantaneous junction temperature rise of a thyristor is analyzed with the aid of a digital computer. In the calculation of temperature rise, the transient thermal impedance during turn-on spreading is considered. Analyzed results agree with the values obtained directly by an infrared detector. In order to estimate the maximum allowable junction temperature based on time-to-failure, "step-stress capability tests" were conducted. In many cases, it was found that there were modes of both catastrophic and degradation failure. The maximum allowable junction temperature was estimated for the nonrepetitive and repetitive current pulse ratings.