Assessment of Catastrophic Failure for Phase Control Thyristors in AC Pulsed Applications

This article presents a theoretical development, supported by experimental results, which is useful for the evaluation of the ride through capability of phase control thyristors that should operate under high multicycle ac, power frequency current surges with different amplitudes between cycles. Despite being commonly found in the field of metals industry applications, this is not a standard data sheet test condition that can be readily used to predict if the device can handle a given surge profile. The present work is devoted to contributing to the fulfillment of this gap. A recursive, discrete-time method is used for the calculation of instantaneous virtual junction temperature of the devices tested. Such method is advantageous over the traditional equivalent power pulse technique since for any given time step only the immediately previous calculation is needed instead of the overall series. It is shown that the results obtained with these two methods are practically identical. Besides, a complete study based on a commercial power semiconductor device is given along with experimental results that support the application of the assessment method developed.