Optical triggering of 4H-SiC thyristors (18 kV class) to high currents in purely inductive load circuit

Abstract

Optical switch-on of a very high voltage (18 kV class) 4H-SiC thyristor with an amplification step (pilot thyristor) to the current Imax = 1225 A is demonstrated using a purely inductive load and a calibrated air transformer. Increasing the inductance of the transformer primary winding slows down the turn on process. However, the inductance has little effect during the initial stage of the switch-on process when the voltage drop on the thyristor and its internal resistance is high. The results show that a further switch-on current increase can be only achieved by introducing additional amplification steps in the pilot thyristor.