Enhancement of current interruption capability of gto opening switches

The possibility of achieving reliable current interruption of GTO's at ranges much higher than rated in single mode operation was tested. The GTO's tested were the symmetric I.R. 81RDT120M and the asymmetric Marconi DG508SH, with rated 350 A and 1800 A (I/sub TCM/) repetitive peak controllable, current respectively. It is estimated that currents for the two GTO's can be interrupted at triple and 1.3 - fold the rated currents, respectively. Indications of impending turn-off failure are described. Test results with inductive load showed that a high power spike caused a local temperature increase which destroyed the device.