Influence of gate drive and anode circuit conditions on the turn-off performance of GTO thyristors

Measurements of anode current redistribution at turn-off are used to demonstrate the effect of different snubber circuit and gate drive conditions on the behaviour of a 56 mm, 1400 A, 2500 V GTO thyristor. The discussion offers a comprehensive explanation for the differences in device behaviour observed as both the turn-off gain and snubber capacitance are altered. Levels of redistribution are shown to be affected by the choice of snubber capacitance and level of snubber circuit stray inductance. Another important result shows that a low turn-off gain reduces the level of redistribution and thus allows the use of smaller snubber capacitors. Finally, it is concluded that even with continuing advances in device manufacture, a close-coupled anode circuit design and high-performance gate drive are necessary for applications requiring a reduced snubber capacitance