The application of thyristors as main switches in railguns

ISL-EMA railguns are driven by capacitors and equipped with spark gaps as main switches and semiconducting diodes as crowbar switches. We report on investigations to replace the spark gaps by thyristors. First tests with the application of phase-controlled thyristors showed that the decices should have a fine structured gate at their disposal to enable the high current rate typical for pulsed power applications. Because of this, experiments were made with a pulse power thyristor developed by ABB and with a modified fast switching thyristor. The pulse power thyristor has the gate structure of a GTO device, but in contrast to a GTO, it is not possible to switch it off. Furthermore a modified fast switching thyristor was investigated due to pulse power applications. The device has a blocking voltage of 3 kV and, in contrast to a normal fast switching thyristor, it is not irradiated. By this step the charge carrier lifetime can be increased.