The use of thyristors as main switches in EML applications

The authors studied the application of conventional, bipolar thyristors with different finger gate structures as current switches in electromagnetic launchers (EMLs). The experiments showed that the bipolar thyristors have to have a fine structured gate to be able to switch a high current within a short time (high dI/dt). The authors succeeded in switching currents of 90 kA with a maximum dI/dt of 550 A/ mu s and a blocking voltage up to 6.5 kV within 0.26 ms. Results obtained with serial and parallel configurations of conventional thyristors are also reported. If steps are taken to distribute the voltage equally, the devices in series work well. In parallel configurations an equal current distribution can be realized by giving each thyristor its own current source. With such a configuration of four parallel thyristors, it was possible to achieve switching currents of 160 kA within 0.25 ms. The blocking voltage was 4.2 kV and dI/dt was 250 A/ mu s.>