Performance of a corona-stabilised switch activated by fast-rising trigger pulses

Abstract

Plasma closing switches used in pulsed-power applications have traditionally been insulated with sulphur hexafluoride (SF6) due to its high dielectric strength. The global warming potential of SF6, however, is estimated to be 23900 times greater than that of CO2. The present study details tests conducted in order to replace SF6 with air as the switching medium within an existing corona-stabilised switch, the main goal being to extend the triggering range by deploying a fast-rising (~40 ns) trigger pulse. Delay times were measured and jitter calculated at a range of pressures, for different triggering regimes. The most stable performance was found with a negative-polarity dc voltage across the main electrodes, and a positive-polarity trigger voltage. With this triggering regime, the average delay time to breakdown was ~300 ns over a 2-bar pressure range. The minimum calculated jitter was 5 ns. When the switch was charged with a positive dc voltage and the trigger pulse was of negative polarity, the triggering range was extended by up to 7 kV compared to the triggering regime previously used (μs pulse).