The influence of circuit parameters and contact materials on the reignition of high frequency vacuum arcs

The extinction or reignition of high-frequency transients plays an important role in the generation of voltage surges. Investigations with currents of several hundred amperes peak and current frequencies from 100 kHz up to 1 MHz were made to examine the reignition behavior of short vacuum gaps using different contact materials. The experiments were carried out in an UHV (ultrahigh vacuum) test chamber connected to an LC test circuit with voltages in the 10-kV range. The statistical distribution of the reignition voltage after current zero of HF vacuum arcs yields two probable reignition mechanisms, the cold gap behavior and the plasma-influenced reignition. The reignition tendency increases with rising di/dt and rising current frequency. The reignition voltages of the examined contact materials increase in the sequence: OFHC Cu, Cr, Cu/Cr 75/25