Effect of contact material on the extinction of vacuum arcs under line frequency and high frequency conditions

In two different test arrangements the influence of different contact materials (Cu/Cr and Cu/Cr with additives of Zn, Sb, and Li₂O) on reignition or extinction of vacuum arcs was studied. The following line frequency conditions were achieved in a synthetic Weil-Dobke circuit: a transient recovery voltage (TRV) of 36 kV, and currents of 800-4800 A, 50 Hz. High-frequency (HF) currents were generated by means of all L-C circuit, with amplitudes of several hundred amperes and frequencies in the range of several hundred Kilohertz. The reignition voltage at the HF current zeros and its statistical distribution are evaluated. Cu/Cr 75/25 shows the highest values, in agreement with the tendency at 50 Hz. As at line frequency, the additives reduce the reignition voltage, and hence, increase the reignition tendency. Cu/Cr with higher Cr content has a smaller breaking capacity