Voltage/current characteristics of high-current vacuum arc at a small gap length

Measurements of are voltage for semiwave currents of the amplitude up to 13 kA and frequencies 0.9 kHz and 6.0 kHz were done for CuCr electrodes whose separtion was 2 mm. The obtained data were used to determine voltage/current and voltage-time characteristics of high-current vacuum are. They enabled to state as: a) The shape and values of are voltage during a sinusoidal current semiwave flow depend on the current amplitude and frequency. As the current amplitude increases the are voltage rises, and its shape changes from relatively low and quiet to high with considerable fluctuations of high frequency and amplitude (HAF). b) Are voltage at a given current instantaneous value i(a1) depends on the current waveform before reaching i(a1). The are voltage beyond the range of HAF occurrence, at the same instantaneous value of the sinusoidal current, is higher during the current increase than during its decrease and higher for higher current frequency. c) Mean are voltage and current value at the moment of HAF onset, rise with the increase of current peak and frequency. This article presents qualitative correlations between the measured are voltage and an expected discharge mode in the intercontact gap.