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

Measurements of arc 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 arc. They enabled to state as:

1. The shape and values of arc voltage during a sinusoidal current semiwave flow depend on the current amplitude and frequency. As the current amplitude increases the arc voltage rises, and its shape changes from relatively low and quiet to high with considerable fluctuations of high frequency and amplitude (HAF).
2. Arc voltage at a given current instantaneous valuei _a1 depends on the current waveform before reachingi _a1 . The arc 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.
3. Mean arc 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 arc voltage and an expected discharge mode in the intercontact gap.