On a certain disadvantageous mode of the arc between cup‐shaped contacts during high‐current interruption in vacuum

The article presents research results of discharge development and arc modes of high‐current vacuum arc between cup contacts with slots to generate a transverse magnetic field (i. e. contrate contacts). The peak value of the applied AC arc current half‐wave ranged from a few kA to 27 kA. Photographs of the arc were taken with a high‐speed framing camera at 10 000 frames/s. It was found that the arc between cup‐shaped contacts behave in a similar way in the following two cases: if the electrodes are separated shortly after the onset of the main current, and if the arc is created at a fixed contact gap. It was shown that, for both cases, there is a tendency to locate the stationary anode spot inside the cup and the arising stationary constricted arc mode, which is disadvantageous in terms of arc extinction.