Development and Current–Voltage Characteristic of Arc on AMF Contacts at Different Opening Speeds

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This article presents the results of the investigation of high-current vacuum arcs (HCVAs) on axial magnetic field (AMF) contacts at an average opening speed of 2 m/s and the comparison of the obtained results with similar results received earlier at a lower average opening speed of 1 m/s. We compared the voltage oscillograms and the current-voltage characteristics (CVCs), as well as the arc development process of the discharges at different opening speeds. The discharge was ignited by opening the contacts in a demountable vacuum chamber and was fed with the half-sine current pulse of 10 ms in duration. For analyzing the arc development processes, high-speed video recording of the arc column and the cathode surface was conducted throughout the entire current pulse. We discovered that the process looks similar for both the investigated contact speeds: a discharge is initiated at one or more points and covers the entire contact surface in a few milliseconds. Only quantitative differences are observed due to a higher arc voltage and, accordingly, energy input at a higher speed of contact movement. The CVC of the developed arc in both cases turned out to be linear in a wide range of currents. The analysis of the CVC showed that, in the developed arc, the ratio of the resistance of the column to its length does not depend on the length of the gap and the opening speed of the contacts. Thus, we can assume that the plasma parameters in the column change little with an increase in the current and in the opening speed of contacts. This assumption is supported by the results of a discussion of the literature on the CVC of HCVAs.