Effect of an axial magnetic field and arc current on the anode current density in diffuse vacuum arcs

摘要

The objective of this paper is to measure the effect of an axial magnetic field (AMF) B-AMF and arc current on the anode current density in diffuse vacuum arcs. The experimental geometry included a split anode and a butt-type cathode, both with a diameter of 60 mm. The anode surface was divided into a central area and three symmetrically disposed peripheral annular areas. The central area of the split anode had a diameter of 20 mm. The contact material was CuCr25 (25% Cr). The arc current IARC ranged from 4 to 14 kA (rms) at 50 Hz. The opening velocity was 2.4 m/s. The currents of the four areas on the anode contact were measured using four Rogowski coils situated outside the vacuum chamber. An external uniform AMF B-AMF ranging from 0 to 110mT was applied during the experiment. The observed arc modes were recorded by a high-speed charge-coupled device video camera. The experimental results quantitatively reveal that the current density distribution on the anode surface in the diffuse arc mode was not uniform but concentrated in the central area. The current density in the central anode area at the current peak J(Area I)(Peak) decreased with increasing B-AMF following a power law. For B-AMF of 0-110mT and I-ARC of 4-14 kA, J(Area I)(Peak) = (2.2 I-ARC + 0.069 I-ARC(2)) B-AMF -0.22, where J(Area I)(Peak) is in A/mm(2), B-AMF is in mT, and I-ARC is in kA. Moreover, the current distribution was uneven in the three peripheral areas. Published by AIP Publishing.