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

Abstract

The objective of this paper is to measure the effect of an axial magnetic field (AMF) BAMF 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 BAMF ranging from 0 to 110 mT 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 JPeakArea I decreased with increasing BAMF following a power law. For BAMF of 0–110 mT and IARC of 4–14 kA, JPeakArea I = (2.2 IARC + 0.069 IARC2) BAMF−0.22, where JPeakArea I is in A/mm2, BAMF is in mT, and IARC is in kA. Moreover, the current distribution was uneven in the three peripheral areas.

Effect of six pure metals cathode on constricted characteristics of high-current vacuum arcs subject to axial magnetic field

“…As shown in figure 6, under the cathode of Cu, W, Mo, Fe, Cr, Al, respectively, the average anode current densities in the central areas ranged from 12.5 A mm −2 to 20.0 A mm −2 , at the same transient current of 14.1 kA. Comparing to the previous results of current density [18,19], the determining process on current and current density distributions in high-current vacuum arcs should be reproduced and the quantitatively experimental results should be reliable.…”

“…In the previous researches with the contacts material of CuCr25 and the cup-shaped AMF cathode [18], the current density in the central areas was 20 A mm −2 in diffuse arc mode with the transient current of 14.1 kA. At the uniform AMF of 74 mT and the contacts material of CuCr25 [19], the current density in the central areas was 10.6 A mm −2 with the transient current of 14.1 kA. As shown in figure 6, under the cathode of Cu, W, Mo, Fe, Cr, Al, respectively, the average anode current densities in the central areas ranged from 12.5 A mm −2 to 20.0 A mm −2 , at the same transient current of 14.1 kA.…”

“…The constriction of the vacuum arc is closely related to the distribution of the cathode spots and the formation of the anode spot [1][2][3]. The axial magnetic of the current density in vacuum arcs [13][14][15][16][17][18][19]. Sherman et al [13], Mitchell [14] and Drouet et al [15] tried to determined the arc current distribution experimentally, with the method of a magnetic probe, 7-element anode contact and a multiring anode contact, respectively.…”

“…Based on ring-shaped electrode, Wang et al [17] experimentally investigated the distribution of the cathode current density in the vacuum arcs. Ma et al [18,19] measured the anode current density distribution for various vacuum arc modes and investigated the effect of AMF on the anode current density by a split-anode contact. The relationship of the anode spot formation threshold current dependent on the AMF was determined by Kong et al [20,21].…”

Dynamic Arc Current Distribution of Parallel Vacuum Arcs Subjected to Bipolar Axial Magnetic Field

“…In [11], linear current distribution in a moving arc root along seven directions was measured though multiple split cathode with different slit angle setup. By means of 4-split anode electrode and Helmholtz coils, effect of axial magnetic field on current density in the central anode area was obtained [12]. Besides, contributions related to arc current based on numerical calculation method were reported.…”