Anode Current Distribution in a Moving Arc

Abstract

Two new measuring techniques are discussed. They give, respectively, the distributions of the arc current in the directions parallel and transverse to the arc motion. They are applied to measurements on an arc, 1.6 mm in length, burning at up to 700 A, in air at atmospheric pressure, between 2 parallel copper electrodes and driven, at up to 200 ms" 1 , by a transverse magnetic field. The measured distribution profiles are nonsymmetrical in both directions. The current density at the arc foot is much larger than previously reported for the arc column. The transverse profile is characterized by a high-current core with 2 low-current wings.

The Estimation of the Current-Density Distribution in a Moving Arc Root Using the ART Algorithm

“…This also means that the double vortex, particularly in the arc column that is close to the cathode surface, affects the local temperature distribution and electrical conductivity and subsequently affects the current-density distribution of the arc root. In addition, it is clear that J(x, y) is asymmetrical with respect to the directions of either the transverse magnetic field or the arc motion, and this is well consistent with the deduction made by Drouet [6].…”

“…The peak value of J(x, y) obviously tends toward its fore part. A similar current-density distribution exists in the cross section of a transverse magnetic field driving the arc column because of the presence of the double vortex [6], [17]. This enlightens us to attempt to make the following interpretations for the appearance of the J(x, y) in a moving arc root:…”

“…7. A smaller value of 5 × 10 8 A/m 2 was evaluated at the anode surface by Drouet et al for a 750-A moving arc in different arc conditions [6]. There are two important reasons for it.…”

“…The values of V x were derived from the records of a high-speed camera. These results were synthesized according to (4)- (6), and then, the final arc linear current distribution in seven directions can be obtained. Three of those are shown in Fig.…”

“…However, these methods have shortcomings and limitations [3], [4], and it is greatly difficult to apply them to evaluate the current-density distribution of an arc root. With regard to direct methods, Drouet and his cooperators adopted a slit-cavity electrode in which they embedded Manuscript a voltage transducer to measure the current distribution in the direction of arc-root motion on anode surfaces [5], [6]. However, the results obtained previously are only linear current distributions in the directions parallel and transverse to the arc motion.…”