Electric Arc


Also found in: Dictionary, Thesaurus, Wikipedia.
Related to Electric Arc: Electric arc furnace

electric arc

[i¦lek·trik ′ärk]
(electricity)
A discharge of electricity through a gas, normally characterized by a voltage drop approximately equal to the ionization potential of the gas. Also known as arc.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Arc, Electric

 

(also called voltaic arc), one kind of self-maintaining arc discharge in a gas, in which the discharge phenomena are concentrated in a narrow, brightly glowing column of plasma. If the electrodes are horizontal, the column becomes arc-shaped under the influence of the upward currents of hot gas heated by the discharge.

An electric arc between two carbon electrodes in air was first observed (1802) and described (1803) by the Russian scientist V. V. Petrov and the English scientist H. Davy (1808–09), who called it a voltaic arc. Papers by the Russian scientists N. N. Benardos (welding with carbon electrodes, 1882, and AC welding) and N. G. Slavianov (welding with metal electrodes, 1888–91) were devoted to the development of the theory of the electric arc and the study of problems of its use in industry.

An electric arc can exist in any gas at near-atmospheric and higher pressures. At atmospheric pressure and a current strength of several amperes (amps), the plasma temperature in the column is about 5000°K; at high pressures and current strengths it is up to 12,000°K; and if the column is blasted with a powerful gas flow, the temperature reaches 50,000°K. The temperature distribution for various parts of an electric arc between carbon electrodes with a current of 200 amps is shown in Figure 1.

The magnetic field formed by the current of the electric arc interacts with the current, causing compression (constriction) of the column. With an increase in pressure in the surrounding medium, the current strength in the electric arc increases and the cross section of its column decreases. Near

Figure 1. Temperature distribution in various parts of the column of an electric arc

the electrodes the arc column is constricted even more, forming bright cathode and anode spots on their surfaces. The current density at the arc cathode depends on the cathode material and kind of gas and is usually 104-105 amps/cm2, but under specific conditions it can rise to 107 amps/cm2.

The current-voltage characteristic of an electric arc is a descending curve: a rise in current is accompanied by a drop in voltage between the electrodes.

Electric arcs are used in electrometallurgy (to make pure and refractory metals) and in lighting technology, and particularly extensively in electric welding. In some technical fields (for example, high-voltage technology), it is necessary to combat electric arc phenomena. Switches with various arc quenchers, including air, oil, and elegaz (sulfur hexafluoride) switches, and quenching by magnetic field are used to extinguish arcs that arise when high-voltage circuits are broken.

REFERENCES

Nikitin, V. P. “Russkaia shkola v razvitii elektricheskoi dugovoi svarki.” Avtogennoe delo, 1948, no. 7.
Somerville, J. M. Elektricheskaia duga. Moscow-Leningrad, 1962. (Translated from English.)
Butkevich, G. V. Dugovye protsessy pri kommutatsii elektricheskikh tsepei. Moscow, 1967.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Iron Alternatives--Initially, electric arc furnace (EAF) steelmakers such as Nucor Corp.
Paton Electric Welding Institute of NASU started development of oxide cathodes of electric arc early in 1980s.
His GFG Alliance also has plans to boost capacity utilisation at the electric arc furnaces and rolling mills in Melbourne, Sydney and Newcastle.
In Section 2, complicated dynamical behaviour of the nonlinear AC-fed electric arc furnace model is further investigated.
The site was modernised in the 1950s with the introduction of six electric arc furnaces.
He writes: They are of my father, Kenneth Webster, and a few of his work colleagues at the BSC electric arc plant which shut down in 1980.
The series measures the instantaneous pressure increase inside a continuously closed test chamber resulting from a high-energy electric arc that ignites vapor from a 2-mL sample.
The voltage in the phase with the fault is limited by resistance of the electric arc (See Fig.
Rather than going to China, however, many of the cargoes are heading to other East Asian nations as well as off the Atlantic Coast to European nations with significant electric arc furnace mill capacity.

Full browser ?