Current density and temperature of high-current arcs

DURING INTERRUPTION of high-current arcs in circuit breakers and contactors, the region between the contacts must be converted from an intensely hot conducting medium to a relatively cool insulating medium. Although the cooling of low-current arcs has been explained by means of conduction, free convection, and radiation, extension of these mechanisms to relatively short (2- to 3-inch) high-current arcs accounts for no more than 25% of the total electric energy input. The purpose of this article is to present a theory, physical picture, and supporting data to explain the cooling process in a high-current (10,000- to 20,000 ampere) free arc.