The current-carrying capacity of solid bare copper and aluminium conductors

The current-carrying capacity of bare copper and aluminum conductors is limited by the heating effects produced by the current. The dissipation of this heat is a function of the temperature elevation above the surrounding air, the size of the conductor, and the intrinsic condition of the surface. A cooling-curve method is described which was used in determining the coefficient of heat emissivity for a series of small sample lengths of round and flat copper and aluminium conductors of various sizes and surface conditions. This was checked by the direct electrical heating of longer lengths, which showed the two methods to be in close agreement. Tables for the current-carrying capacity of copper and aluminium busbars have been deduced from the constants obtained and are given in the paper.