The determination of the electrical characteristics of an arc furnace

The paper describes three different methods for the determination of the electrical characteristics of arc furnaces. A comparison is made between the three methods by applying each in turn for the determination of the electrical characteristics of a 10cwt Héroult-type 3-phase arc furnace. In the first method the characteristics are obtained directly from observations on the furnace during normal operation and under short-circuit conditions; in the second method the furnace curves are calculated by using an equivalent circuit for the 3-phase arc furnace; the third and most simple method treats the furnace as a balanced 3-phase load and utilizes a current-locus diagram to calculate operating points on the characteristics. For the 10cwt furnace the simple locus-diagram treatment gave results of sufficient accuracy for all practical purposes, and the characteristics show that the furnace is most efficient, electrically, when operated on the highest voltage tapping.