A study of voltage transients in arc-furnace circuits

IN the history of the operation of are furnaces for melting steel there have been occasional evidences of overvoltage transients. These evidences have been chiefly electrical breakdown of equipment associated with are furnaces which were not attributable to causes other than abnormally high voltage. In the last three years with the increased number of are-furnace installations and the increased seriousness of interruptions to production, a considerable amount of attention has been focused on this problem. This paper presents the results of voltage surge measurements made on two furnace installations in an attempt to accumulate accurate data as to the magnitude of such overvoltages and the factors which influence them. Before entering into a discussion of voltage surges, however, it seems advisable to review the component electrical parts of an arc-furnace circuit and the procedure followed in its operation.