Covers electrical characteristics and mechanical features of 3-phase, 60-cycle, 2-winding, mineral-oil-immersed indoor transformers rated 250 to 35,000 kva (kilovolt-amperes), inclusive high voltage 2,400 to 34,400 volts, inclusive for electric power to direct arc ferrous-melting furnaces. For all other characteristics and definitions, see American Standards' for Distribution , Power, and Regulating Transformers, and Shunt reactors, C57.12 Series.