Large Electric-Arc Furnaces-- Performance and Power Supply

In March l940, a 25-ton Heroult 3-phase electric arc furnace using a 10,000-kva 1.5 volts (115-volt base) for the 66-kv system with fluctuations from 3 per hour up to 15 per minute. Precautions were taken in the design of the furnace transformer to include separate reactance to reduce the load swings. Subsequently, it was found that this additional reactance was not eneded and it was removed, thereby improving the operation of the furnace. The load swings and accompaning voltage changes, after disconnecting the reactance, due to the operation of the first furnace, slightly exceeded the Duquesne Light Company standards. However, no complaints have been received from adjacent customers nor have any difficulties arisen from excessive operation of 4-kv distribution regulators, operation of the power stations, or interconnections.