Anode-circuit-breaker design and performance criteria

THE rapidly expanding use of mercury-arc rectifiers, both as to total installed capacity and the relatively large number of units operating in parallel, emphasizes the importance of suitable switch-gear to provide over-all satisfactory rectifier operation. The necessity for such switch-gear, particularly for a high-speed air circuit breaker in the rectifier anode circuit, has been outlined in previous papers before the Institute.^1,2 During the past several years, considerable progress has been made in the reduction of arc-backs in power rectifiers. Anode circuit breakers, although subject to less frequent duty as a result of this progress, are required to operate at higher voltages and interrupt greater arc-back currents as indicated by recorded rates of rise of current in excess of 11,000,000 amperes per second. At this rate of rise in a large 650-volt (d-c) rectifier installation, the anode-breaker interrupting duty is equivalent to that of the first phase to clear a 130,000-kva fault in a three-phase 1,400-volt a-c system.