Abstract :
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.
