A fast circuit breaker

DURING the past few years the rapid expansion of mercury-arc rectifier installations at 600 volts d-c, both as to the total kilowatts installed and the relatively large number of units operated in parallel, has emphasized the importance of switchgear in providing suitable rectifier operation. In the event of a backfire, the rates of current rise through a rectifier and its transformer windings lie, in general, between three million and six million amperes per second. With large installations, such as shown in Figure 1 where 60 units of 5,000 amperes each are operated in parallel, the ceiling value of these currents is far above a figure which could be tolerated both from the standpoint of continuity of operation and safety to equipment.