Transient decay of current through paralleled mercury-arc and silicon rectifiers

THE ADVENT of silicon semiconductor rectifier applications to large potlines has brought about application problems heretofore not significant. Many of the users of large amounts of d-c power wish to try a large power silicon rectifier in actual service before the purchase of a complete potline. Since the greater majority of the existing potlines have mercury-arc rectifiers providing the d-c power, it is only natural to put a silicon rectifier on a potline in parallel with the mercury-arc rectifiers. Fig. 1 is a single-line diagram of a modern electrochemical potline. The normal method of de-energizing the line is to trip the master a-c circuit breaker feeding all units. The problem of magnitude of potline decay current which must be handled by a single silicon rectifier in parallel with several mercury-arc rectifiers under these conditions requires analysis.