Electronic power-converter protection — I: An AIEE committee report

POWER RECTIFIERS of the mercury-pool type must be provided with protection against both overloads and short circuits external to the unit and arc-backs within the unit. Overloads exceeding rated values may occur as the result of unusual conditions in the load circuit, outage of parallel units supplying a common load, or service requirements in excess of installed capacity. In any case, the operation of the rectifier on overload is the same as at rated loads except that the commutating angle increases with increasing load current. This increases the conducting period of the tubes, modifies the anode current and voltage waves, and so changes the duty on the tubes. It also causes the output voltage of the rectifier to drop as the load current is increased.