Automatic protection for stuffing-box type drainage pumps - has current/voltage converter between one phase of supply and motor, whose output goes to two comparator systems, thence to relay

摘要

The motor for a circulating pump has a two-level system and a time relay whose set of contacts is joined to an AC source. There is a current/voltage converter (1) in series between the supply to one motor phase and the input terminal of the contact set (2) for the protection system. The output of the converter is also joined to the input of a comparator system (5) for the peak motor current when idling and the input of another comparator system (6) for the peak overload current. The outputs of both systems are processed (7) into signals controlling a relay (9).