公开(公告)号：US3573552A

公开(公告)日：1971-04-06

申请号：US3573552D

申请日：1969-03-27

Applicant: ASEA AB

Inventor： FORFOD THORLEIF

IPC: H02H3/28 ,  H02H3/16

CPC classification number: H02H3/283

Abstract: A relay device operating in response to abnormal conditions in a line includes an arrangement for deriving from the line a current proportional to the current in the line. One terminal of this current deriving device is connected to the midpoint of a pair of rectifiers connected in series. The other terminal is connected to the midpoint between resistances of equal value connected in series with the pair of rectifiers. In the connection between the midpoint of the resistances and the terminal of the current deriving device is arranged the primary of a transformer. The secondary of this transformer through a full-wave rectifier feeds the relay in parallel with a resistance. The arrangement is such that the relay is fed with the difference between the voltage across the latter resistance and the voltage across the two equal resistances.