GB719917A - Polarised electro-magnetic tripping device for an electric switch - Google Patents

Abstract

719,917. Electrically tripped switches. AKT.- GES., BROWN, BOVERI & CIE. Dec. 4, 1952 [Dec. 29, 1951], No. 30766/52. Class 38(5) In a polarized electromagnetic tripping device, an armature is rotated in one direction by reverse current and in the other direction by forward excess current, rotation in either direction producing tripping by means of linkage systems such that a tripping catch is always moved in the same direction. In the Figure, a polarizing coil 2 sets up a constant magnetic field in the armature 5 and magnetic yoke 1, as indicated by full lines, and the current in bus-bars 3, i.e. the protected circuit, when flowing in one direction sets up the magnetic fields indicated by dotted lines. When the latter current is sufficient, the resultant field in the lower left hand pole piece and the upper right hand pole piece is able to rotate the armature 5 in an anticlockwise direction and by means of the left-hand linkage 6, 7, 10, rotate a catch 12, to release a switch lever 13. Should the current in the bus-bars 3 reverse, the armature is turned in a clockwise direction and through the righthand linkage 6, 7, 10<SP>1</SP> rotates the catch 12. The connections of the linkages to the armature 5 and catch 12 are such that when the armature rotates in one direction to move one linkage no movement is transmitted to the other linkage. The current settings are determined by setting the initial tensions of springs 8 which bias the links 7 against stops 9, the stops being adjustable so that the initial position of the armature may be set to permit response to low reverse currents.