GB389104A - Improvements in or relating to electromagnetic relays - Google Patents

Abstract

389,104. Protective cut-out arrangements. RHEINISCH-WESTF€LISCHES ELEKTRIZITATS - WERK AKT. - GES., Essen, Germany. Aug. 31, 1931, No. 24444. Convention date, Aug. 29, 19,30. Addition to 309,182, [Class 38 (v), Electric switches &c.]. [Class 38 (v).] For carrying into effect the protective arrangement described in the parent Specification the relay employed has a coil with a plurality of windings and an armature which is movably mounted between the poles of a permanent magnet and which is moved to release a switch as soon as the sum of the magnetic effects of the windings of the coil differs from zero owing to one of the current-carrying conductors being touched. As shown in Fig. 1, coils c, d in the circuits of the conductors e, f are wound in opposition on an H-armature b pivotally suspended between the poles of a permanent magnet a. Normally the effects of the coils neutralize each other and the armature is retained as shown in the central position with an insulated arm n resting against a stop g, but when the currents in the conductors e, f are unequal the resultant magnetic force of the coils b, c magnetize the core so that it swings and engages by a projection i a tripping lever k of a spring-controlled switch in the circuit e; f. If used on A.C. and the force on the armature at the moment is in a direction pressing the arm n against the stop g, tripping is not initiated until the succeeding half-cycle. More than one pair of opposing coils may be mounted on the armature b. In a modified arrangement, Fig. 3, for a three-phase circuit e, f, t a single coil o fed through the secondary p of a summation transformer v is mounted without a core between auxiliary polepieces of a permanent magnet a. An armature b<2> attached to an arm extending from the coil O is mounted between the main polepieces N, S so that as soon as the tripping movement is initiated the armature b<2> is attracted strongly to the polepiece N. A further form of relay (Fig. 2, not shown) may, alternatively, be employed, of the type comprising a movable magnetic core disposed within a stationery coil consisting of opposing windings in series with the current-carrying conductors, the core extending between the poles of a permanent magnet and being arranged to operate tripping mechanism in the manner previously described.