GB863312A - Improvements in and relating to a magnet system - Google Patents

Abstract

863,312. Automatic circuit-breakers. FABRIE KVAN ELECTRISCHE APPARATEN VOORHEEN F. HAZEMEIJER & CO. N.V. June 21, 1957 [Dec. 15, 1956], No. 19610/57. Class 38 (5). [Also in Group XXXV] A magnet system, especially suitable for tripping a circuit-breaker, comprises a main magnetic circuit including a permanent magnet, two ferromagnetic cores extending from the poles of the permanent magnet to two polepieces to which an armature is normally attracted, and an auxiliary magnetic circuit including an H-shaped member of ferromagnetic material located between the two cores and spaced therefrom to act as a shunt across the main magnetic circuit so that upon excitation of the auxiliary circuit the attraction of the armature is reduced sufficiently to release it. The auxiliary circuit may be excited by D.C. or single- or three-phase A.C. A three-phase arrangement comprises two permanent magnets 1 and 2 bridged by a ferromagnetic member 21, two solid cores 4 and 5 extending from the magnets 1 and 2, and two laminated extension cores 6 and 7 terminating in pole faces 15 and 16 to which the armature 3 is attracted against the action of a releasing spring on the armature spindle 17. An H-shaped ferromagnetic core 8 is located between the cores 6 and 7, and three coils 13 or 14 connected to a three-phase supply with one phase reversed provide auxiliary excitation, the connections being such that the direction of flux is as shown by the arrows to divert the main flux across the H-shaped core and thus reduce that through the armature, this effect being independent of the instantaneous direction of A.C. The cores are embedded in synthetic resin, preferably by moulding in two sections which are subsequently joined by a filling-piece 29, all abutting magnetic faces being ground and polished. Fillers may be incorporated in the resin so that its thermal expansion characteristic will match that of the cores. Protective cut-out arrangement (Fig. 4).-To trip a circuit-breaker the coils 13 and 14 may be energized by current transformers Tr upon operation of a relay Mb which opens contact c. Release of the armature under the action of spring Uv lifts arm Uh to effect rotation of a D-shaft which operates the breaker tripping mechanism.