GB1236916A - Improvements relating to electro-magnetic tripping devices - Google Patents

Abstract

1,236,916. Electromagnetically tripped switches. A. REYROLLE & CO. Ltd. 3 Sept., 1968 [5 June, 1967], No. 25856/67. Heading H1N. A polarized holding electromagnet having a spring-biased armature releasable to act on a circuit-breaker trip mechanism, has a yoke structure of symmetrical rectangular form affording duplicated magnetic circuits, one on either side of a central elongated core member which is common to both magnetic circuits and on which two spaced series trip coils are wound. The armature 30 is rectilinearly movable and is ' held, by flux from permanent magnets 19, 20, in engagement with faces 26 of two rectangular section polepieces 21 to bridge air gaps 29 in the duplicated magnetic circuits on either side of the core 13 which also houses the armature biasing spring 35. Air gaps between the polepieces 21 and magnetic end pieces 16 are set by non-magnetic shims 24. The housing 10 is dust-proofed by a diaphragm 41 secured around a guide sleeve 37 for the extension spindle 31, 36 of the armature which has a spring-loaded button 40 to allow for overtravel in resetting of the trip mechanism (not shown). The permanent magnets may be magnetized after assembly in the housing 10 of the electromagnet by temporarily connecting the coils 14, 15 in parallel and in opposition (Fig. 5, not shown). In an alternative arrangement (Figs. 6 to 8, not shown) soft iron shunts are provided so as to prevent demagnetization of the permanent magnets during an initial current surge in the coils 14, 15.