GB841866A

GB841866A - Improvements in and relating to electromagnetic relays

Info

Publication number: GB841866A
Application number: GB1754955A
Authority: GB
Inventors: John Walter Freeman Smith
Original assignee: English Electric Co Ltd
Current assignee: English Electric Co Ltd
Priority date: 1955-06-17
Filing date: 1955-06-17
Publication date: 1960-07-20
Also published as: FR1167687A; DE1029077B

Abstract

841,866. Electromagnetic relays; protective cut-out arrangements. ENGLISH ELECTRIC CO. Ltd. June 15, 1956 [June 17, 1955], No. 17549/55. Class 38 (5). The core 20 of a relay, Fig. 2, is split to form a local closed flux path 20a, 20b saturated by a control coil 22. The armature 21 controlling contacts 24 is operated by flux produced by the operating coil 23, the current in the coil 23 necessary to overcome the opening bias of the armature being dependent upon the reluctance of the core 20 which may be varied by variation of the current in coil 22 to alter the degree of saturation of the closed path 20a, 20b. The relay may be employed in a protective system (Fig. 1, not shown), in which the coil 22 is energized in accordance with the voltage of the protected line and coil 23 in accordance with the current so that should the line voltage drop the reduced reluctance of the relay core permits the coil 23 to operate the contacts and trip a circuit-breaker. In an actual relay construction, Fig. 3, a rectangular magnet frame 35 is saturated by the series-connected control coils 36, 37 and the operating winding 38 surrounds these coils. The flux path for the winding 38 is completed by an arm 33 and a spring-biased armature 39 pivoted thereto, an arm 41 on the armature closing contacts 31, 32 when the armature is attracted to the frame 35. In a modification of Fig. 2 (Fig. 4 (c), not shown), the closed flux circuit 20a, 20b is formed in the lower horizontal limb of the core. The characteristic of the relay may be varied by providing additional coils on the core limb having the control coil and connecting these coils in series with the operating winding. In an alternative application of the relay shown in Fig. 2, both windings 22, 23 are supplied from the same variable voltage source, but winding 23 is supplied through a capacitor-resistor circuit whereby the relay does not operate until after a predetermined time delay which is independent of the voltage.