GB496415A - Improvements in and relating to remote-control switches for alternating currents - Google Patents

Abstract

496,415. Electromagnetic switches; arc-rupturing. BRITISH THOMSON-HOUSTON CO., Ltd. (Allgemeine Elektricitats- Ges.) July 7, 1937, No. 18930. [Class 38 (v)] In an electromagnetic remote-controlled switch having main contacts 23, 22 in series with auxiliary contacts 21, 20, the auxiliary contacts 21, 20 are the first to open and by so doing remove a short circuit from a blow-out coil 25a which magnetizes pole-plates 10 which attract an armature 31 thereby preventing contacts 23, 22 from opening till the current is at or near the zero of the A.C. cycle. In the form shown the voltage coil 3 normally attracts an armature 4 pivoted at 7. On de-energization of the coil 3, a spring 8 moves the armature 4 about its pivot and the end 4a pushes the contact spring 20 away from the fixed contact 21. A dead-centre spring 5 is also moved so as to press the contact spring 23 to the left but movement of the contact 23 is prevented as already stated till the current is near zero. The contacts 20, 23 are mounted on springs bent as shown, the electrodynamic forces tending to hold the contacts together. In a modification, Figs. 1-3 (not shown), the armature 4 acts only on the contact 23 and the two contact portions 22, 21 have connected between them an additional coil which on overload, by magnetization of the pole plates 10, attracts an additional armature, which is also pivoted at 7 and in its movement opens the contacts 20, 21 and also, through the medium of a link and dead-centre spring, opens contacts in series with the coil 3. The armature 4 is thus released and opens the contacts 23, 22 as before at the zero of the cycle. A bimetal release may also be provided, adapted to break in a similar way the circuit to the coil 3. The invention is shown applied to a three-phase switch the voltage coil 3 being connected between two of the phases.