GB375309A - Improvements relating to electric switches and circuit breakers - Google Patents

Abstract

375,309. High tension switches. BRITISH ELECTRICAL & ALLIED INDUSTRIES RESEARCH ASSOCIATION, WEDMORE, E. B., and WHITNEY, W. B., 36, Kingsway, London. March 18, 1931, No. 8332. [Class 38 (v).] Sparking, preventing.-In a fluid-blast switch as described in Specification 278,764, [Class 38 (v), Electric switches &c.], the arc root is prevented from biting into the tip of the electrode by passing the main current through a spiral or helical coil which acts on the arc and causes it to rotate around the electrodes and constantly move its arc roots. By choice of field concentrations the arc may be caused also to move somewhat against or with the fluid blast. In the construction shown in Fig. 1, the orifice contact b bolted to the upper part of the pressure chamber e has its upper part d made of soft iron and is surrounded by a helical conductor connected at its upper end to the part d and at the other end to the lead-in conductor g. The lower end of the helix is held down by the bracket against upward movement due to electrodynamic action between the coils, and the movable plug-like contact c is provided with a soft iron ring q to improve the alignment of the field due to the helix in the axial direction of the helix. When, at break, an arc is drawn across the shortest path between the separating contacts the field is substantially at right-angles to it and causes it to rotate electrodynamically like the spoke of a wheel. In a modification, Fig. 2, the fixed copper electrode k has an outer part with saw-cuts r filled with insulation so as to constitute a helical coil connected to the lead-in terminal g at the upper end and integral with the remainder of the electrode at the lower end. The soft iron portion d is of cupped form fitting upon inturned portions of the electrode k and the plug contact is provided with an iron core. In another form, the orifice contact has over it a converging copper strip helix terminating at the reduced end in a connection with a supporting spider connected with the lead-in. The inner movable contact may be furnished with the coil to produce the field. The invention may be used in conjunction with the arrangement described in Specification 375,308 for holding the arc in the region of maximum blast.