GB534828A - Improvements in or relating to a.c. electric circuit-breakers having arc-control devices - Google Patents

Abstract

534,828. Fluid-blast switches. REYROLLE & CO., Ltd., A., ALLEN, A., and WILD, R. W. Sept. 13, 1939, No. 25756. [Class 38 (v)] An arc-control device in an alternating-current switch comprises two relatively-rotatable, insulating, cantact-carrying members so disposed one within the other that the arc is drawn in a narrow arcuate space between them, means being also provided for causing a deionizing blast to flow out of the space through one or more vents in the wall thereof. The device of Fig. 2 comprises a movable contact A carried on the rim of an insulating disc A<1> which fills the space between two insulating plates B<2> which, with a cylindrical wall B of short axial length, constitutes the outer member, the whole being secured along with insulating cover plates B' by means of bolts. The plates B<2> extend inwardly towards a metal boss A' which is connected to the contact A and is mounted on an operating shaft A'. The arcing- space C is an enclosure between the rim of A' and member B and is made of tapering section by means of an insulating ring A<5> on the rotor, which ring is of a thickness that increases from the contact A until at about 20 degrees it becomes of constant thickness, so providing a short, relatively wide space for dealing with largecurrent arcs, while providing a long, narrow space for drawing out small-current arcs. Vents B' extend around three-quarters of the periphery of member B from the metal plunger contacts D on the outer structure. The device may be immersed in an oil tank or, as shown, may have linings B<4>, A<6> of boron, fibre or other solid material giving off an extinguishing gas under arc-action. An isolating break may be obtained by moving a coupling-member along the shaft A<4> away from the metal boss A<3> which is suitably insulated therefrom, but, as shown, the outer structure is moved to open a knife-blade coupling D<1>, D<2>. In Fig. 4 a pair of seriesconnected breaks are provided by contacts A on the rotor engaging contacts D on the outer structure B, each break having an arcuate space and vents B<1>. The rotor-travel is about 90 degrees and an isolating break,may be got by rotating the outer structure to disengage contacts D<3> thereon from contacts E' carried by the oil-tank E. The device can be adapted for gas-breaks by providing linings as in Fig. 2. Both the above arrangements can be adapted for polyphase circuits by insulating the connectors A<2> from the common shaft A<4> and superimposing the phases. Fig 3 shows device having vents in the inner structure as in Specification 535,217, which comprises a rotatable insulating tube L with a gas-evolving lining L<1>, in which is embedded a strip contact M co-operating with a fixed contact J in the outer insulating tube H having a gas-evolving lining H<2>. The tube L has a guide flange L<2> and upper and lower bearings K<1>. K<2>. The Specification refers also to delivery of pressure-gas from an external source.