Patent GB-517622-A (GB)
Title: Improvements in or relating to electric circuit-breakers having arc-control devices
IPC: H01H33/24
Filed: 1938-08-02
Abstract: 517,622. Fluid - blast switches; switchgear structures. REYROLLE & CO., Ltd., A., and HARLE, J. A. Aug. 2, 1938, No. 22810. [Class 38 (v)] An A.C. fluid-blast circuit-breaker has a laterally vented, insulating arcing enclosure so arranged that a substantially-uniform electrostatic field is produced throughout the enclosure when no current is flowing, partly or wholly by appropriately - shaped and dimensioned end shields disposed at the two ends of the device and respectively connected, at least during the initial opening movement, to the arcing contacts, whereby the dielectric conditions are so controlled that the possibility of re-ignition of the arc after the current zero is reduced, which object may be aided by prolonging the blast after the current-zero. The invention may be combined with that of Specification 517,623, in which the vents have aligned throats and discharge in different directions, and Figs. 5-14 (not shown) appear also in that Specification. The invention is also applicable to the constructions described in Specifications 516,529, 516,530, 516,531, and 516,532. The enclosure of Fig. 1, is a central space A<2> in an insulating structure A, the vents A<1> extending from the space A<2>, on the opposite side of an enlarged part thereof, to the outside. The fixed-contact structure B has an extended finger B<1> on the side adjacent the aligned ventthroats, so that the arc formed between it and the movable rod-contact C is drawn out close to the throats, the contact C preferably acting as a valve successively to uncover the throats. The contacts B, C are housed in metal shields B', C<2> which approximate to portions of largediameter spheres and are attached to metal endplates B', C' secured together by suitablyinsulated bolts B<4>. The external contour of A conforms to the electrostatic lines of force, and the vents A<1>, which lie in the same axial plane, conform to the shape of equipotential surfaces between the shields, so ensuring a uniform potential gradient along the enclosure. The contact C is moved beyond the shield C<2> in the open position, and carries a piston C' working in a cylinder C' formed in the shield, the blast-gas admitted at C', C' serving also to operate the contact. The shields B', C<2> of Fig. 3, have flat surfaces and the structure A has a more or less cylindrical surface conforming to the lines of force. The vents A' lie along equipotential surfaces parallel to the shield surfaces, but are angularly spaced so as to discharge in different directions. The gas-blast supply pipe C' is independent of the pipe C<5> and opens into inlet ports A' opposite the vents A'. In addition to the conducting shields, spaced annular metal discs may be embedded in the structure A, the top and bottom ones being connected directly to endplates by metal bolts so as to have the same potential as the end-plates. The sizes of the discs may be graded so as to produce the appropriate voltage distribution, or that effect may be produced by means of a remotely-disposed voltage divider, the ends of which are connected to the end plates and intermediate taps connected to the inserts.