Patent GB-536451-A (GB)
Title: Improvements in or relating to a.c. electric circuit-breakers
IPC: H02B1/00
Filed: 1939-11-13
Abstract: 536,451. Gas-blast switches; actuation of switches; switchgear structures. REYROLLE & CO., Ltd., A., ALLAN, A., and AMER, D., F. Nov. 13, 1939, No. 29951. [Class. 38 (v)], The arc formed on separating the contacts of a gas-blast switch in an enclosure, extends between arcing-tips A<3>, B<2> close to the throat of a lateral vent F, the blast flowing around one or both tips in addition to through, the gap. The tip B<2> may be on the movable contact, Figs. 5 and 6 (not shown), but in Fig. 1, both tips are on respective fixed contacts A, B adapted to be bridged by a number of spring-pressed contactfingers C<4> on a rod C<1>, which is urged to closed position by a spring C<2> and carries a piston C<3> sliding in the cylindrical contact B, whereby the blast-gas also opens the contacts. The gapdistance d is chosen such that its breakdownvoltage exceeds normal voltage but is less than the surge voltage set up by arc-suppression at a point well away from current-zero. The nozzlethroat is wider than, and spaced from, the arcing tips to allow the blast to flow between and around the latter, Fig. 2, but for extra-high voltage, the middle part of the throat may be relatively narrow as described in Specification 536,452, Fig. 3, 4 (not shown), to concentrate the blast on the arc. Also the gas-flow channels are made smooth by suitable modification of the contacts. Modifications are also described employing spring blade contacts,. the blast-conduit being disposed around the fixed contact. A switch according to Fig. 1, can be arranged in series with an isolator in a horizontally withdrawable switchgear structure, the layout being such that the arc is electrodynamically bowed into the nozzle, Fig 7. Busbar and cable socket-contacts G<1>, G<2> cooperate with plug contacts J,. J<1> connected respectively to the fixed contacts. L<1>, A of the isolator and gas-blast. switch, the movable isolator-contacts L<2> being in sliding engagement with contacts L' which are strap-connected at L<5> with the carrier B' of contact B. The contact L<2> is pivoted to a floating lever M which is pivoted to a crank M' and to a lever M<2> pivoted to a bell-crank lever M' on a spindle M". The other arm M<3> is linked at M<5> to a lever M<6> operated by the piston M' of a pneumatic motor M<8>. When the circuit is opened, a latch N<2> frees the rod C', and compressed air from reservoir P is admitted above a piston P<2> which opens valve P<4> to admit the operating and deionizing fluid to the main switch. Air also is admitted above piston M', but the lever M' is locked by a latch N until the opened rod C<1> engages a plunger N<6> which rotates a shaft N<5> so that a projection on it (not shown) deflects the latch Shaft N' is locked until a projection N' drops into a notch N<4> on rod C<1>. Opening of the isolator operates a control valve (not shown) for cutting off the gas-supply, whereupon the springs C<2> reclose the main switches and reset the latches N. The circuit is again made by admitting gas beneath the piston M' to close the isolator which is again latched at N.