GB392445A - Improvements in electric switches provided with arc quenching means operating upon the expansion principle - Google Patents

Abstract

392,445. Liquid-break switches. SIEMENS-SCHUCKERTWERKE AKT.- GES., Siemensstadt, Berlin. Oct. 29, 1932, No. 30426. Convention date, Feb. 25. [Class 38 (v).] A switch in which the arc is extinguished by means operating on the expansion principle, according to which the liquid wherein the arc is struck is confined by a wall surrounding the break gap, and the vapour generated under pressure by the arc is caused to be discharged through expansion apertures opening out into discharge spaces free of liquid, has parts of the surface of the wall directed towards the arc and'located out of the vapour-path through the apertures, but in the vicinity of the arc, and of such character that they retain liquid despite the violent expansion of the vapour which occurs on the said discharge. In this way the retained liquid is vaporized and the vaporization persists through the zero of the A.C. cycle. The retaining means may comprise grooves, or undulations in the wall surface, or the latter may be roughened or formed with small holes, and the liquid may normally fill the arc chamber or be introduced periodically, as during each opening process. As liquids there may be used water or aqueous solutions of, for example, glycols, incombustible inorganic or organic insulating liquids, as triaryl phosphate and carbon tetrachloride. The arc chamber comprises a series of insulating rings, as 30, provided with grooves 52 and threaded on bolts 54 so as to be normally held against one another by springs 43 which are located between a member 39 and a plunger 38 slidable therein. The movable contact 47 in the closed position passes through a fixed contact 41 and depresses a piston 42 having valves 44 which, with a valve 45; permit liquid to flow from the reservoir into the switch chamber 40 when the piston is moved downwards. When the switch is being opened, the piston 42 follows the contact 47 and fills the spaces in the centre of rings 30 with the liquid. When 47 leaves 41 the arc formed vaporizes the liquid until the vapourpressure is enough to separate the. rings, whereupon a sudden discharge of vapour occurs and produces a lowering of the pressure within the chamber. This pressure-drop causes evaptration of the liquid retained in the grooves 52, so that large amounts of relatively cool vapour penetrate the arc, and are discharged, without however disturbing the retained liquid in the grooves. The Specification refers also to a form in which the arc chamber may be open to the atmosphere and the discharge occurs into a partial or complete vacuum, and shows a form in which vertical corrugations are employed.