GB354890A - Improvements in electric switches with arc extinction by selfgenerated vapour-pressure - Google Patents

Abstract

354,890. High-tension switches. SIEMENS-SCHUCKERTWERKE AKT.-GES., Siemensstadt, Berlin. May 27, 1930, No. 16361. Convention date,' June 18, 1929. [Class 38 (v).] In A.C. switches the arc is extinguished by opening the circuit under a conducting or semiconducting liquid, such as water, in a vapour chamber which is kept closed until most of the liquid has been turned to vapour at a high pressure. The chamber is then suddenly opened to release the pressure, the consequent expansion of the vapour extinguishing the arc at the zero of the cycle. A vapour chamber 20 containing the fixed contact 27 has an upper insulating part and a lower part 21 of metal up to the level of the insulating liquid, which may be water or an electrolyte. When the switch is opened, the arc formed causes the liquid to vaporize, and as the movable contact 29 leaves the opening 30 in the chamber, a sudden expansion of the vapour occurs whereby the vapour condenses about the ions and deionizes the arc path. The vapour is condensed in a chamber 23 insulated from earth by a condenser-type insulator 25 and communicating with the chamber 20 through a non-return valve 33. In another form, Fig. 4 (not shown), a space is provided above the aperture 30 communicating by means of two pipes with an overhead condensing chamber from which the liquid can be returned to the vapour chamber. Two vapour-breaks in series may be arranged in parallel with a main air-break, the whole being pneumatically operated, Fig. 3 (not shown). The Specification as open to inspection under Sect. 91 (3) (a) refers also to the use, as switch liquids, of oil, mercury, and carbonic acid. This subject-matter does not appear in the Specification as accepted.