GB364345A - Improvements in electrical switches with arc extinction by means of self-generated vapour - Google Patents

Abstract

364,345. High-tension switches. SIEMENS-SCHUCKERTWERKE AKT.-GES., Siemensstadt, Berlin. Jan. 10, 1931, No. 907. Convention date, Jan. 25,1930. [Class 38 (v).] Relates to switches in which the circuit is broken (between contacts 17, 18) under an electrolyte in a metal switch chamber 11 and the arc at break generates vapour pressure in the switch chamber the sudden expansion of this vapour (when the plug contact leaves the chamber) serving to deionize the arcpath and cause extinction of the arc at the zero of the A.C. cycle. According to the invention, auxiliary contacts in the form of an open cylinder 19 are connected in parallel with the plug contact and extend into an annular chamber filled with electrolyte and surrounding the switch chamber. In this way, when a relatively low current of a value inadequate to set up sufficient arcing to develop the necessary vapour pressure is to be broken, the switch acts as a resistance switch, the resistance in circuit increasing as the main and auxiliary electrodes are withdrawn and the circuit is finally broken, sparklessly, when the main electrode (which is larger than the auxiliary electrode) leaves the electrolyte. With higher values of current an arc is drawn between the electrodes 17, 18 and the arc extinguished by the expansion of the resulting vapours when the electrode 18 leaves the chamber. The production of the necessary vapour pressure is facilitated by the increased current diverted through the arcing contacts as the parallel resistance increases on withdrawal of the electrodes.