GB386095A - Improvements in high potential electric switches - Google Patents

Abstract

386,095. Sparking preventing in switches. SIEMENS-SCHUCKERTWERKE AKT.-GES., Siemensstadt, Berlin. Dec. 3, 1931, No. 33559. Convention date, March 11. [Class 38 (v).] A current switch S, designed to interrupt currents at low voltage only, but capable of carrying large currents during normal working, is connected in parallel with a power switch L designed to interrupt large currents at high voltage, and the power switch circuit is provided with a choke D, the reactance of which regulates the distribution of current between the switches during normal working, but is greatly reduced on the occurrence or cutting out of a shortcircuit by corresponding proportioning or controlling of its inductive flux. The switch S is closed after the switch L, but opened before it. The choke D is arranged to be saturated by a current well below the short-circuit current value, so that when short-circuit current flows the current to be interrupted by the switch S, and the potential across it in the open position, are greatly reduced. If the resistances of the two switch loops are normally such as to give a proper current distribution, it is necessary to provide a choke for the current switch loop, which is not saturated on the occurrence of a short-circuit. In a modification both switch loops have chokes with secondary windings connected in opposition. When a shortcircuit is interrupted, the opening of the switch S reduces the reactance of the power switch loop.