GB639394A - Improvements in and relating to electrical switching devices having arc preventing arrangements - Google Patents

Abstract

639,394. Sparking preventing in switches. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. June 26, 1946, No. 19069. Convention date, April 25, 1942. [Class 38 (v)] A high-power D.C. switch 9, 10, controlling a load 3 is shunted by a mercury-cathode discharge tube 4 which strikes when the switch opens, thereby absorbing the arc. An auxiliary switch 11 operated as the switch 9, 10, opens, controls a relay 13 which after a short interval insufficient to damage the switch 9, 10, closes contacts 14, enabling a condenser 15 to discharge through an ignition electrode 6, thereby initiating discharge of the tube 4. After a further short interval when the gap of the switch 9, 10, is sufficiently long and deionized, by known means, to prevent restriking of the arc, contacts 16 close, enabling a condenser 18 to ignite a tube 17 through which a condenser 8, charged by a device 19, discharges, thereby extinguishing the tube 4. The tube 17 is extinguished when the condenser 8 and an auxiliary condenser 20 become charged, the capacity of the latter being such that the greater proportion of the circuit voltage 1 appears across its terminals. For periodic operation of the switch a leakage resistance 21 is provided to enable the condenser 20 to discharge in the interval. The dimensions of the tube 4 and its time of operation must be such that after it has operated, the voltage required to restrike it is greater than the circuit voltage; a small tube of about 100 c.c. capacity is used, the theory being explained in the Specification with the aid of a graph, Fig. 3 (not shown). A switch may replace the tube 17, Fig. 1 (not shown), and the arrangement is also suitable for A.C. interruption during the half-cycle which is conducted by the tube.