GB691169A - Improvements relating to air-blast switches - Google Patents

Abstract

691,169. Air-blast switches. CZECHOSLOVAK HEAVY ENGINEERING WORKS, NATIONAL CORPORATION, and GROSSE, V. May 14, 1948 [May 15, 1947], No. 13421/52. Divided out of 13343/48. Class 38 (v) An air-blast switch has main current-interrupting contacts 1, 2 in parallel with a resistor 5 in series with an auxiliary spark-gap-type interrupter 3, 4 at which arc extinction is delayed with respect to the opening of the contacts 1, 2, and additional current-carrying contacts 33, 34 in parallel with the main interrupting contacts 1, 2, the contacts 33, 34 being disposed nearest to, and the spark gap 3, 4 farthest from, the supporting insulator 11 of the switch so as to minimise the stresses acting on the insulator due to electrodynamic forces. When the switch is opened, the contacts 33, 34 are initially opened by the air blast, the contacts 1, 2 being held closed by pneumatic means (not shown) until the contacts 33, 34 are open. The air-blast acting on the contact 1 then opens the contacts 1, 2, a slide-valve (not shown) associated with the contact 1 admitting compressed air through pipes 16, 17 to the extinguishing chamber 8 of the auxiliary interrupter when the contacts 1, 2 are open. The arc drawn between the electrodes 3, 4 is extinguished by the blast through an insulating nozzle 25, this blast exhausting into the main exhaust chamber 31 of the switch through a pipe 30 formed as an ejector to avoid the return flow into the auxiliary interrupter of blast gases flowing through the nozzle contact 2 of the main interrupter. Air flowing from the chamber 8 through a pipe 21 into a cylinder 22 opens an isolator 6, 6b. If automatic reclosing of the circuit controlled by the switch is required when the air blast is shut off, the isolator 6, 6b is maintained closed throughout the operation of the switch by the application of compressed air through a pipe 41 to the closing cylinder of the isolator.