GB683804A - Improvements in and relating to air blast high voltage electric circuit breakers - Google Patents

Abstract

683,804. Air-blast switches, oil-break switches. BRITISH THOMSON-HOUSTON CO., Ltd. March 29, 1949 [April 6, 1948], Class 38 (v) A circuit-breaker has main interrupting contacts 14, 15 of the air-blast type and oil-break insulating contacts 64, 65, a single fluid motor 6 actuating the interrupting contacts directly and the isolating contacts through an overcentre toggle 84, 86, so that the isolating contacts open after nd close before the interrupting contacts. The circuit-breaker is shown in the "closed" position and on manual or other operation of the switch 34, a valve 8 is moved by the solenoid 36 to admit pressure air from the container 7 to the "opening" cylinder 16, and a valve 9 is opened by the solenoid 49 to admit pressure air to the arc-extinguishing chamber 11. The piston 17 is driven upwardly and by means of a rack 28 turns a pinion 29 on its fixed spindle 30 to move a rack 32 interconnecting the moving interrupting contact 15 with the "closing" piston 19. Thus the contact 15 is moved down to open the circuit, the are formed at the contacts 14, 15 being extinguished by the blast through the opened valve 9, pipe 46 and nozzle contact 14. As the pinion 29 turns, it turns the toggle link 86 which is fixed to it, and initially straightens the toggle 84, 86, so that during the initial part of the opening movement of the contact 15, the isolating contact 65 is merely moved to the left against the bias of the resilient mounting of the fixed isolating contact 64. The oil-break isolating contacts 64, 65 are opened as the pinion 29 turns the toggle 84, 86 beyond its straight position. To re-close the circuit breaker, switch 57 is operated to cause valve 8 to admit gas to the cylinder 18 so as to move the piston 19 from the bottom to the top of the cylinder, the isolating contacts 64, 65 being closed first as the links 84, 86 pass through their central position. The insulating bushing 71 carrying the fixed contact 64 is supported by an earthed plate 72 which permits the use of a bushing-type current transformer 74. Specifications 541,321 [and 549,756 are referred to.