GB787846A - Improvements relating to high-vacuum electric circuit-breakers - Google Patents

Abstract

787,846. High-tension switches. E.R.A. PATENTS, Ltd. Nov. 9, 1955 [Aug. 9, 1954], No. 23129/54. Class 38 (5). A high-vacuum A.C. switch has a pair of relatively-movable main current-carrying electrodes C, D and a pair of relatively-movable subsidiary electrodes L, M of a material at which the arcing voltage is greater than that of the material of the main electrodes, the electrodes and an operating mechanism being so arranged that the subsidiary electrodes open last but at the end of their separating movement lie behind the planes of the surfaces of the main electrodes so that the arc is initiated at the subsidiary electrodes and then transferred to the main electrodes. In the arrangement shown, a contact-pressure spring R is interposed between an enlarged part Q of the movable subsidiary electrode M and a stirrup P secured to an operating member K. A strong spring S is interposed between the stirrup P and a member O carrying the movable main electrode D and a weak spring T is interposed between the member 0 and the lower surface of an extension H of the envelope A. When the switch is opened the spring T is first compressed so that the electrode D is withdrawn whilst the electrodes L, M remain in contact. Then as the downward movement of the member K proceeds the spring S is compressed and the electrode M is drawn down into the position shown. Flexible connections X, Y interconnect the moving parts and glass sleeves V, W are provided at areas of sliding engagement to avoid arc-like discharges. The main electrodes may be of copper and the subsidiary electrodes of tungsten. Metal, semiconducting or high-resistance shields may be associated with the main electrodes. In an alternative arrangement the auxiliary electrodes may be sleeves surrounding the main electrodes.