GB1437108A - Vacuum electric circuit interrupter - Google Patents

Abstract

1437108 Arc control in vacuum switches GENERAL ELECTRIC CO 16 Nov 1973 [19 Jan 1973] 53393/73 Heading H1N A high current vacuum interruptor of the kind comprising hermetically sealed envelope 11 evacuated to a pressure not exceeding 10<SP>-4</SP> torr and containing two interleaved sets of parallel rod electrodes 16, 18 forming a ring the alternate members of which are of opposite polarity, is provided with a tubular metal shield 23, at least a major portion of which surrounds the electrode ring and is electrically isolated from it, this shield further comprising metal partitions 40 projecting radially into the spaces between adjacent electrodes 16 and 18 to divide each space into two series-related arcing gaps which share the recovery voltage between adjacent electrodes. In the preferred embodiment the electrodes 16 and 18 are connected at their outer ends to the metal top and base plates 15 and 17 of the envelope 11, the insulating side-wall of which is divided into two portions 13 and 14. A flange 20 sealed between the wall portions supports the tubular shield 23 and also auxiliary shields 71, 72. The current carrying contacts comprise a fixed contact 30 rigidly connected to the top plate 15 and a movable contact 32 sealed through the bottom plate 17 via a bellows 38 located in a housing extension 39. The stroke of this contact is preferably such as to provide a gap of greater length than that of the sum of the arcing gaps between adjacent electrodes 16 and 18, and in the embodiment is approximately 2 inches. Further auxiliary shields 70 and 73 are fitted. The tubular shield 23 comprises a cylindrical body portion 19 with metal end caps 50 and 52. The shape and location of this shield is such as to obtain substantially equal capacitance between the shield and each of the electrode assemblies when the interrupter is open. The gap between contacts 30, 32 and partitions 40 is at least equal to that between electrodes and partitions. In an alternative embodiment (Fig. 3, not shown) the shield partitions are curved concentrically around the adjacent electrodes and welded at their outer edges, so that the partitions themselves form the body portion of the shield. This arrangement provides a more uniform field around the electrodes. USA Specification 3,679,474 is referred to.