GB1174766A - Improvements in Spark Gap Devices - Google Patents

Abstract

1,174,766. Surge diverters. E.M.P. ELECTRIC Ltd. 3 April, 1967 [7 Jan., 1966], No. 811/66. Heading H2H. A spark gap device for a surge diverter generally similar to that described in Specification 908, 240 is modified to cause the arc to contact a surface of the extinction chamber before reaching the periphery thereof. This is achieved by producing asymmetry between the chamber and the plane in which the arc moves outwardly from the electrodes under the action of the magnetic field. In one embodiment, Fig. 1 (not shown), the chamber has a trapezoidal section and the electrodes are disposed so that the plane of arc movement is mid-way between and parallel to the two parallel sides, thus causing the arc to be cooled as it runs along the other two sides of the chamber. In another embodiment, Fig. 2 (not shown), the chamber is elliptical in section and the plane of arc movement is displaced from the major axis by suitable disposition of the electrodes. The magnet blow-out effect is provided by permanent magnets in the first embodiment and by electromagnet coils in the second embodiment, the magnets and coils being mounted on each side of the chamber. The embodiment shown in Fig. 3 uses a symmetrical arrangement of chamber section and electrodes, but displaces the plane of arc movement CC by appropriate shaping of the permanent magnets 10 to produce an asymmetrical magnetic field relative to the chamber. Such asymmetry may be produced by shaped polepieces or suitably disposed electros magnet coils. The embodiment of Fig. 5 usediscs 17, 18 each of whose four quadrants are provided with shaped surfaces alternating from a flat profile 15 to a depression 16, the discs being opposed so that profiles 15 and depressions 16 are matched for each quadrant to produce the asymmetrically-shaped chamber shown. Centre portions 19 provide the space for the electrodes (not shown). Shaping and overlapping of the profiles, depressions and other portions of the discs enable channels, steps and grooves to be provided in the chamber if desired, Fig. 4 (not shown). The permanent magnets 10 are shaped to completely enclose the arc extinction chamber.