GB781378A - Improvements relating to electrical spark gap discharge apparatus - Google Patents

Abstract

781,378. Spark gaps. METROPOLITANVICKERS ELECTRICAL CO., Ltd. July 6, 1955 [July 16, 1954], No. 20823/54. Class 39(1). The centre electrode of a double spark gap is formed in two parts B1 and B2 connected together through a condenser C1 and resistor R3 and each part has an associated triggering electrode P 1 or P 2 . The parts B 1 and B 2 are connected to the mid-point of a potential divider R 1 R 2 which is connected between the outer electrodes A and C. A positive pulse generated at the mid-point of the potential divider by a pulse transformer T is applied between the coupling condenser C1 and the electrode P 2 causing breakdown of P 2 B 2 and then, as condenser C 1 charges up, P 1 B 1 . If C is positive with respect to A gap AB 1 breaks down followed by gap CB 2 . If C is negative with respect to A gap CB2 breaks down followed by gap AB 1 . The arrangement may be connected as a triggering device in the first stage of an impulse generator and ensures that when the generator polarity is reversed there is always an outer electrode which is negative with respect to the centre electrode and facing a triggering- electrode which is positive with respect to its associated electrode, which are the optimum conditions when triggering a spark gap. The spark-gap is designed to operate in still air at atmospheric pressure but may be enclosed in an envelope filled with gas at a pressure greater than atmospheric. Spark quenching means such as an air blast may also be provided. The centre electrode, Fig. 2, comprises two hemispheres 1, 2 for example of copper fitted with molybdenum inserts 3, 4 having central holes 5, 6 through which project molybdenum triggering rods 7, 8 held in brass bushings 9, 10 attached by screws, which are preferably staggered to prevent electrical breakdown, to an insulating disc 11 for example of ebonite to which the hemispheres 1, 2 are also attached. The triggering rods 7, 8 are surrounded by glass tubes 12, 13 which are ground at one end and fastened at the other end by wax to the brass bushings 9, 10. A resistor 14 and condenser 15 are connected inside the electrode so that only the two connections to the pulse transformer are brought out via channels in the disc 11. Specification 578,510 [Group XL] is referred to.