GB1319709A - Voltagesurge arresters - Google Patents

Abstract

1319709 Cold-cathode tubes SIEMENS AG 19 April 1971 [16 March 1970] 24047/71 Heading H1D In a voltage-surge arrester, a cup-shaped cylindrical electrode 1 forms part of a vacuumtight envelope containing a solid cylindrical electrode 2 extending into said cup-shaped electrode and supported coaxially therewith by an end-cap 4 which forms part of said envelope, an annular body 3 of insulating material being positioned around said solid electrode and spaced therefrom to complete said envelope via respective metal wall sections 5, 6 sealing said annular body 3 to said end-cap 4 and said cupshaped electrode 1, the outer diameter D ka of said cup-shaped electrode 1 being not more than 15 mm., its internal diameter D ki being not more than 2 mm. greater than the diameter D z of said solid electrode 2, and the material or materials of said electrodes and their respective dimensions being such that in the event of excessive overload a short-circuit is produced due to melting of said solid electrode 2 before said envelope is ruptured by the heating of said electrodes. Formulµ are given for calculating the diameters of the electrodes to ensure that melting does not occur for normal overload by current pulses of high magnitude and short duration, e.g. 100 kA for 100 Ás. The electrodes are preferably of the same material, e.g. Fe, and the diameter D z is not less than 3 mm. The metal reactions 5, 6 should have a thinner section than the end-cap 4 and electrode 1. The envelope is filled with an inert gas.