GB420724A - Improvements in or relating to vacuum or low-pressure gas or vapour apparatus for electric discharges - Google Patents

Abstract

420,724. Converting. ELIN AKT.- GES. FUR ELEKTRISCHE INDUSTRIE, 1, Volksgartenstrasse, Vienna. Nov. 27, 1933, Nos. 33218 and 33219. Convention dates, Nov. 26, 1932 and April 8, 1933. [Class 38 (ii)] Auxiliary electrodes are arranged adjacent the anodes and are fed with a variable intermittent voltage which consists of only the steeply inclined parts of an alternating voltage superimposed on a negative voltage. In one form the grid has applied to it a high amplitude alternating voltage and a negative bias, and a spark gap short-circuits the alternating voltage before it has risen to the top of the curve, giving a grid voltage curve 1, Fig. 2. In a modification, an additional negatively biassed grid is inserted between the first grid and the anode, at the edge of the anodic dark space. In the arrangement shown in Fig. 5, a spark gap Pf breaks down when the grid voltage has risen to a predetermined value and a series resistance R limits the current flow through it. In a modification the inductive resistance of the transformer winding T may be increased and the resistance R omitted. Two valves in parallel, having equal or different breakdown voltages may be used instead of a spark-gap. The grid voltage may be phasedisplaced by a rotating controller or, as shown in Fig. 8 wherein a five-core transformer for a six-phase system is shown, by passing a continuous current through windings on the first and fifth cores and regulating the magnetization currents by a control switch SR. A condenser system C, so arranged that without presaturation it delivers a leading current through the resistances W and with maximum saturation a lagging current may be added. The steepness of the control voltage curve may be increased by using a higher harmonic, for example the third. In switching off, either in normal operation or on short circuit or backarcing, the permanent negative voltage is allowed to remain, and hand or automatic operation switches off the alternating voltage source, preferably on the primary side.