GB447239A - Improvements in and relating to circuit arrangements for the control of the discharge in gas or vapour filled discharge vessels - Google Patents

Abstract

447,239. Converting. SIEMENSSCHUCKERTWERKE AKT.-GES., Siemensstadt, Berlin. Oct. 14, 1935, No. 28350. Convention date, Jan. 23. [Class 38 (ii)] [See also Group XL] In arrangements for rectifying A.C. or for converting D.C. to A.C. and for similar purposes in which current is transmitted through gas or vapour discharge apparatus wherein the anodecathode path is normally blocked by a negatively charged grid or sleeve, ignition is effected at a predetermined moment by lowering the potential of the anode to approximately the potential of the cathode. In the rectifying arrangement shown, a discharge device 1 having a mercury cathode on which an excitation arc is continuously maintained by an auxiliary anode 5 has its grid 3 negatively biassed by a D.C. source 6. The A.C. supply 11 and load 12 are connected in series across the anodecathode path of the discharge device, and starting of the discharge at each positive half cycle of anode voltage is effected by switching across the anode-cathode path a condenser 8 so that the anode potential falls substantially to that of the cathode and rises again as the condenser becomes charged. A resistance 10 is connected across the condenser for effecting its discharge between successive periods. The self capacity of the resistance may be made such as to render the condenser unnecessary. Regulation is effected by varying the timing of the switch G. In an alternative arrangement, ignition is effected by arranging a transformer to inject into the anode circuit potential peaks adapted momentarily to neutralize the positive voltage applied to the anode. As a further modification, the grid may be brought to the required potential by connecting it to the cathode through a resistance, in which case the connection may be effected within the discharge vessel.