GB671906A - Improvements in and relating to electric valve converting circuits - Google Patents

Abstract

671,906. Rectifying. BRITISH THOMSONHOUSTON CO., Ltd. Sept. 7, 1950 [Sept. 9, 1949], No. 22077/50. Class 38 (ii). In a converting system in which electric discharge apparatus is fed from a polyphase supply, to provide time for the apparatus to partially deionize and reduce the probability of arc-back, the current curve at commutation is flattened by reactors each having a linear part connected in series with a primary winding of the main transformer, and a self-saturating part so connected that it carries part of the current of another primary winding of that transformer. In Fig. 1 the main primary windings 5, 6, 7 of a transformer which supply a D.C. line 1, 2 through rectifying ignitions such as 15, each in series with linear parts 27 of inductors, are connected in delta to a threephase supply 3, and self-saturating parts 28 of the inductors are connected in the line connections to the delta. The line current leads the phase current by 30 degrees so that parts 28 desaturate and flatten the current curve a short time before it reaches zero and a low value of anode current is maintained just before the application of reverse voltage across each ignitor. In a modification, the transformer primary windings in series with the linear part of the inductors are connected in Y and the self-saturating parts are connected in delta, Fig. 2 (not shown).