GB407619A - Improvements in or relating to the control of vapour arc rectifiers - Google Patents

Abstract

407,619. Rectifying alternating current; transformers. ENGLISH ELECTRIC CO., Ltd., 28, Kingsway, London, CALVERLEY, J. E., 58, Crescent Road, Rowley Park, and EVANS, W. R., Parkfield, Cannock Road, both in Stafford. Sept. 8, 1933, No. 24950. [Class 38 (ii).] In a grid regulated vapour arc rectifier, the instant at which a positive potential is applied to the grids to render the corresponding anodes conductive is determined by adjusting the relative magnitudes of two A.C. voltages differing in phase the resultant of these two voltages whose phase position in relation to the anode voltage is thus determined being applied through glow discharge tubes to the grids. In the case of a 6-phase rectifier a, three grid transformers respectively excited by primaries 7, 8, 9 associated with the supply network b are employed. Secondaries 10 .. 15 arranged in pairs on the same limbs as the primaries provide voltage components of fixed amplitudes, and secondaries 16 .. 21 arranged in pairs on outer core limbs are adapted to provide voltage components of variable amplitude in dependence upon the current flowing in D.C.-excited coils 4, 5, 6 arranged on the third limbs and adapted to divert a variable proportion of the flux due to the primaries through the limbs carrying the secondaries 16 ... 21. Each grid circuit includes one of the secondaries of fixed voltage, e.g. 12, and one of the secondaries of variable voltage, e.g. 16, the two voltages being 60‹ phase displaced. Each grid circuit also includes a glow discharge tube 22 and an adjustable proportion of a potentiometer 25 associated with a battery 28. The potentiometer tappings are adjusted to take account of inequalities in the characteristics of the tubes 22 so that each tube breaks down at the same value of the resultant A.C. voltage due to the components derived from the two secondary windings. The instant at which this value is attained is varied by varying the current in the coils 4, 5, 6 either manually, or automatically by connecting the coils across a shunt 29 in the rectifier load circuit. The coils 4, 5, 6 are connected in series so that A.C. voltages induced therein by flux due to the primaries 7, 8, 9 balance out. Alternatively, the three cores may be arranged with their third limbs embraced by a single coil 4 as shown in Fig. 4. Where two or more rectifiers operate in parallel, the load is connected to the terminals + L, - L, and the terminal - T1 on the rectifier side of the shunt 29 is connected to corresponding terminals - T2, - T3 etc. of the parallel operating rectifiers as shown in Fig. 5.