GB433967A - Compounding of electric metal vapour rectifiers by grid control apparatus - Google Patents

Abstract

433,967. Rectifying alternating current. ENGLISH ELECTRIC CO., Ltd., . 28, Kingsway, London, EVANS, W. R., Parkfield, Cannock Road, and RICHARDSON, J. A. ST. C., The Old Rectory, Fradswell, both in Stafford. March 7, 1934, No. 7317. [Class 38 (ii)] A compound characteristic is imparted to a grid-controlled arc rectifier 5 by feeding the grids with the resultant of a dephased A.C. voltage derived from a transformer 6, a steady negative voltage derived from a potentiometer 9 fed by a transformer 7 through auxiliary rectifiers 8, and a variable positive voltage derived from a potentiometer 13 fed by a transformer 10 through auxiliary rectifiers 12 and a variable impedance 11. The latter comprises chokes 11a the cores of which are variably saturated by windings 11c fed by current proportional to the load on the rectifier 5, the arrangement being such that an increase in load current reduces the impedance of the chokes, increases the positive voltage provided by the potentiometer 13, thus decreasing the resultant negative bias on the grids and thereby advancing the ignition to raise the output voltage. Where the D.C. busbars 16 are fed by two rectifiers in parallel, load sharing is effected by providing an equalizer connection 18 between the cathodes. Overload and back ignition protection may be provided by arranging relays on either the A.C. or D.C. side to disconnect the primary of the transformer 6, and if desired the transformer 10, so that the grids receive only negative voltage from the potentiometer 9.