Patent GB-382612-A (GB)
Title: Improvements in and relating to transforming electric currents
IPC: H02M3/31
Filed: 1931-07-16
Abstract: 382,612. Converting electric currents. INTERNATIONAL GENERAL ELECTRIC CO., Inc., 120, Broadway, New York, U.S.A. -(Assignees of Allgemeine Elektricitõts, Ges. ; 2, Friedrich Karl-Ufer, Berlin.) July 16, 1931, No. 20423. Convention date, July 16, 1930. [Class 38 (ii).] In an arrangement for transforming direct current voltage through an alternating voltage into another direct current voltage by means of grid-controlled discharge vessels, the voltage changing transformer has a rhythmically intermittent separate excitation. which is dependent on the load, and effected by A.C. voltage of a nearly rectangular wave shape, and the anode circuits of the discharge vessels include interdependent impulse transformers. In Fig. 1 a thyraton or grid-controlled discharge vessel 1 with anodes 4, 5 and grids 2, 3 is connected through terminals 8, 9 to the primary 22 of the transformer 26, the secondary 23 of which is connected through 18, 19 to the rectifier 11. Included in the transformer is a tertiary winding 26, excited by a generator the current through the field windings of which is caused to be dependent on the load. Included in the anode circuits are windings of impulse transformers 30 of the form shown in Fig. 2 wherein the limb winding 31 is connected across terminals 8 in the thyraton anode, circuit, and the winding 32 across terminals 19 in the rectifier circuit; and both wound to give a field in the same direction, whilst a third yoke winding 35 carries a fixed current in the opposite direction. to just neutralize this field, and, in addition, receives current impulses from a separate generator. A similar transformer is used across terminals 9, 18. When the grid 2 is positive, an arc is struck at the anode 4 of the thyraton valve and a corresponding voltage, generated in the upper half 24 of the winding 21 of the transformer, produces a residual voltage for maintaining the arc and covering losses. When the voltage impulse is produced in the impulse transformer, the arc is extinguished at both the thyraton and the rectifier anodes 4, 14 respectively and, the voltage of grid 2 having meanwhile become negative, the arc remains extinguished until a fresh voltage impulse in the anode circuit and a positive grid reproduces it ; with a similar but displaced cycle taking place at the anode 5, the arc is swiftly transferred from one anode to another. The practical details of an arrangement with four discharge paths are illustrated in Fig. 4 in which a row of generators and commutators is mounted on a common shaft driven at a uniform speed by a motor 80. The windings 21a, 21b are excited from a generator 72, the field of which is excited by a source of voltage proportional to the voltage of the system' 10 and by a field winding 74 fed by a generator 71 having an excitation 75 dependent on the load. A quick-acting-regulator 76 is operated by resistances 91, 92 in the primary and secondary direct current lines respectively so that this excitation is adjusted in conformity with load variations. Generators 77 regulated by watt meters 78 or resistances 79 cover the copper and iron losses of the transformer 26. A separate generator 82 supplies voltage impulses to the impulse transformers, the windings 35 receiving, independently of these impulses, the compensation current supplied by the generator 71. The grids 2, 3 are supplied through a commutator 89 from a source of voltage 90.