Patent GB-400294-A (GB)
Title: Improvements in and relating to electric regulating systems
IPC: G05F1/16
Filed: 1932-04-27
Abstract: 400,294. Automatic regulation. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Bedford, B. D. ; 329, Germania Avenue, Schenectady, New York, U.S.A.) April 27, 1932, No. 12116. Convention date, April 27, 1931. [Class 38 (iv).] In a voltage regulating system for alternating current circuits, in which a load circuit 10 is connected to a supply circuital 11 through an inductive winding and a plurality of electric valves, means are provided for transferring the load current between the valves at any desired point in the cycle of alternating potential for the purpose of regulating the average voltage of the load circuit. In one arrangement, Fig. 1, the inductive winding is an autotransformer 12 having bucking and boosting terminals 14, 15 which are respectively connected to the load circuit 10 through pairs of electric valves 1, 3 and 2, 4 reversely connected in parallel. The valves are preferably of the vapour electric discharge type and are provided with grids excited from the secondary windings 21 .. 24 of a grid transformer 17, the primary winding of which is energized from the supply circuit 11 through an arrangement, such as a condenser 19 and resistance 18, for advancing the phase by a small angle. The grid circuits of the valves 1, 3 include resistances 26, 29 connected to the secondary windings 27, 30 of a transformer 25 through unilaterally conductive devices 28, 31, by which means the positive half cycles of a potential variable in phase' are introduced into the grid circuits. The phase shifting arrangement 20 comprises an inductive winding 32 connected across the load circuit 10, a reactance 33, and the primary winding 34 of a transformer 35, the primary winding of the transformer 25 being connected, as shown, between the mid-point of winding 32 and the junction between 33 and 34. The secondary of transformer 35 is short-circuited through a pair of valves 36, 37 to give the winding 34 a resistance characteristic. The valves 36, 37 are controlled, in response to the voltage of the load circuit 10, through an arrangement comprising a rectifier bridge 38, a resistance bridge 39, the arms of which are made of resistances having dissimilar characteristics, and current smoothing means, such as an inductance 40 and condenser 41. The potential supplied by the phase shifting arrangement 20 varies in phase in response to variations in the voltage of the load circuit 10, and determines the period in each half cycle at which the load is transferred from the tap 14 to the tap 15. The manner in which the arrangement operates with lagging, leading or unity power factor loads is described in the Specification with the aid of diagrams. In a modification, Fig. 5, the autotransformer is replaced by a transformer 45 provided with bucking and boosting primary windings 46, 47 and a secondary winding interconnecting the supply and load circuits, the valves 1, 3 being associated with the boosting winding and the valves 2, 4 with the bucking winding. The grids of the valves 2, 4 are excited from a grid transformer 48 through a phase advancing arrangement comprising a resistance 18 and condenser 19, while the grids of the valves 1, 3 are excited from the secondary windings of a transformer 49 energized from the secondary 50 of a phase-shifting transformer connected to a polyphase circuit 52, which is synchronized with the load circuit 10 or energized directly therefrom through a phase-splitting device. The secondary member 50 is adjusted in response to the voltage of the circuit 10 by means of a motor 53 connected to the polyphase circuit through a reversing switch 56, the position of which is controlled by a voltage coil 55. In a further modification, Fig. 6, the number of cathode potentials is reduced to two by providing the transformer 45 with two primary windings, each having a bucking and a boosting portion. By providing an additional autotransformer 57, as shown in Fig. 7, all the cathodes may be operated at the same potential. In other arrangements, this result is secured by connecting additional transformers in series with the boosting and bucking windings of the transformer 45. In a further arrangement, four additional valves, receiving the same grid excitations as the valves 1 .. 4, are provided. Specification 399.240 is referred to.