Patent GB-399240-A (GB)
Title: Improvements in and relating to voltage regulating systems
IPC: G05F1/16
Filed: 1932-04-16
Abstract: 399,240. Automatic regulation; transformers. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. (Assignees of Boyajian, A. ; 55, Stratford Avenue, Pittsfield, Massachusetts, U.S.A.) April 16, 1932, No. 10955. Convention date, April 17, 1931. [Classes 38 (ii) and 38 (iv).] In a voltage regulating system, a load circuit 11 is connected to a.supply circuit 10 through a transformer winding provided with tappings, the voltage of the load circuit being regulated by interposing a pair of electric valves reversely connected in parallel in each of the connections to the transformer tappings, the conductivity of the valves being controlled by means responsive to the voltage of the load circuit. In the arrangement shown in Fig. 1, the transformer 13 has separate primary and secondary windings, tappings 14, 15, 16 on the latter being connected to the load circuit 11 through pairs of valves 17 .. 22 reversely connected in parallel. The valves are preferably of the vapour electric discharge type, and are provided with grids which are excited from the polyphase secondary winding 24 of a potential regulator through grid transformers 25, 26, 27. The primary winding 23 of the regulator is energized from the load circuit 11 and its position relative to that of the secondary winding is adjusted in accordance with the voltage of the load circuit by means of a motor 28 with reversing field windings 30, 31, the motor being adapted to rotate in one or the other direction in response to a voltage coil 34 connected across the load circuit 11. If the voltage of the load circuit varies from the normal value, the circuit of one of the field windings is closed, and the motor rotates in a direction to vary the phase relationships of the voltages applied to the grids of the valves in such a manner that the load circuit is transferred to the appropriate tapping of the transformer 13. In a modified arrangement, Fig. 2, the supply circuit 10 is connected to the load circuit 11 through an autotransformer 70, having two secondary taps 71, 72 in addition to the common connection between the circuits. Each tap is connected to the load circuit through a pair of reversely connected valves, the grids of the valves 73 .. 76 being excited from the secondary windings 78... 81 of a grid transformer 77, the primary winding of which is connected across one diagonal of a voltage responsive bridge, with resistances 84, 85. having large current-resistance characteristics in two of its arms. The other diagonal of the bridge is connected across the load circuit 11. With this arrangement, the voltages supplied by the taps 71, 72 are respectively below and above the desired voltage of the load circuit, and the load current is continually transferred from one tap to the other, the relative durations of the periods during which it is supplied from each tap determining the .average voltage of the load circuit. In another arrangement, Fig. 3, the supply circuit 10 is connected to the load circuit 11 through an autotransformer having a main winding 35 and a combined buck and boost series winding 36, the latter winding being connected across a bridge comprising valves 41 .. 48 arranged in pairs reversely connected in parallel. The control grids of the valves may be excited by an arrangement similar to that shown in Fig. 1, with the exception that a two-phase secondary winding is used, the grids of the valves of opposite arms of the bridge being excited from the same phase. In a modification of this arrangement separate bucking and boosting transformers are used.