GB436249A - Improvements in and relating to electric regulating systems - Google Patents

Abstract

436,249. Automatic regulation. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. July 2, 1934, No. 19493. Convention date, July 1, 1933. [Classes 38 (ii) and 38 (iv)] The current to a load having a negative volt-ampere characteristic is supplied and maintained constant through an arrangement comprising a pair of electric valves having discontinuous grid control and means to apply to the grid of each valve when non- conducting, superimposed upon a constant positive bias, a negative potential dependent in amplitude upon the load current. The gaseous discharge lamps 10, 11, 12, 13, are supplied from a source 14 through the supply transformer 18, a smoothing reactor 20, and a pair of electric valves 21, 22. A resistance 23 is also included in the system, its mid point being connected to the tubes 10-13. The primary winding of a transformer 25 is connected across the resistance 23, and its secondary winding has its ends connected through current limiting resisters 24 to the grids of the discharge valves. A capacitor 27 is connected across the secondary of the transformer 25, a positive bias potential is produced across a capacitor 26 in the grid circuit from a tertiary winding 28 of the transformer 18 a potentiometer 29 and a rectifying bridge 30. If for example, the load current tends to increase, the moment in each half cycle when either of the grids becomes positive is delayed, and the delay in the starting of the conduction of the tube automatically reduces the average value of the current. In a modification shown in Fig. 3, the alternating component of control potential is provided by a resister 23a energized by a current transformer 32, and amplified variations are produced in the positive bias potential. The positive bias capacitor 26 is energized from the circuit 14 through a rectifier bridge 30 and a transformer 33, and a saturable reactance device 34 is connected across the A.C. side of the rectifier 30. The saturating winding 35 is supplied through a rectifier bridge 39 from a parallel circuit comprising a resister 36 and reactor 37 connected in parallel with a capacitor 38, fed from the current transformer 32. The reactor 37 is self saturating and relatively small variations in load current produce large variations in potential across the saturating winding of the reactance device 34 and effects variations in the positive bias potential. Reference has been directed by the Comptroller to Specifications 362,364 and 370,405.