GB514835A - Improvements in voltage control devices for electric supply systems - Google Patents

Abstract

514,835. Automatic control of electromotive force. WHITE, E. L. C. May 17, 1938, No. 14631. [Class 38 (iv)] In a voltage stabilizing system compensating for variations in the supply voltage and the load current, the positive terminals of the source of supply and of the load are directly connected, while the negative terminals are connected through a grid-controlled regulating valve acting as a variable impedance under the control of a controlling valve responding to the electromotive force across the load terminals. The positive terminals of the supply 5 and the load 6 are connected to one another and to earth, the negative terminals being connected through the regulating valve 11. The grid of this valve is negatively biassed and is connected to the cathode of the control valve 7 and thence to the positive terminals through a resistance 8. Battery 9 provides negative bias in the control valve 7. The arrangement is such that deviations from a predetermined value of the load 6 result in variations of the impedance of the regulating valve 11 tending to correct the deviation: Variations of the supply 5 above or below the usual value also vary the voltage difference between the cathode and the negatively biassed grid and result in variations in the impedance of the regulating valve tending to maintain the load at or near a constant value. In modifications, tetrodes or pentodes may be used and an additional battery may be arranged in series with the resistance 8. An additional controlling valve serving as an amplifier may be used, in which case only part of the voltage across the load may be applied to control the potential of the cathode of the controlling valve with respect to the grid. The source of negative bias 10 may be energized from an A.C. source and a rectifier.