GB811017A - Improvements in automatic voltage regulators - Google Patents

Abstract

811,017. Automatic voltage control systems. FOSTER TRANSFORMERS Ltd., and THOMAS, P. G. Feb. 8, 1957 [Feb. 14, 1956], No. 4566/56. Class 38 (4). An automatic voltage regulator consists of a buck/boost transformer T2 energized by a variable output transformer T1, the connections to transformer T2 being reversed in sense at the low limit of transformer T1 so as to double the range of regulation by changing from buck to boost or vice versa. The variable output transformer T2 is energized from the output terminals O of the regulated A.C. supply, and the output tapping is controlled by a reversible 2-phase servomotor 1. The motor 1 has a reference field 2 and a control field 3 fed from an auxiliary A.C. source, the supply to the control field 3 being reversible in sense by a centretapped supply transformer T3 and a pair of switching thyratrons 4, 5 which are selectively fired according to whether the output voltage of the regulator is high or low (by undisclosed apparatus). If, for example, the voltage is high, valve 4 conducts and motor 1 drives the transformer T1 towards minimum to reduce the boost voltage. At minimum, limit switch S1 is closed thereby energizing relay S5 which holds in over contacts S53 and changes over contacts S51 and S52 thereby reversing the sense of the supply to transformer T2 and reversing the direction of motor 1 so that continuing conduction of valve 4 results in an increasing bucking voltage. If the " raise voltage " valve 5 conducts, then relay S3 is energized to prepare a path over contacts S31 to short out and release relay S5 when the limit switch S1 is closed thereby restoring the original " boost '' connections.