GB780363A - Servo device - Google Patents

Abstract

780,363. Electric correspondence control systems. S.I.R.E.L.E.C.July 11, 1955, No. 20065/55. Class 40 (1).. In an automatically balanced differential potentiometer system the D.C. error voltage applied to terminals m, n (Fig. 3) is amplified by push-pull valves 10, 101, combined in transformer 14 with an amplified first derivative voltage obtained from potentiometers 12, 12<SP>1</SP> and fed to the centre points of the secondary windings of transformers 18, 181 with an alternating voltage on their primaries, so that when the secondary windings are connected to two push-pull amplifier valves 16, 161 and 17, 17<SP>1</SP> the anode currents consist of a train of pulses whose phase position relative to the alternating voltage is determined by the magnitude, rate of change and sense of the error voltage at m, n. A 90-degree phase shift with zero error voltage is obtained by R.C. stages 19, 191. The pulse trains are fed to the grids of two pairs of thyratrons 7, 8 and 71, 8<SP>1</SP> (Fig. 1) whose anodes are connected to the alternating voltage source, so that the anode currents passing through opposed field windings 9, 91 of a motor 4 determine the direction of rotation, and cause the motor 4 to adjust potentiometer 3 to rebalance the system.