GB917688A - Improvements in and relating to electronic servo-regulating systems - Google Patents

Abstract

917,688. Control of D.C. motors. JELINEK, J. Aug. 14, 1959 [Sept. 3, 1958], No. 27930/59. Class 38 (3). [Also in Groups XXXV and XXXVI] An electronic servo-regulator for controlling the movement of a motor in both directions comprises two similar RC integrating circuits whose charges are controlled by e magnitude to be measured or regulated and a comparative magnitude, respectively, and two similar monostable electronic-trigger circuits connected respectively to the integrating capacitors to control corresponding thyratrons or tacitrons in turn controlling the direction of rotation of a servomotor, the outputs of both trigger circuits being connected through a double cathode follower to a pair of thyratrons coupled to discharge the integrating capacitors so that the thyratrons are non-conducting if none or one of the trigger circuits is operative, but both thyratrons fire when both trigger circuits are operative. In an integrating servomotor regulating system, voltages 1, 2 are applied over integrating RC circuits 3, 5 and 4, 6 to the grids of triodes 7, 8 and 7<SP>1</SP>, 81 having common cathode resistances 9, 9<SP>1</SP>; the anodes of 7, 7<SP>1</SP> being coupled to the grids of 8, 8<SP>1</SP>, respectively through parallel RC circuits and triodes 7, 7<SP>1</SP> being initially cut off while 8, 8<SP>1</SP> conduct. Excess of input voltage over a control value triggers 7 or 7<SP>1</SP> to conduct and 8 or 8<SP>1</SP> to cut off so that a positive pulse is applied over resistance 19 or 21 to trigger thyratron or tacitron 15 or 16 to fire from A.C. or half-wave rectified A.C. source 17 so as to energize servomotor 18 to rotate in one direction or the other to adjust either input voltage in a direction towards equality with the other, which may be a standard. The anode pulses from triodes 8, 8<SP>1</SP> are amplified by cathode followers 29, 30 having a common load 28 to apply a combined voltage over resistances 33, 34 to the grids of thyratrons 31, 32 such that the latter fire after the receipt of the firing pulses of both thyratrons 15, 16 to discharge integrating capacitories 5, 6. The cycle is repeated continuously until the input voltages are restored to equilibrium at equality. The input voltages may be derived from a tachometer generator or potentiometer, or from a phase discriminator. Alternatively, the input voltages may be equal and the servomotor may be applied to adjust one of the resistances 3, 4 of the input integrating circuits to equality with the other, one resistance may be a standard and the other a photo-cell or thermistor. The operation of the trigger circuits may be balanced by returning the grids of triodes 8, 8<SP>1</SP> to the ends of a variable potentiometer whose slider is earthed (Fig. 2, not shown), or by feeding the anodes of triodes 7, 7<SP>1</SP> from the ends of a similar potentiometer whose slider is connected to the H.T. supply (Fig. 3, not shown). Cathode followers may be interposed between triodes 8, 8<SP>1</SP> and thyratrons 15, 16, respectively (Fig. 4, not shown). A mathematical discussion and a graph of the system operation are given (Fig. 5, not shown).