GB672046A - Improvements in or relating to thermionic valve relay circuits - Google Patents

Abstract

672,046. Automatic voltage control systems. GENERAL ELECTRIC CO., Ltd., and MACKENZIE, R. B. Jan. 30, 1951 [Jan. 30, 1950], No. 2405/50. Class 38 (iv). [Also in Group XL (c)] A relay circuit comprises two valves cross connected as a trigger pair with an electromagnetic relay in the anode and cathode circuit of the two valves respectively so that when the input voltage applied to the grid circuit of one valve moves in one direction from a datum level the relay in the anode circuit is energized and when it moves in the other direction the relay in the cathode circuit is energized and the other relay released. The Figure shows a cross-connected pair of valves 8, 23 having a relay 20 in the anode circuit of valve 8 and a relay 24 in the cathode circuit of valve 23. An A.C. input voltage which it is requred to maintain constant is applied at terminals 1, 2 via two gas-filled constant voltage tubes 3, 4 to an input resistor 5. The voltage across resistor 5 is rectified by the rectifier 9 filtered in circuit 11, 11<SP>1</SP> and applied to trigger valve 8. If the input voltage rises above a predetermined datum level the anode current of valve 8 increases and relay 20 is energized, the fall in potential at the anode of valve 8 is applied to the control grid of valve 23 to reduce the cathode current in this valve and thus to release relay 24. If on the other hand the input voltage falls below the datum level the anode current in valve 8 falls and relay 20 is deenergized, the rise in the anode voltage of valve 8 causing increased cathode current in valve 23 so that relay 24 is operated. The circuit may be used to maintain the input voltage constant by using the contacts of relays 20, 24 to control the direction of rotation of an electric motor arranged to drive a circuit element to revert the input voltage to its datum level on departure therefrom. The variable resistors 21, 25 are coupled together to vary simultaneously but in opposite directions thereby enabling the sensitivity of the circuit to be varied.