GB436811A - Improvements in and relating to control apparatus for electric discharge devices - Google Patents

Abstract

436,811. Switching-systems for consuming devices; valve circuits. BRITISH THOMSON - HOUSTON CO., Ltd., Crown House, Aldwych, London. July 23, 1934, No. 21507. Convention date, July 26, 1933. [Class 38 (iv)] [See also Group XL] In a system in which a load is switched on by operation of a relay 10 controlled by a grid controlled arc rectfier 7 whose anode circuit is supplied with A.C. in phase opposition to control A.C. applied to the grid thereof, control of the rectifier 7 is effected by a superposed pulsating voltage obtained from across a reactance 31 in the circuit of a grid controlled thermionic valve which is supplied with A.C. and controlled by a variable impedance 35, so that on the occurrence of a predetermined decrease in the value of the impedance 35 the arc rectifier 7 is rendered conductive. Means such as a reversing switch 14 and a phase splitting circuit 20, 21 are provided to alter the phase of the control A.C. voltage applied to the grid of the rectifier 7 relatively to the anode voltage and the polarity of the pulsating control voltage so that the valve 7 may operate on a predetermined increase or decrease in the value of the impedance 35. The variable impedance 35 may be a light-sensitive cell and the relay 10 thus operates either on a predetermined increase or a predetermined decrease in the illumination on the cell 35, according to the position of the switch 14 which causes a 90‹ phase shift of the A.C. control voltage and a reversal of the variable pulsating control voltage applied to the grid of the rectifier 7. Specifications 319,286, [Class 39 (i)], 357,572, [Group XL], and 403,987 are referred to.