GB498210A - Improvements in and relating to electric valve circuits - Google Patents

Abstract

498,210. Converting; control systems for consumption apparatus. BRITISH THOMSON-HOUSTON CO., Ltd. Nov. 1, 1937, No. 29843. Convention date, Oct. 31, 1936. [Classes 38 (ii) and 38 (iv)] Thermionic and like control.- Comprises an excitatibn circuit for arrangements employing discharge devices for interconnecting A.C. and D.C. circuits and A.C. circuits of the same or different frequency, in which means are provided responsive to the decay of voltage between the anode and cathode of a device upon conduction commencing which injects a voltage into the excitation circuit to effect de-energization of the control electrode. The Figure shows an arrangement having valves 1-4 of the immersion-ignitor type for interconnecting A.C. networks 5, 6. The excitation circuit of each discharge device comprises a condenser 16 which is charged from a transformer 17 through an auxiliary rectifying valve 18 and resistance 19, and is discharged when an ignition impulse is required by means of a valve 20 through a transformer 24, the secondary of which supplies the ignitor electrode 10. The grids of the valves 20 are supplied from a phase shifting circuit 33 to determine the moment of ignition. As soon as conduction commences in a discharge device, the ignitor electrode is de-energized by means of a circuit 27 comprising a condenser 28 in series with a resistance 29 across the discharge device. The resistance 29 is also connected in the primary circuit of a transformer 30, the secondary of which is in the anode circuit of the valve 20 so that as soon as the discharge device 1 becomes conductive the condenser 28 discharges through the resistance 29 and injects into the anode circuit of the valve 20 a voltage which renders the valve non-conductive. The control impulses for the valves 20 derived from the transformer 35 may be peaky.