GB559081A - Improvements in and relating to electric control systems for electric valve apparatus arranged for interconnecting a supply and a load circuit - Google Patents

Abstract

559,081. Automatic control systems for welding &c. circuits. BRITISH THOMSON-HOUSTON CO., Ltd. June 29, 1942, No. 8947. Convention date, July 1, 1941. [Class 38 (iv)] Current.-Current supply to a load circuit intermittently supplied through valves is rendered independent of changes in source voltage by a parallel connected auxiliary circuit having characteristics similar to the load circuit and supplied also through valves. Current in a welding circuit 13 fed through ignitrons 14, 15 having trigger valves 19, 20 which are controlled by compounded voltages derived from a peaking transformer 29a, a hold-off bias transformer 25 and an oppositely acting transformer 28 controlled by a timer 31 is controlled by one phase of the voltage applied to the primary winding of the peaking transformer. Valves 40, 41 controlled by the same transformer connect the source to an auxiliary load comprising inductance 38 and resistance 39 simulating the characteristics of the welding circuit. Voltage changes occurring across the resistance 39 cause a corresponding change in voltage across a resistance 76 which varies the grid voltage of a valve 62 controlling the saturating winding of an inductance 59 in a static phase shifting circuit supplying the primary winding of the peaking transformer to correct the current in welding and auxiliary circuits. An anti-hunting voltage is produced in the control circuit of valve 62 by a resistance-condenser circuit 71 across the saturating winding.