GB565602A - Improvements in electric valve systems for energising a load circuit through a capacitance and transformer - Google Patents

Abstract

565,602. Supply and control systems for resistance welding. BRITISH THOMSON-HOUSTON CO., Ltd. Feb. 19, 1943, No. 2794. Convention date, Feb. 28, 1942. [Class 38 (iv)] Thermionic control.-A welding or other load circuit is supplied with impulses of energy derived from an A.C. circuit 6 through a capacitance 5 which is discharged in alternate senses through the primary winding of a transformer 2 by pairs of controlled valves, such as ignitrons 22, 25 and 23, 24, the conductivities of the pairs being selectively controlled. A pair of reversely connected valves, such as ignitrons 101, 102, are also connected across the primary winding to prevent substantial reversal of the polarity of the capacitance at the end of each impulse. Each of the aforesaid valves may be ignited by a control valve in series with each ignition electrode and timing means associated with a valve 86 may be arranged to produce a periodic voltage to control the periodicity of the energization of the load circuit, other timing means 41 controlling the alternate selective operation of the valve pairs 22, 25 and 23, 24. The conductivity of the valves 102, 103 may be controlled by a transformer 106 in parallel with the transformer 2 having oppositely poled secondary windings each connected to the grid of a control valve 104, 105 through a circuit comprising a capacitance such as 115 and a resistance 114 to produce a voltage tending to maintain the control valves conductive selectively in response to the direction of current flow through the primary winding of transformer 2 and into the region in which the polarity of the capacitance 5 tends to reverse. The remaining supply and control arrangements shown in the Figure are described in Specification 563,531 to which the present Specification refers.