GB578901A - Improvements in generators of large pulses of electric current - Google Patents

Abstract

578,901. Supply systems for resistance welding. GENERAL ELECTRIC CO., Ltd., and FRIEDLANDER, E. July 12, 1944, No. 13317. [Classes 38 (ii) and 38 (iv)] A pulse generator, e.g. for welding operations, comprising a rectifier 10 which is supplied through a transformer 11 from an A.C. source and which is adapted to supply D.C. to the primary 16 of an output transformer 17, the secondary winding (not shown) of which supplies the current pulse to the load on current variation in the primary is characterised by the fact that the rectifier transformer 11 is tuned to resonance at the frequency of the A.C. source and thus serves as an energy-storing device, and also by the fact that control means are operable for " making " the D.C. circuit between the rectifier and the output transformer 17, thereby causing the stored energy to be applied to the transformer 17 as a pulse. The primary windings 12 of the rectifier transformer are connected through condensers 13 to obtain the required resonance. A group of auxiliary anodes 19 is connected through auxiliary secondary windings 20 and a choke 21 to an auxiliary primary winding 22 of transformer 17, the other terminal of which winding is connected to the rectifier cathode 18. This auxiliary primary 22 keeps the core of the output transformer almost completely saturated until the pulse is applied, when the core becomes saturated in the opposite sense, so that the flux alteration is substantially twice the saturation flux. The control grids 23 are normally supplied from the negative side of a battery 26, but when a pulse is desired, a source of positive grid bias 25 is inserted in series. This may be achieved by opening a switch 24, or, if periodic pulses are desired, by the circuit shown in Fig. 2, so that as the voltage increases in the primary 12, the D.C. output of rectifier 27 increases rapidly until the grids 23 become positive, at which point the main rectifier 10 operates, thereby supplying a pulse to transformer 17 and allowing the voltage in the primary 12 to fall.