GB595697A - Improved apparatus for electric arc welding - Google Patents

Abstract

595,697. Supply systems for welding arcs ; high-frequency apparatus. BAGNALL, R. I., LEGG, C. R. E., and FOSTER TRANSFORMERS & SWITCHGEAR, Ltd. May 7, 1945, No. 11560. [Class 38 (iv)] In an A.C. arc welding system fed from a low or mains frequency supply, stability of the arc at reduced supply voltage is effected (a) by additional windings on a regulating inductor which are energized inversely as the voltage across the arc and (b) by a high-frequency high voltage superimposed on the welding voltage. In the arrangement of Fig. 1, a variable inductor 6 connected in series with supply transformer 5 and the welding electrode 4, is provided with additional windings 15, energized by D.C., inversely as the supply voltage across the arc, from a metal rectifier 16 connected on the input side to the electrode 4 and workpiece 3. A high-frequency resonant circuit comprising capacitor 10 and inductor 11 is fed from sparkgap 9 connected across the high voltage secondary of transformer 8, the primary of which may be energized by the secondary voltage of supply transformer 5 or the voltage. across the inductor 6. A suitable impedance may be connected in series with the primary of transformer 8 and the inductor 11 may be coupled directly or inductively to the welding circuit. In another arrangement, Fig. 2 (not shown), one or more capacitors in the primary circuit of transformer 8 effect modification of phase difference between the primary voltage of this transformer and that existing across the arc. In both arrangements, a small capacitor 13 is connected across the welding circuit as shown to complete the high-frequency circuit through the electrode and work. Specifications 591,702 and 594,486 are referred to.