GB618630A - Improvements in or relating to electric welding systems - Google Patents

Abstract

618,630. Supply systems for welding arcs; transformer systems. GENERAL ELECTRIC CO., Ltd., FRIEDLANDER, E. S., and DUNHAM, C. R. Nov. 6, 1946, No. 32954. [Class 38 (iv)] Where a welding arc is supplied through dryplate rectifiers, the voltage applied to the rectifiers is automatically controlled by the welding current or voltage so that at no load the applied voltage is not more than 50 per cent greater than when welding. The welding current; or a portion thereof, may control the impedance of an inductance in the supply circuit and a further control winding on the inductance may be responsive to the output voltage of the rectifiers. The controlled inductance may include that of the transformer. In another arrangement an inductance in each supply phase is controlled by the are voltage. Fig. 1 shows, in the primary circuit of a transformer 6, saturable inductances 9 with a D.C. magnetization responsive to the output current of rectifiers 3 supplying the welding electrode 5, and an adjustable current shunt 18. Fig. 2 shows the welding current arranged to excite a saturating winding 26 on the transformer, the core of which, together with that of an inductance 22, is adjustably premagnetized from a source-fed auxiliary rectifier 30; the windings 26, 27 oppose one another. The transformer saturation may depend on the opposed voltages of the arc and the auxiliary rectifiers (Fig. 3, not shown). Fig. 4 shows three inductances 48, in the primary circuit of a transformer having a zig-zag secondary winding, wherein mutually opposed saturating windings 52, 53 are excited, respectively, by a rectified voltage from the supply circuit which equals the average arc voltage, and by the difference between this voltage and the arc voltage, but only when the latter is the greater, thereby limiting the are voltage; this limiting value may be adjusted by resistances 56, 60. A third set of saturating windings opposing the windings 52 may be added to counteract the tendency for high output currents at low voltage, a rectifier 63 preventing reverse current in these windings.