GB650185A - Improvements in or relating to electric welding systems - Google Patents

Abstract

650,185. Supply systems for welding arcs; protective arrangements; automatic regulation; inductances. GENERAL ELECTRIC CO., Ltd., and FRIEDLANDER, E. S. May 25, 1948, No. 14141. [Classes 38 (ii) and 38 (iv)] In a direct current arc - welding system which is adapted to supply the arc from an A.C. souce 2, through rectifying means such as dry-plate rectifiers 4, a saturable reactor 8 is included in an A.C. supply lead and has a control winding 13 energized with D.C. derived from a saturable current transformer 10 also included in an A.C. supply lead and which is unsaturated when no welding current is flowing and is substantially saturated for all values of welding current so as to provide substantially constant excitation to winding 13 whilst welding to ensure that the open circuit voltage across the rectifier is little, if any, higher than it is on load. The arc may be stabilized by including a further control winding 15 on the reactor, assisting winding 13, and which is energized according to the direct welding current. The rectifier may be supplied through a transformer 3 in which case the saturable reactor 8 is preferably included in the primary circuit with the current transformer 10 included in either the primary or secondary circuit of transformer 3. Winding 13 is preferably included in series with an adjustable resistance 14, to vary the welding current and energized from the transformer 10 through a further rectifier 12. Fig. 2 (not shown) shows a system for operation from a 3-phase A.C. supply and including a 3-phase saturable reactor which may comprise (Fig. 3) a pair of three-legged laminated core-parts 37 disposed side-by-side and bridged by a pair of yokes 38 which may be solid, and providing air gaps 39. The opposite limbs of the two core-parts 37 respectively carry one of two parts of a winding 22 included in an A.C. supply lead, the control winding 31 carrying all or a fraction of the load current is wotmd in two parts, one round the whole of each core-part 37, and the main control winding 35 energized from the current transformer is also in two parts, each part being wound around each yoke 38. Specification 618,630 is referred to.