GB875660A - Improvements in electric arc welding apparatus - Google Patents

Abstract

875,660. Exciting dynamo-electric machines; supply systems for welding arcs. LINCOLN ELECTRIC CO. Ltd. Jan. 24, 1958 [Nov. 8, 1956], No. 34173/56. Classes 35 and 38 (4). In an electric arc welding apparatus comprising means for producing a welding arc 6 and a generator for supplying the arc and having control gear, the generator field winding is separately excited and is divided into two or more sections 1, 2, and the control gear includes means for changing the connections to one of the sections whereby the sections may be changed from mutually additive to mutually subtractive magnetic effect in order to substantially reduce the generator output voltage while maintaining current through the field windings. The invention is to reduce output voltage variations as between when the generator is hot or cold, by keeping the field windings at a constant temperature regardless of whether the generator is idling or supplying welding current. As shown the changing means comprises a change-over switch 4 connected across the section 2 which is parallel connected with the section 1 which has a series-connected either fixed or variable resistor 5. Alternatively the sections 1, 2 may be mutually series connected, and they may have either equal or unequal magnetic effects to one another, the latter embodiment providing a voltage sufficient for adjustment.