GB833985A - Improvements in or relating to electric arc welding - Google Patents

Abstract

833,985. Welding by fusion. BRITISH OXYGEN CO. Ltd. May 7, 1956, No. 15584/55. Class 83 (4). [Also in Group XXXV] In an electric arc-welding apparatus using a continuously fed electrode, the arc voltage is automatically maintained constant by a saturable reactor to stabilize the arc. In one embodiment, Fig. 1, the electrode E is supplied from the secondary of a transformer TW in series with a saturable reactor L. The reactor has one control winding energized from the A.C. mains via rectifier W1 so as to provide a substantially constant reference, and the other control winding energized in opposition by the arc voltage rectified at W2. In another embodiment, Fig. 2, the saturable reactor LP is in series with the primary of the welding transformer TW. One control winding B is energized by rectified mains voltage and the other control winding C is energized in the same sense by the rectified output of a current transformer TC in series with the arc so that an increase in arc current produces a compensatory increase in arc voltage. A voltage responsive relay has contacts S which short out a resistor R1 in the reference circuit to provide a high output for striking the arc. It is stated that the supply may be rectified to supply a D.C. arc, and that the signal controlling the reactor may be amplified. According to the Provisional Specification the reactor may have a core movable by a thyratron-controlled motor in accordance with the amplified arc voltage error. Coated electrodes or bare wires in conjunction with shielding gas or powdered flux may be used. Emissive coatings of say barium salts, thoria or zirconia may be applied to the electrode or workpiece.