electric current supply (continuous and alternative facilities of plasmas at high temperatures.

摘要

1476531 Plasma arc welding LA SOUDURE ELECTRIQUE AUTOGENE PROCEDES ARCOS SA 31 Dec 1974 [15 Jan 1974] 56123/74 Heading H2H A supply arrangement for a plasma welding torch using main and pilot arcs is arranged such that both arcs are energized from a single A.C. source, the main arc being A.C. and the pilot arc being D.C. As shown, a secondary 6 of a transformer has an end portion A, B centre-tapped at 7 and connected at its ends with two diodes 4, 5 which provide D.C. to produce a pilot arc between components 1, 2 of the welding apparatus. A.C. between lines 7, 8 is impressed across component 2 and the work 3 to produce the main arc. The value of the currents fed to the two arcs may be independently adjusted and a phase shift between the D.C. and A.C. currents introduced to maintain the main arc during A.C. zero crossings. Symmetrical end portions of the transformer secondary may be used to operate two plasma welders with their flames in opposition and a secondary associated with each phase of a 3- phase supply may drive one of 3 welders their flames joining at a point.