GB126271A - Improvement in Method of Electric Arc Welding, Cutting and Repairing. - Google Patents

Abstract

126,271. Holslag, C. J. April 30, 1918. [Convention date]. Heating by electricity.-Arc welding, cutting, and repairing of steel, cast iron, copper, aluminium, &c. is effected by the use of alternating current, the pressure of which changes suddenly from a prolonged maximum of one polarity to a similar maximum of the other polarity, the work forming one electrode. A transformer may be used which produces two or more pressures simultaneously, the phase relation of which changes with formation or alteration of the arc, so that constant energy consumption is maintained. The transformer mav have a closed core, Fig. 1, on one limb of which the primary coil and main secondary coil are wound intimately together. An auxiliary secondary coil is placed on the opposite core limb and connected in series with the main secondary coil. Between the remaining core limbs 1 is a movable limb 15 adjustable laterally by a screw 19 and hand-wheel; this limb is slightly spaced from the outer limbs 1 by brass springs. Alternatively. the limb 15 may be drawn in magnetically against the action of a spring and dash-pot, to reduce the electric pressure after starting. Tappings 12, 13 are provided on all three coils, for varying the connexions. The electromotive forces in the two secondaries give a resultant which rises if the arc is obstructed by oil, slag, or dirt. If two or more arcs are in series, the back E.M.F. due to rupture of the arcs may be taken up by an inductance shunting the electrodes. Or the transformer may have a narrow additional limb wound reversely to the others in the secondary circuit. For polyphase currents, there are employed two or three transformers with their secondaries in series. The primary windings of two transformers may be independently connected to two-phase conductors; the transformers may be combined in one structure. A three-phase arrangement with primaries connected as in a Scott transformer is shown in Fig. 5. In another three-phase arrangement, with two transformers, the primaries are connected in open delta fashion. In a threephase arrangement with three transformers, the primaries are star connected but with one reversely wound. Bare or covered metal electrodes may be used. Specifications 120.886 and 142,521, [Class 38 (ii), Electric currents, Converting &c.]. are referred to,