GB696743A - Improvements relating to apparatus supplying current to electric arcs - Google Patents

Abstract

696,743. Transformers; supply systems for welding arcs. METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. Feb. 22, 1952 [Feb. 23, 1951], No. 4759/52. Classes 38 (ii) and 38 (iv). [Also in Group XXXVI] A transformer supplying an arc welding load comprises primary and secondary windings 3, 4 on a core 7 and has two auxiliary windings 5, 6 associated with the primary and secondary windings respectively, and so connected that they generate fluxes in opposition. Upon energization of the transformer, relay contacts 26 are closed to connect resistance 27 across the series-connected auxiliary windings, a circulating current then flowing through the auxiliary windings and resistance 27, whereby the leakage flux of the transformer is reduced and the output current increased for a time depending on the delay setting of relay 25. At the end of the set time owing to the fall in output volts of the transformer upon load passing, contacts 26 open and the output current falls. The load may be drawn from terminals 17, 18 or 17, 19, the auxiliary windings being respectively independent of or in series with the secondary winding 4, the circulating current in the latter case flowing through the auxiliary windings in opposition to the load current which is in effect reduced in these windings. For energizing the relay, one of switches 29, or 30, must be closed, and special couplings whereby the appropriate switch is closed upon connecting the load to terminal 18, or 19, are described (see Group XXXVI). The primary winding 3 and auxiliary winding 5 may be moved together by rotation of handle 13 to vary the transformation ratio, which ratio is varied still further by the auxiliary windings, as described in Specification 551,709. The auxiliary windings may be connected in series with the primary winding 3, Fig. 3 (not shown).