Electrical news and engineering . odes and metalbeing welded. On account of the extent of the reach thesecondary circuit becomes a reactance loop of greater orless length, see Fig. 1. Due to the large currents in thisloop the reactance becomes an objectionable feature and,in order to overcome this difficulty, the duplex-spot welderwas brought out. In the duplex-type of welder, Fig. 2, the secondary re-actance loop is reduced to a minimum and is independent ofthe reach of the machine. Two complete identical equip-ments are placed, one above and one below, the plates beingwelded. Each equipment
Electrical news and engineering . odes and metalbeing welded. On account of the extent of the reach thesecondary circuit becomes a reactance loop of greater orless length, see Fig. 1. Due to the large currents in thisloop the reactance becomes an objectionable feature and,in order to overcome this difficulty, the duplex-spot welderwas brought out. In the duplex-type of welder, Fig. 2, the secondary re-actance loop is reduced to a minimum and is independent ofthe reach of the machine. Two complete identical equip-ments are placed, one above and one below, the plates beingwelded. Each equipment has two parallel electrodes andcontains one half of the secondary loop. The upper elec-trodes are brought down on to the work in such a positionthat they are directly opposite the electrodes of the lowerequipment. The secondary currents then circulate down-wards through the plates on one side and up on the otherside, thus giving higher efficiency by avoiding a long loopwith its additional resistance and reactance. Also, while the. Fig. 2—Duplex Spot Welder—Minimum reactance in loop equipments are identical, currents of any appreciable valuewill not pass horizontally in the plates. Line welding is a branch of spot welding producing ajoint similar to a line of rivets, but stronger and water tight. Electric Fusion Welding Both welding and cutting by means of the electric arcwill be considered under this heading. In these processes,the electric arc is used merely for the production of a hightemperature ranging from 6300°F. to 7300°F. Arc welding is specially suited to such work as (.a* join-ing of plates or broken parts; (b) building up parts worn byuse: (c) filling blowholes in defective parts; (d) caulkingjoints. Before proceeding to make a repair or to build up wornparts by the electric arc welding process, the material must December 1, 1919 THE ELECTRICAL NEWS be prepared for the operation. All scale, grease and dirtmust be removed from the part on which the welding is to
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