The equipment required for electric-are welding depends largely upon the nature of the work to be done but, of course, the most complete apparatus does the best work, as in the case of any other sort of apparatus. The most elementary equipment consists of a barrel of water with two iron plates in it (using the resistance of the water to reduce the amount of current flowing) and an electrode holder, with some cables to connect the parts to the power circuit. This system can be used for cutting and for welding where roughness and uncertainty of results are no disadvantage. The current is varied by varying the space between the plates in the water barrel but this system is very wasteful and inefficient because the line voltage (usually 220 volts in shops and 550 volts for street railways) must be cut down to that required for welding (about 25 volts in the arc); this is done by dissipating the unused energy in the form of heat in the water. Sometimes resistances, made up of cast-iron grids, Fig. 60, are used instead of the water barrel, but they are more expensive and just as inefficient. This grid resistance is cut into and out of circuit by a series of switches.
The use of dynamo-electric machines of low voltage. Figs. 58 and 70, instead of resistances as just described, is preferable because of their higher efficiency and the better voltage regulation obtained. Fig. 59 shows a typical wiring diagram for the low-voltage equipment. It is well known among electrical men that a properly designed motor-generator set gives the best regulation of voltage and, when the generator is properly compounded, we have the ideal apparatus for electric-arc-welding. The leading systems in general use today consist of motor-generator sets with suitable control apparatus for motor, generator, and the welding and cutting circuits.
Fig. 59. Elementary Low-Voltage Are-Welding Equipment.
Single unit machines such as dynamotors, synchronous converters, etc., are also used, although the voltage regulation and current control are not quite so good as with motor-generator sets. For working with the graphite electrode and for the heavier classes of metallic electrode work they are all right, and a large number of them are in use in foundries, ship yards, railway shops, etc. A few of them are also being used in lighter work where the total load is not such as to cause a drop in voltage, and they make fine portable outfits because of their small size and light weight.
There are at present only seven companies of importance in the United States offering electric-arc-welding outfits, six of which use low-voltage generators and the seventh furnishing iron-grid resistances to reduce the voltage to that required for welding. The C & C Electric and Manufacturing Company has been in the field 11 years; Westinghouse Electric and Manufacturing Company, 9 years; General Electric Company, 8 years; Lincoln Electric Company, 5 years; and the Burke Electric Company is just entering the field. These are the only companies manufacturing arc welders, although the Siemund-Wenzel Electric Welding Company is having apparatus made for it by the Crocker-Wheeler Company; the Welding Materials Company has its apparatus made by the Triumph Electric Company; and the Indianapolis Switch and Frog Company makes a resistance system, as stated. Each of these companies offers apparatus on the strength of some peculiarity of the controlling apparatus for the welding circuits or certain features of the welding machines.
Fig. 60. Portable Electric Welder in Action Courtesy of Indianapolis Switch and Frog Company.
The Indianapolis Track Welder, Pig, 60, consists of a group of iron resistance grids mounted in a framework on a four-wheeled truck, with means for making connection with the trolley wire to get current. It is used almost entirely for repairs on street railway tracks- The control device consists principally of a set of switches for varying the number of grids in series with the arc, an electrode holder and cables. The Slavianoff system is used for most operations, although the Benardos system may also be used. Owing to the low efficiency of operation they have not been adopted for use in industrial plants, but the cost is comparatively low and street railway companies do not seem to object to the enormous waste of energy incident to their use.
Fig. 61. Wiring Diagram Showing Principal Features of the Indianapolis Track-Welding System.
The diagram of connections, Fig. 61, shows the relation of the various parts of this equipment and the switches for varying the current by cutting in or out the grids of the resistance. The nature of this system, as with water barrels, is such as to necessitate a separate outfit for each operator in order that he can adjust his current to suit the work in hand without interfering with the other operators.