The C & C system of electric arc welding has been developed during a longer period than any of the others, because the C & C Company is the pioneer in that field in America and, consequently, has its control system developed to a higher degree and protected by numerous patents. The welding machine consists of either a single-unit machine or dyna-motor for use on direct-current circuits, or a low-voltage compound-wound direct-current generator of high overload capacity direct-connected to a motor of proper size and suited to the power supply, both machines being mounted upon a substantial cast-iron base as indicated in Fig. 70. For controlling the motor and generator, a switchboard is supplied which may be mounted in any convenient position with relation to the machine and connected to the power circuit. On this panel are mounted the necessary instruments and switches for the welding machine and motor, and the apparatus for controlling the welding circuits is usually mounted upon separate smaller panels, although for portable equipments or single-circuit outfits everything is mounted on the main switchboard panel.
Fig. 70. 300-Ampere Welding Set with Control Panel and Auxiliary Welding Panola Courtesy of C&C Electric and Manufacturing Company.
Each welding-circuit control panel contains one of their patented automatic control outfits, and means are provided for preventing a rush of current when drawing the arc as well as for inserting a protective resistance to reduce the current in case of overload when using the graphite arc. By this means the thinnest metal, Fig. 71, or the heaviest castings, Fig. 72, may be welded safely and smoothly with equal facility, and the operation of the controlling devices is so entirely automatic that the operator does not have to go to the switchboard and close circuit breakers or other devices after once starting work. This system of welding has been developed for working by either the Benardos or Slavianoff process.
By referring to the diagram of connections, Fig. 73, it will be seen that the current flows from the positive side of the generator to the job, through the arc, electrode and holder, resistance, overload and series relays, and back to the negative side of the generator. The diagram shows the positions of the various items before the arc is drawn, and it will be noted that all of the resistance is in series with the electrode and other devices. The arc will, of course, be drawn between the electrode and the work in the usual manner, and it will be noted that the coil on the magnetic contactor is so connected as to be in shunt or parallel with the arc. When contact is made between the electrode and work to establish the flow of current and strike the arc, the coil of the series relay will be energized and it will close and energize the coil of the magnetic contactor. The contactor will not close, however, until after the electrode has been removed from contact with the work and the arc formed, because that contact is of lower resistance than the coil in shunt with it. So long as the magnetic contactor is open, all of the grid resistance is in circuit and the flow of current is too small to burn the work or overload the generator. As soon as the arc is drawn, that path becomes of higher resistance than the path through the shunt coil on the contactor, hence the magnetic contactor coil gets current enough to close the contactor and cut out resistance until enough current flows to suit the job in hand as predetermined by the setting of the resistance switch. In case of overload while working, the overload relay open-circuits the coil of the magnetic contactor and causes it to open and re-insert the entire resistance, cutting the current to the minimum without rupturing the arc.
Fig. 71. Miscellanaous Pipe Weld with Light Tubing Courtesy of C & C Electric and Manufacturing Company.
Fig. 72. Broken Steel-Forged Crankshaft Welded with Graphito Electrode Courtesy of C&C Electric and Manufacturing Company.
Fig. 73. Wiring Diagram for C & C Welding System.
Owing to the use of a separate panel for each welding circuit, it is possible to have as many operators working at once as conditions require, tapping the panels off the distribution circuit from the machine panel the same as would be done with so many motors from any other circuit. The only limitation is that the generator shall be of sufficient capacity to furnish the current required. Another feature of this system lies in the use of an automatically self-closing overload circuit breaker on the main control panel for the motor, thus restoring the motor circuit automatically after the overload on the welding circuit or generator is removed. These outfits are also made portable, as shown in Fig. 74.
Fig. 74. 600-Ampere Portable Single-Unit Welding Outfit Courtesy of C & C Electric and Manufacturing Company.
In addition to the constant-voltage apparatus just described, the C & C Company also makes a variable-voltage welding outfit for use when but one operator is to work from the machine. This consists of a differentially-wound compound-generator driven by a suitable motor, with proper controlling devices mounted upon a switchboard panel. With this outfit work is done with as low as 12 volts drop in the arc and at a very high efficiency. The generator voltage varies automatically to keep the current constant at the predetermined value, regardless of the arc-length.
This company has recently brought out a machine to replace that formerly handled by them, based upon the use of a compound-wound generator of the variable-voltage constant-current type having an auxiliary exciter. This exciter is provided with a special differential winding, which changes the voltage supplied to the main generator field. Therefore, the action of the welding current in the end automatically regulates the voltage of the main generator so as to keep the current constant and at the predetermined value regardless of variations in the resistance of the welding circuit. The proper current for the work in hand is obtained by regulating the field of the machine before starting work, after which it is kept constant by the machine. Owing to the use of low voltage (usually between 10 and 20 volts with a maximum of 30 volts) the efficiency is considerably better than machines operating at higher voltages, and machines of this type are coming into greater use where but one man is to work from a machine. It is impossible to work two or more men at once from apparatus of this type, multiple-circuit outfits always being of the constant-voltage type with resistance in each circuit to vary the current. Variable-voltage generators are driven by suitable motors and have the controlling devices on switchboards in the usual manner. Of course, with this system, no resistances are required.
The equipment offered by this company has lately been placed on the market and consists of the usual low-voltage machine with welding circuits containing regulating resistances, similar to those described for the Westinghouse and Lincoln outfits.
An English system known as the "quasi-arc-method of welding" has been used to a limited extent abroad, but has not been received very kindly in America because of the expensive electrodes used. This is based upon the use of wires or electrodes coated with a flux for preventing oxidizing.
The Kjellburg system is also based upon the use of a flux on the wire and the users of it make some very strong claims for it, but experience shows that work can be done satisfactorily without flux for every kind of welding. With both of the above types of electrodes, any of the apparatus described may be used.