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The electric arc welding is the welding process which uses electric arc to create heat to melt and join the metals. In the electric arc welding, the electric power supply creates an electric arc between the electrode and the base material.
Depending upon the type of power supply used, the electric arc welding equipment is classified into two sections as −
The various equipment required for the electric arc welding (AC and DC) are shown in the figure and described below.
The welding machine used for electric arc welding can either be an AC or DC welding machine.
The AC arc welding machine has a step-down transformer to reduce the input supply voltage of 220 V to 80 V. The AC arc welding machine works with the power supply of frequency 50 Hz or 60 Hz. The efficiency of the AC welding transformer varies from 80% to 85% and the energy consumed per kg of depositis about 3 to 4 kWh. Although the AC welding machine has low power factor about 0.3 to 0.4.
The DC arc welding machine commonly consists of a motor-generator set. Where, the motor is a squirrel cage induction motor and the generator is the differential compound DC generator to give drooping characteristics. The source of DC power may also be an engine driven generator or transformer-rectifier welding set. In case of DC arc welding machine, the energy consumed per kg of deposit is about 6 to 10 kWh and the output voltage of the DC arc welding machine may be varied between 40 to 80 Volts and the current from 30 A to 300 A. The motor used in the DC arc welding has a power factor of 0.6 to 0.7.
The electrode holder is the equipment used for holding the electrode at a desired angle. The electrode holders for arc welding come in different sizes depending upon the current rating from 50 A to 500 A.
The cables or leads carry the electric current from the welding machine to the work-piece. The cable used for welding process are made of copper or aluminium and are flexible. The cables used for electric arc welding are made of 1000 to 2000 very fine wires twisted together so that the cables have flexibility and greater mechanical strength. The cable wires are insulated by a rubber covering.
The cable connectors are used for making the connection between machine switches and welding electrode holder. Generally, the mechanical type connectors are used because they can be assembled or removed easily. The cable connector for welding processes are designed according to the current rating of the cable used.
