Introduction to electric welding:
Welding is the process of joining two similar metals by heating. The metal parts are heated to melting point. In some cases the pieces of metal to be joined are heated to plastic stage and are fused together.
The electric welding sets may be either dc or ac type. DC welding sets are of two types namely generator type welding set consisting of a differential compound wound dc generator, giving drooping volt-ampere characteristic, driven by any type of prime-mover (a squirrel cage induction motor or a petrol or diesel engine) and dry type rectifier (selenium rectifier) used in conjunction with a multiphase high leakage transformer. IN generator type welding sets the control may be obtained by tapping the series field or by providing a suitable shunt across the series field winding. In the rectifier type set dc voltage is controlled by regulating the transformer output. If supply from existing dc distribution system is to be used for welding then ballast (resistance) is put in series with the equipment and the control is affected by varying this external series resistance.
In electric welding process, electric current is used to produce large heat, required for joining two metal pieces. There are two methods by which electric welding can be carried out. These are
a) Resistance welding and
b) Arc welding.