Electric arc welding -: In welding generation of heat by an electric arc is one of the most efficient method. Approximately 50 % of the energy is libera-ted in the form of heat produced by the electric arc to fusion matelic peices. This is one of the most widely used method mainly because of the edge of use and high produc-tion rate that can be achieved economically.
The main requirement in electric arc welding set-up is the source of the electric power. They are two types-:
1. A.C. machine-:
( a ) Transformer
( b ) Motor or engine drive alternater
2. D.C. machine -:
( a ) Transformer with D.C. rectifier
( b ) Generater
The transformer does not have any moving part and as a result, oprate with less maintaness cost.
In A.C. welding normally only transformer are used. And in D.C. welding a rectifier or generator can be used to supply the required D.C. power.
A tipical A.C. arc welding set-up using the transformer is show in fig. The work peice is kept on a machine table to which the ground lit of the secondary winding of the welding transformer is connected. The other lit of the secondary winding is connected to an elect-rod holder into which electrod is crriped. When electrod is brought into connecte with the path welding takes place.
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