A.C. Welding Sets and Methods of AC Welding

Welding transformer:

Single phase or three phase step down transformers are used. The transformer is designed for high leakage reactance. The secondary voltage on open circuit is about 80-100 volt. Some control device is also used along with this transformer.

The secondary winding is air cooled and made up of copper strip. Oil cooled transformers are also used.

The air cooled sets are cheaper in cost and lighter in weight and easier to maintain. It can be easily shifted from one location to other.

Oil cooled sets are more compact but these are heavy so suitable for stationary application, e.g. in workshops.

The current control in welding transformer can be obtained by following ways:

(i) Tapped reactor method :

A series reactor is used with tapping on it fig.(a)

(a) Tapped Reactor Method

The output current can be varied by selecting appropriate tap. Different values of currents can be obtained by this method.

(ii) Moving Coil Method:

The transformer used in shell type with a movable primary winding as show in Fig.(b)

(b) Moving Coil Method

The movement of primary is possible by rotating the handle. If primary is moved near to secondary the current increases and if it is moved away current decreases.

(iii) Magnetic Shunt Method:

A magnetic shunt is used to divert the flux. The position of magnetic shunt can adjusted. Hence, value of flux in transformer core changes and thus current can be changed. fig.(c)