Comparison between AC and DC Arc Welding Machine

AC Arc Welding Machine

DC Arc Welding Machine

 Striking of arc with electrode is relatively difficult maintenance of a short arc is also difficult except with iron powder electrode.

Developing an arc is easier maintenance of short arc is also easier.

 No problem of arc blow in AC arc welding machine. Work piece do not get magnetized in DC.

Arc blow is a serve problem and minimised with the use of proper corrective measure. Work piece may get magnetized due to current flow in one direction.

Arc is never stable.

Arc is more stable.

No polarity change possible and hence no suitable for welding all metals. It is used for welding ferrous metals.

Polarity (DCSP or DCRP) can be changed and hence suitable for welding both ferrous and non-ferrous metal s quality efficient.

More suitable for higher current value. It is less suitable for use at low current value with small dia of electrode.

It is most suitable with lower current value is also, for example at low amperage with small diameter electrode.

Bare electrode cannot be used. Only flux coated electrode with arc stabilizing agent influx can be used.

Bare and coated electrode can be used.

Not suitable for thin sheets or sheet metal work due to difficulty in striking the arc.

It is suitable for welding of sheet metal as striking arc is easier and arc remains steady.

Distribution of heat in arc is equal at electrode and job.

Most of heat (upto 66.67%) is liberated in the positive side of arc i.e. DC RP.

Voltage drop in welding is less and hence welding is suitable for longer distance from welding plant using long welding lead.

Voltage drop is relatively higher and hence start cables are used to weld only close to the welding plant.

Welding transformer has no moving part and working is salient.

A DC generator set has several moving parts therefore operation is noisy.

AC transformer welding set is not costly, simpler in operation maintenance cost is also very low.

A dc generator set is costly, difficult to operate and very high maintenance cost.