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.
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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. |

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