Power Sources for Gas Metal Arc Welding

The power for the arc welding processes can be either generated at the point of use or converted from the available electrical mains at the place of use. The power source for the GMAW is normally a constant voltage (CV) or constant potential (CP), flat characteristics type machine which supplies DC current. The welding gun is connected to the (+) pole, while the work piece is connected to the (-) pole. Wires above 2 mm. in diameter could also be weld using a constant current (CC) power source.

Generally, welding power sources are classified according to the type of welding current they produce. The most popular GMAW power sources are the transformer rectifier types, where the power from the mains is first transformed to the required voltage by a transformer and than rectified to DC. These power sources are more efficient than motor generator types and their operation is quieter.

The most widely used type of power source for this process is the three phase transformer rectifier with a constant voltage characteristic. The three phase input power produces a stabler arc and avoids line unbalance which occurs when a single phase power source is used. The full wave rectified DC output obtained with a three phase power source produces a very smooth weld.

The motor generator GMAW power sources are mainly used when there is no other available source of electrical energy. These machines are noisy and therefore not suitable for indoor operation. Their maintenance cost is higher and their economical life is shorter than that of transformer rectifier power sources.

Constant current (CC), dropping characteristic welding power sources are not popular for GMAW. They can be used for GMAW operations only when large diameter wires or flux cored wires are used. CC power sources are used for submerged arc welding.