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.