Page 185 - Welding of Aluminium and its Alloys

168 The welding of aluminium and its alloys

9.2 Modern pedestal mounted spot welder for aerospace applications.
Courtesy of British Federal.

The spot welder may be pedestal mounted (Fig. 9.2) or portable. With
portable equipment the transformer may be remote from or incorporated
into the welding gun. With portable equipment the weight of the trans-
former makes the gun with the built-in transformer difficult to manipulate
even with counterweights to ease manual handling. The gun weight may
also exceed the carrying capacity of welding robots. Using a power source
remote from the gun requires heavy, stiff cables to deliver the welding
current, again making the gun difficult to manipulate.

9.2.2 Single phase DC units
Single phase DC units are rather more energy efficient than the single phase
AC units as rectification of the current in the secondary circuit reduces
losses due to inductance. Power demand across the phases is also more bal-
anced than the single phase units. Although the rectifier adds to the weight
the increased efficiency enables a lighter transformer to be used, giving an
overall reduction in weight. The equipment cost is greater than the simple