Power Supply for Resistance-Welding Machines

In the following representative welder installations, several types of feeder distribution systems are represented. Two of the companies employ a bus system to which the individual welders can be readily and quickly connected or disconnected. Tap points are available at regular intervals and the welding machines can be moved around from season to season with very little expense. The same is true, to a lesser degree, of the wire or cable feeders used by the other companies. This type of feeder does not lend itself quite so readily to frequent changes in plant layout, but is generally cheaper and easier to install. The bus system employing the concentric arrangement of copper tubes will be found to have the lowest voltage drop, and where this factor is of major consideration this type of feeder is of highest efficiency. In installations where the equivalent thermal loading is high, this type of construction may be unsatisfactory since the heat radiation or conduction from the inside conductor is comparatively low. However, should it become necessary, cooling air can be forced through the inner conductor thus raising its load capacity. The system of interlaced copper bus bars, usually has a high load capacity, but gives a slightly higher voltage drop than the concentric construction. The system of cable construction is of course the simplest, since the problems of insulation are minimized. In general this type of construction gives a higher voltage drop and lower load capacity than either of the above types.