312 Electrical Power Systems Technology
are melted, creating a metal pool that is added to, when necessary, by the
use of a filler rod. The puddle (molten metal pool) then fills in the gap (arc
crater) that was created by the arc of the electrode. Various types and vari-
ous current-voltage ratings of electric arc welders are available.
A smaller amount of current is required for arc welding than for re-
sistance welding. The currents may range from 50 to 200 amperes, or high-
er for some applications. Voltages typically range from 10 to 50 volts. An
electric arc welder may be powered by a portable generator, a storage-bat-
tery unit, a step-down transformer, or a rectification unit.
Induction Welding
The induction welding process uses the principle of induction heat-
ing to fuse metals together. High-frequency AC is applied to a heating coil,
Figure 12-4. Resistance welding methods: (A) Spot welding, (B) Seam welding