4.2.2 Power Sources
The power source used for SMAW is a constant current type, i.e., it has a drooping volt-ampere curve
(see Figure 4.4). With such a power source, the welder sets the required current at the power source
and the voltage is controlled by the arc length that the welder maintains during welding. The drooping
power source is preferred because there is a small but continual variation in the arc length due to the
manual nature of the welding process. This is reflected in a continual change in the arc voltage, but
due to the drooping characteristics of the volt-ampere curve the accompanying changes in the arc
current, and therefore the electrode melt off and deposition rates, are small. Figure 4.3 shows typical
SMAW power sources.