Not All Constant Voltage is Equal

Constant Voltage (CV) is the most common output for wire processes, but both Miller and Lincoln sometimes use the term loosely. The Miller Bobcat volt-amp curve (Figure 1), for example, looks nothing like a traditional CONSTANT VOLTAGE volt-amp curve. It looks more like a CONSTANT CURRENT (for SMAW and GTAW) “Drooper” curve.

That is, large voltage swings for minor amperage changes (Figure 1) are not characteristic of a CV power source and will not provide a great arc (especially for MIG wire).

Figure 1

The Miller Trailblazer

The Miller Trailblazer, on the other hand, is a true CV machine. Its volt-amp curve (Figure 2) shows stable or constant voltage even with significant swings in amperage. This is the primary reason the arc from the Trailblazer is so much better for wire processes than that of a Bobcat. Likewise, the Lincoln Ranger 225 and the Lincoln Ranger 250 GXT are not true CV machines whereas the Lincoln Ranger 305 is.

Figure 2

So, not all “CV” is CV. If you want the best arc when running wire on an engine drive, consult a General Air sales associate. We will get you true CV Machine options.

Author: Bob Page