Improved series arc welder with wire speed controlling devices

摘要

The present invention relates to electric arc welders for depositing weld metal along a groove between two edges of a metal workpiece (WP). In particular, according to one embodiment of the present invention, a welder comprises: a leading electrode (EI) driven toward a point in the groove by a first wire feeder (400) operated at a first speed by a first motor (MI) with a speed control input and a tachometer (406) derived first feedback signal, a trailing electrode (E2) driven toward the same point by a second wire feeder (410) operated at a second speed by a second motor (M2) with a speed control input and a tachometer (416) derived second feedback signal, a first power source (292) directing a first current (I1) to flow through the leading electrode (EI) and a second power source (294) causing a second current (I1-I6) to flow through the trailing electrode (E2) with the current flow being in a series arc circuit. The second power source (294) is grounded to the workpiece (WP) to modify the series arc current so ground current (I6) flows to the workpiece (WP) whereby the second current is generally equal to the first current minus the ground current (I6).