Dc Welding Output - Lincoln Electric PRECISION TIG SVM186-A Service Manual

E-5 E-5
THEORY OF OPERATION

DC WELDING OUTPUT

When the polarity switch is placed in either DC position, the AC voltage from the main transformer secondary is
applied to the SCR bridge. The SCR bridge and choke circuits are connected in a conventional full wave bridge
and filter configuration, resulting in a controlled DC output. Since the choke is in series with the negative leg of
the bridge and also in series with the welding load, a filtered DC is applied to the machine output terminals.
CHOKE
ELECTRODE
G
G
DC
PRIMARY
1Ø
G
G
WORK
FIGURE E.5 DC Welding Current Generation.
PRECISION TIG® 225