Dc Welding Output - Lincoln Electric SQUARE WAVE TIG 175 Service Manual

E-5 E-5
THEORY OF OPERATION

DC WELDING OUTPUT

When the polarity switch is placed in either DC posi-
tion, the AC voltage from the main transformer sec-
ondary 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 con-
trolled 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.
SQUARE WAVE TIG 175