Welding With Dc Constant Voltage (Cv; Mechanical Setup; Electrical Setup - Lincoln Electric NA-3 Service Manual

B-7
WELDING WITH DC
CONSTANT VOLTAGE (CV)

MECHANICAL SETUP

1. Set the head position relative to the
work as required for the fixture,
application, and procedures.
2. Rotate the wire straightener, if used,
until the top of the wire straightener
faces the wire reel. This is required
for smooth feeding of the electrode
into the straightener.
3. If using a K148 Contact Assembly,
rotate the assembly relative to
the direction of travel as shown in
Figure B.6.
4. The mount for standard 50 and 60 lb
(22.7 and 27.2 kg) electrode coils
includes
assembly. Generally the brake should
be at the inner position (nearest the
wire reel shaft) for wire speeds below
400 in./min (10.0 m/min). It should be
at the outer position for faster wire
speeds. To adjust the brake position,
the wire reel must be removed. Pull
the cotter pin that holds the brake
shoe to the arm; move the shoe and
replace the cotter pin. Do not bend
FIGURE B.6 – K148 CONTACT ASSEMBLY.
K148 CONTACT
ASSEMBLY
CONNECTOR
TAB
OPERATING INSTRUCTIONS
a two-position
CONTACT
PRESSURE
SPRING
NOZZLE
TRAVEL
WORK PIECE
TRAVEL
NA-3 AND NA-4
the cotter pin; it is held in place by a
friction fit.
5. Load the wire reel or install the speed
drum or reel.

ELECTRICAL SETUP

1. If using a multi-process power source
(SAM, SAF,
DC-1000, or DC-1500), set the power
source for constant voltage (CV)
welding per the instructions in each of
the power source manuals.
2. Set the wire feeder for constant
voltage (CV) welding.
3. Set the power source for the
electrode polarity [DC(+) or DC(-)]
specified
Interchange the NA-3 voltmeter and
ammeter leads if the polarity was
changed. If using the discontinued
brake
solid state remote field control with a
motor-generator power source, be
sure to set the power source and field
control to the same polarity before
starting the power source. Opposite
polarity settings will blow the fuse in
the field control.
4. Depending on the procedures and
applications, the following must be
decided:
a. Whether to use "hot" or "cold"
starting. Cold starting requires
the use of a constant voltage
board and cannot be used when
connected to an R3S power
source.
b. Whether to start the travel with
the "Start" button or the arc.
c. If control of the initial bead size
or penetration requires use of the
optional start controls PC board.
See Starting
Sequences later in this chapter for
descriptions of the various starting
sequences and the rewiring needed
to accomplish them.
5. Depending on the procedures and
applications:
a. Select the arc and travel stopping
sequence.
B-7
SA-800, DC-600,
by the procedures.
and Stopping