ESAB Heliarc 250 Instruction Manual page 11

SECTION 3
L. Arc Force Potentiometer (AFP). This control is
used in the STICK mode only. The lower settings
provide less short circuit current and a softer, more
stable arc. The higher settings provide more short
circuit current and a forceful, more penetrating arc.
For most Stick welding, set the knob at 3 or 4 and
readjust up (forceful) or down (softer) as desired.
Note that with the knob in the MIN. position, a longer
arc length can be maintained; and at MAX., the arc will
extinguish much easier when drawing the rod away
from the work.
M. Balance Control Potentiometer (BP). This control
changes the wave balance for Tig welding operations
(see Fig. 3-1). It is not operative in Stick welding
operations. With the potentiometer set in its extreme
counterclockwise or "Max. Cleaning" position, the
machine is set up for "balanced" wave operation
(equal portions of reverse and straight polarity - 50/50)
for use in DC and AC Tig with Maximum Cleaning
(and minimum penetration). This will be the normal
(counterclockwise) position for most applications. As
the potentiometer is turned clockwise toward "Max.
Penetration", cleaning action will lessen and penetra-
tion will increase until you reach Maximum Penetra-
tion. This "unbalanced" wave output (straighter than
reverse polarity) should only be used for AC Tig
applications when needed.
Figure 3-1. Square Wave Operation
IMPORTANT: When using "Maximum Penetration" in
AC Tig; the duty cycle will be reduced
50% (25% with p.f) and input current will
increase approximately 40%. Also, when
DC Tig welding, the Balance Control
should always be set to the Maximum
Cleaning (balanced wave) position.
NOTE: Square wave machines generally offer better
cleaning in AC tig welding than conventional
saturable reactor machines. The extra cleaning
results from more reverse polarity which de-
creases the maximum current for a given elec-
trode. The following may help to resolve this
situation: (1) Adjust the balance control for less
cleaning, (2) use a larger electrode, and (3) use
2% thoriated tungsten.
3.2 Sequence of Operation
ELECTRIC SHOCK CAN KILL! Do not use AC output
in damp areas, if movement is confined, or if danger
of falling exists.
Use AC output only if required for the welding pro-
cess.
Never, under any circumstances, operate the power
source without its panels in place. In addition to the
safety hazard, improper cooling may cause overheat-
ing which will damage the internal components. Also,
make sure you are adequately protected before you
start welding -- welding helmet, gloves, and ear pro-
tection and safety glasses with side shields should
always be worn.
A. STICK ELECTRODE/SHIELDED METAL ARC
WELDING
1. Connect all welding cables to workpiece and elec-
trode holder as shown on the Interconnection Dia-
gram, Fig. 2-1.
2. Place the power source's Power ON-OFF and High
Frequency Selector switches to the OFF position.
3. Close the main (wall) disconnect switch or circuit
breaker to provide input voltage to the power source.
4. Place the Current Selector switch to AC, DCSP, or
DCRP depending on your welding application.
ELECTRIC SHOCK CAN KILL! Do not use AC output
in damp areas, if movement is confined, or if danger
of falling exists.
Use AC output only if required for the welding pro-
cess.
3-2
OPERATION
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