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The
exact
amount
of desired
welding
current
within
the
range chosen
can
be selected
by rotating
the Fine
Current
Control
on
the front of the
welding
power
source.
The Cur
rent
Indicator
on
the front
panel
will show the
current
selec
ted.
When
reading
the Current Indicator for the amperage
selected,
ensure
that the scale
being
read
coincides with the
amperage range
being
used.
4-3.
ON-OFF
POWER SWITCH
The POWER
Switch controls
the
primary
line power
to
the
welding
transformer. When
the switch is
placed
in the ON
position,
open
circuit
voltage
will be
impressed
across
the
Work
and
Electrode
Receptacles
and
the
welding
power
source
will be in
a
ready-to-weld
status.
4-4.
DUTY CYCLE
The
duty cycle
of the
welding
power
source
is the
percentage
of
a
ten
minute
period
that
a
welding
power
source
can
safely
be
operated
at
a
given
output
current
setting.
This
welding
power
source
is rated
at
250
amperes,
30 percent
duty cycle.
This
means
the
welding
power
source
can
be
safely operated
at
250
amperes
welding
current
for three minutes
Out
of
every
ten.
If the
welding
current
is
decreased,
the
duty cycle
will increase.
Figure
4-2 enables the operator
to
determine
the safe
output
of the
welding
power
source
at
various
duty
cycles.
IMPORTANT
Exceeding
the indicated
duty cycle
will
cause
the
ma
chine
to
overheat and
thereby
cause
damage
to
the
~
machine.
35C
30C
25C
~20C
~
~
-
-
~
-
,.
.
~-..
1.
Make
primary
and
secondary
connections
as
outlined
in
Section 3.
4-5.
VOLT-AMPERE CURVE
The
volt-ampere
curve
shows the output
voltage
available
at
any
given
output
current
within the limits of the
minimum
and maximum Fine Current Contro!
setting.
Load
voltage
is
predetermined
to
a
large degree by
arc
characteristics. With
the
use
of
the
volt-ampere
curve,
it is
possible
to
determine
the amperage
required
for
a
specific
load
voltage.
With refer
ence
to
the
volt-ampere
curve
(Figure
4-3).
the
curve
shows
the maximum and
minimum
settings
of the Fine Current
Control
only.
Curves of other
settings
will fall between the
maximum and minimum
curves
shown.
3.
Rotate,
the
Fine
Current
Control
until
the
desired
amperage is indicated
on
the Current Indicator.
4.
Connect the work
clamp
to
the item
to
be welded.
5.
Place the desired electrode rod into the
electrode
holder.
6.
Put
on
protective
clothing
and
welding glasses.
7.
Place the POWER Switch
in the
ON
position
and
com
mence
welding.
8.
The Fine Current
Control
may
be
adjusted
while
welding
if necessary.
9. After the
welding job
is
completed,
break the
arc
and
place
the POWER Switch in the OFF
position.
SECTION
6-
MAINTENANCE
CAUTION
the branch circuit
or
main disconnect switch is
open
or
primary input
circuit fuses
are
removed before
attempting
any
inspection
or
work
on
the inside of the
welding
power
source.
Placing
the
ON-OFF POWER
Switch
on
the
welding
power
source
in the OFF
posi
tion
does
not
remove
voltage
from
the power
ter
minals inside of the machine.
6-1.
POWER FACTOR CORRECTION CAPACITORS
The power factor correction
capacitors
are
built into the
welding
power
source
as
standard
equipment
on
models with
power factor correction
only.
These
capacitors
should
require
no
maintenance
or
attention and should possess
an
infinite
life,
unless the power line is
subjected
to
high voltage
surges.
If
a
capacitor
should
fail,
it
can
readily
be
recognized
by
a
bulged
case
and oil
spillage
and
can
be
easily replaced.
RATED
OUTPUT
80
70
60
50
0
>40
4
30
20
10
0
50
100
150
200
250
300
350
400 450
A C AMPERES
B-002 206
80
70
60
In
50
0
>
40
~
30
20
10
0
50
100
150
200
250
300
350
400
450
DC
AMPERES
B-002
205
0
z
0
5-1.
SHIELDED METAL-ARC WELDING
(SMAW)
25
30
3~
40
50
60
70
80
90
100
%
DUTY
CYCLE
B-002 120-A
Figure
4-2.
Duty Cycle
Chart
Figure
4-3.
Volt-Ampere
Curves
SECTION
5
-
SEQUENCE
OF OPERATION
NOTE
An electrode holder and work
clamp
will have
to
be
supplied by
the
operator
and connected
to
the
welding
power
source
secondary
leads.
2.
Place the RANGE SELECTOR Switch in
the
desired
posi
tion.
Page
8
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