AUTOMATIC SHUTDOWN
If the NA-5 voltage control is unable to
supply the “Set” value of the arc voltage
while welding, the automatic shutdown
circuit will activate. This protection circuit
immediately returns the NA-5 control to idle
state within a few seconds after the arc
voltage discrepancy occurs.
Typical causes that activate this protective
shutdown circuit are as follows:
1. “Set” value of arc voltage is outside
the power source range.
2. Power source voltage control not set
for “Remote”.
3. Misconnection of NA-5 control cable
leads to the power source.
4. Incorrect weld polarity connections, or
settings, at NA-5 or power source.
5. Lost connection of NA-5 voltage
sensing leads (#67 and #21) between
arc and voltage control or a blown 1/8
amp fuse on voltage PC boards built
since 1983.
With NA-5 units above Code 8300, the
conditions of causes 4 and 5 above would
result in the wrong wire feed direction when
the weld is started. See the section on
Cold
Start Circuitry.
In the case of full-range control power
sources, such as the DC-600, this protective
shutdown circuit could prevent welding
under the conditions of causes 3, 4 and 5
above by holding the power output at
minimum, possibly providing too low of a
power source output to even establish an
arc, or causing the field fuse to blow
because of rapid field reversals with NA-5
controls above Code 8300. See the section
on
Cold Start Circuitry.
Although out of range shutdown can occur
with all power sources when working with
very low or very high arc voltages, it is most
likely to occur when using the R3S models
with the somewhat limited voltage ranges of
the various taps. For instance, if the R3S-
400 triangle tap setting is for 31 volts, the
range of control from the remote circuit is
approximately 7 volts, i.e. 27.5 to 34.5 volts
at nominal input voltage. If the NA-5
controls are set for 29 volts, and the input
voltage to the R3S goes up, it may not be
possible for the NA-5 control circuit to hold
the 29 volts, so the welding will shut down.
By changing to the 27 volt triangle setting,
the range will be approximately 23.5 to 30.5
volts, and at high input voltage, there will be
sufficient control to hold the “Set” arc
voltage. On these machines, if the NA-5
stops welding, follow this procedure:
1. Move the NA-5 voltage set point 2
volts lower than the desired
procedure and make a test weld.
a. If the NA-5 still shuts down, go to
step 2 below.
b. If the NA-5 keeps welding,
change the R3S triangle setting
to the next
higher voltage and
reset the NA-5 set point to the
desired procedure. The R3S is
now set properly unless there is
a significant change in input
voltage. Skip the following step.
2. Move the NA-5 voltage setting set
point 2 volts higher than the desired
procedure and make a test weld.
a. If the NA-5 keeps welding,
change the R3S triangle setting
to the next lower voltage and
reset the NA-5 set point to the
desired procedure. The R3S is
now set properly unless there is
a significant change in input
voltage. Skip the following step.
b. If the NA-5 still shuts down, refer
to the following paragraph and
other causes previously listed.
OPERATING INSTRUCTIONS
B-10
B-10
NA-5
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