TM 5-3431-207-15
64. Welding Current too Great or too Small
Compared to Indication of the Dial
Possible Remedy
See that current control indicator yellow
Probable cause
arrow in the horizontal position when
Current control, shaft and handle may have
handle is turned against stop in the
turned slightly in the insulated bushing of
minimum direction.
the current control brush holder, caused
by turning handle too hard against one of
Field discharge resistor wired to reversing
the stops.
switch and open-circuited.
Check for
Exciter output low causing low output
circuit through it.
compared to dial indication.
Motor is probably running backward or
series fields connector reversed to make a
Current control set to minimum and welder
cumulative series generate.
Check
output so great that motor stalls when arc
rotation.
is struck.
65. Motor Trips off the Line
Probable cause
Possible remedy
Power circuit may be single phased.
Check for a dead line.
Welder may be operating above current
Check load against welder nameplate.
capacity.
Welding electrode or work leads may be too
Check terminal voltage while machine is
long or too small in cross-section.
loading; it should not exceed 40 volts
Ambient temperature may be too high.
when operating at rated current.
Make sure that temperature in motor-
generator room or housing does not
exceed 100 degrees F., and that there is
not interference with normal ventilation of
the machine.
Motor input voltage too low (or high) under
Motor supply voltage should not fall below
load.
90% of normal voltage. Have power
company to check transformer and line
capacity. If supply loads too long or too
small they should be corrected.
66. Machine Fails to Start
Probable cause
Possible remedy
Power circuit may be single phased.
Check for a dead line.
Power-line voltage may not be suitable for
Check voltage with voltmeter, particularly at
motor, or may be extremely low; may be
the moment of attempted starting.
accompanied by chattering of the motor
starter.
Machine may be jammed.
See that armature turns over easily by hand
and look for foreign material in air gaps.
Motor starter may be single phased.
Check to see that all fingers on starter make
contact when closed.
Overload protecting device may be tripped
If machine has had time to cool after
or controls open-circuited.
tripping due to overload or is cold and
starter fails to close - check for circuit
through push button, NVR COIL and
thermostat to find
the open-circuited part.
See wiring
diagram for normally closed and open
contacts on the pushbutton.
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