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Symptom
Cause
Remedy
Low voltage
Shorted leads between
the exciter armature and
generator field.
Test and repair.
Incorrect stator
connections.
Check the connections and reconnect.
Improper adjustment of
voltage adjust rheostat
Adjust rheostat.
Excessive load
Reduce load. With three-wire, single-phase and
four-wire, three-phase generators, the load on each
leg must be as evenly balanced as possible and must
not exceed the rated current on any leg.
Line loss.
Increase the size of the line wire.
High resistance
connections (hot).
Make better connections.
Shorted main or exciter
field.
Test the field coils for possible short by checking
resistance with an ohmmeter or resistance bridge.
Return the rotor assembly to the factor for repair if
field coils are shorted.
Low power factor.
Reduce inductive (motor) load. Some AC motors
draw approximately the same current regardless of
load. Do not use motors of large horsepower rating
than is necessary to carry the mechanical load.
Weak field due to
operating in a warm
temperature.
Improve the ventilation of the generator. Field
current can be increased providing the generator
temperature rating stamped on the name plate is
not exceeded.
Defective rectifiers
in rectifier assembly
(stationary).
Check rectifier assembly. Replace defective fuses or
rectifiers.
Excessive load.
Reduce load to rated value.
Defective bearing.
Replace the bearing.
Improper speed of engine
driven generator set due
to defective governor,
ignition system, or
carburetor.
Check and correct deficiencies.
Voltage regulator not
operating properly.
Check the regulator. Adjust, repair or replace.
Fluctuating
voltage
Prime mover speed
fluctuating.
Check frequency and voltage of incoming power
when the generator set is motor driven Check
engine governor on engine-driven generator sets.
Loose internal or load
connections.
Tighten all connections.
Generator overloaded.
Reduce load to rated value.
DC excitation voltage
fluctuating.
Trace DC excitation circuit. Correct any defects.
Over-speed.
Correct speed of prime mover.
Voltage regulator not
operating properly.
Check the regulator. Adjust, repair or replace.
High voltage
Improper adjustment of
voltage adjust rheostat or
voltage regulator.
Adjust rheostat and/or voltage regulator.
Voltage regulator not
operating properly.
Check the regulator. Adjust, repair or replace.
Overheating
Clogged ventilating
screens and air passages.
Clean all screen and air passages.
Dry or defective bearings.
Replace defective bearings.
Coupling misaligned.
Align the generator set.
Generator field coils
shorted or grounded.
Test field coils for shorts. Replace shorted rotor or
return it to the factory for repair.
Unbalanced load or
overload, low PF.
Adjust load to nameplate rating.
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