Page 49
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Symptom Cause Remedy
Low voltage
(cont.)
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 fi eld Test the fi eld coils for possible short by
checking resistance with an ohmmeter or
resistance bridge. Return the rotor assembly
to the factory for repair if fi eld 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 larger horsepower rating than
is necessary to carry the mechanical
load.
Weak fi eld 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 nameplate is not
exceeded.
Defective rectifi ers in rectifi er assembly
(stationary)
Check rectifi er assembly. Replace
defective fuses or rectifi ers.
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 defi ciencies.
Voltage regulator not operating properly Check the regulator. Adjust, repair or replace.
Fluctuating
voltage
Prime mover speed fl uctuating 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 fl uctuating Trace DC excitation circuit. Correct any
defects.
Overspeed 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.
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