
SEBU8088-06 105
Maintenance Section
Generator Load - Check
A small noncond
uctive tube may need to be
connected to the vacuum cleaner. This will allow the
vacuum cleaner to clean the surfaces that are not
exposed. Afte
r most of the dust has been removed,
a small brush may be attached to the vacuum hose
in order to loosen dirt that is more firmly attached to
the surface.
After the initial cleaning with a vacuum, compressed
air may be use
d to remove the remaining dust and
dirt. Compressed air that is used for cleaning should
be free of moisture and free of oil. Air pressure
should be a m
aximumof210kPa(30psi)inorderto
prevent mechanical damage to the insulation. If the
above cleaning procedures are not effective, consult
a Caterpill
ar dealer.
Cleaning (D
isassembled
Generators)
An initial insulation resistance check should be
made on the generator in order to confirm electrical
integrity
. A minimum reading of one megohm would
be expected with severely contaminated generators.
A zero megohm reading may indicate an insulation
breakdow
n. An insulation breakdown requires more
than cleaning. An insulation breakdown requires
repair.
Ahighpressurewashisnormallyaneffectiveway
to clean windings. This includes windings that have
been expo
sed to flooding or windings that have been
contaminated by salt. A solution of hot water and
detergent is used for this method of cleaning.
A high pressure wash sprays a high velocity fluid
stream of this solution over the generator that is
being cl
eaned. This detergent washing is followed by
multiple sprays of clean water. The clean water is
used in order to remove the detergent or the clean
water i
s used in order to dilute the detergent.
Allow the generator to dry at room temperature.
Check t
he insulation resistance. The insulation
resistance should now be normal. If the insulation
resistance is not normal, repeat the procedure. It
may be n
ecessary to use solvents if the generator
is contaminated with oil or if the generator is
contaminated with grease.
Note: For more information on drying methods, refer
to Special Instructions, SEHS9124, “Cleaning and
Dryin
g of Electric Set Generators”.
i01473721
Generator Load - Check
SMCS Code: 4450-535-LA
During normal o
peration, monitor the power factor
and monitor generator loading.
When a generat
or is installed or when a generator
is reconnected, ensure that the total current in any
one phase does not exceed the nameplate rating.
Each phase sho
uld carry the same load. This allows
the generator to work at the rated capacity. If one
phase current exceeds the nameplate amperage,
an electrica
l imbalance will occur. An electrical
imbalance can result in an electrical overload and an
electrical imbalance can result in overheating.
Thepowerfactorcanbereferredtoastheefficiency
of the load. This can be expressed as the ratio of kVA
to actual kW
. The power factor can be calculated by
dividing kW by kVA. Power factor is expressed as a
decimal. Power factor is used to mean the portion
of current
that is supplied to a system that is doing
useful work. The portion of the current that is not
doing useful work is absorbed in maintaining the
magnetic fi
eld in motors. This current (reactive load)
can be maintained without engine power .
Electric s
ets normally have a low idle setting that
is higher than industrial engines. Low idle will be
approximately 66 percent of the full speed that is
achieved
by 60 Hz units. This would be equal to 80
percent of the full speed that is achieved by 50 Hz
units.
Some electric sets are equipped with Woodward
governors and some electric sets are equipped
with Cat
erpillar electronic governors. These electric
sets have no low idle stop. On electric sets with
mechanical governors and natural gas electric sets,
the low i
dle is set at the factory. Adjustment of the
low idle on these machines should only be done by
a Caterpillar dealer.
Note: Operating the electric set at low idle speed for
an extended time will cause some voltage regulators
to shut
off. The electric set must be completely shut
down and the electric set must be restarted. This
will allow the voltage regulator to again produce an
output
.