
110 SEBU8219-01
Maintenance Section
Generator Load - Check
Cleaning (Disassembled
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
breakdown. An insulation breakdown requires more
than cleaning. An insulation breakdown requires
repair.
Ahighpressurewashisnormallyaneffectiveway
to clean windings. This includes windings that have
been exposed 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 cleaned. 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 is used in order to dilute the detergent.
Allow the generator to dry at room temperature.
Check the insulation resistance. The insula tion
resistance should now be normal. If the insulation
resistance is not normal, repeat the procedure. It
may be necessary 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
Drying of Electric Set Generators”.
i01473721
Genera
tor Loa d - Check
SMCS Code: 4450-535-LA
During normal operation, monitor the power factor
and monitor generator loading.
When a generator is installed or when a generator
is reconnected, ensure that the total current in any
one pha
se does not exceed the nameplate rating.
Each phase should carry the same load. This allows
the generator to work at the rated capacity. If one
phase
current exceeds the nameplate amperage,
an electrical imbalance will occur. An electrical
imbalance can result in an electrical overload and an
elect
rical imbalance can result in overheating.
The power facto
r can be referred to as the efficiency
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 field in motors. This current (reactive load)
canbemaint
ained without engine power.
Electric sets normally have a low idle setting that
is higher th
an 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 t
he full speed that is achieved by 50 Hz
units.
Some electr
ic sets are equipped with Woodward
governors and some electric sets are equipped
with Caterpillar electronic governors. These electric
sets have n
olowidlestop.Onelectricsetswith
mechanical governors and natural gas electric sets,
the low idle is set at the factory. Adjustment of the
low idle o
n these machines should only be done by
a Caterpillar dealer.
Note: Ope
rating 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 t
he electric set must be restarted. This
will allow the voltage regulator to again produce an
output.