3. Periodically inspect the unit for buildup
of
contamination (dirt, oil, etc.) on the windings. Clean
as necessary following instructions in the Service Section
of
this manual.
SERVICE
Drying
Generator
Windings. Generators that have been in transit
or
storage for long periods
of
time may be subjected
to
extreme temperature and moisture changes. This can cause excessive
condensation, and the generator windings should be thoroughly dried .Jut before operating the unit.
If
this precaution is
not
taken, serious damage
to
the generator can result.
CAUTION:
DO
NOT
RUN
THE
GENERATOR
AT
RATED
SPEED
WITH
WET
OR
VERY
MOIST
WINDINGS.
THE
EXCITATION
SYSTEM
IS
SUCH
AS
TO
CAUSE
VOLTAGE
TO
BE
PRESENT
\VHENEVER
THE
UNIT'S
SHAFT
IS
ROTATING
ABOVE
1200
RPM.
The following procedures should be taken to effectively dry the unit's windings:
Oven. Place the machine in an oven and bake it at a temperature not
to
exceed 194° F (90° C).
Hot
air.
Run
the engine at a low idle speed, not
to
exceed 1000 RPM, and blow hot air from a space
heater
or
other appropriate device into the generator's intake air openings. Suggest this be done for at
least one hour.
To
prevent harmful voltages being generated in the stator windings during the dry-out
period, it is necessary
to
keep shaft speed below the generator's voltage build-up speed.
For
this
procedure, bring the engine speed as slowly as possible up to 1000 RPM, Do
not
let
the
engine
speed exceed 1000
RPM
during
start-op
or
during
the
drying
process.
Cleaning
Methods.
When electrical components get dirty, the insulation must be cleaned. There are a number
of
acceptable methods for cleaning the generator, each
of
which will necessitate disassembly
of
the unit.
The method
of
cleaning will be determined by
the
kind
of
dirt,
and when the unit must be placed into
service. Drying after cleaning
is
necessary. An authorized Marathon Service Center,
or
an electric
motor repair shop in your area can normally assist with the proper cleaning
of
the generator
windings. They will usually be experienced in problems areas such as road salt, dust,
dirt, engine oil,
and
coastal marine environments.
Whenever the generator is disassembled, the windings should be given a thorough inspection, and the
insulation cleaned,
if
necessary. The inspection should include the connection
of
the
windings,
insulation, and varnish coverage. Check the winding ties and coil supports.
Look
for any sign
of
coil
movement
or
looseness, and repair as required.
Solvents. A solvent is usually required
to
remove accumulated soil containing oil
or
grease. Only
petroleum distillates should be used for cleaning electrical components. Petroleum solvents
of
the
safety type with a flash point
of
greater than 100° F (38° C) are recommended.
10
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