recommended practice to record the no load excitation
(DC voltage to the exciter stator), generator terminal
voltage, and driver speed as a benchmark for future
troubleshooting.
8. Close the main circuit breaker to the load.
9. Monitor the generator output current to verify that it is at
or below nameplate value.
10. Check generator speed (frequency) under load. Adjust as
necessary. (Refer to prime mover or governor manuals)
SHUTDOWN PROCEDURE
There are no specific instructions for shutting down the
generator; however, several good practices should be
observed to prolong equipment life.
1. It is advisable to disconnect all loads (open main circuit
breaker or disconnect) prior to shutdown. This is
especially important if loads can be damaged by low
voltage or low frequency conditions during generator
"coast down".
2. Isolate all conditions that could apply voltage to the
generator terminals while the generator is at rest. Failure
to comply could result in personnel injury or equipment
damage.
3. If the unit is equipped with space heaters, verify that the
heater circuit is energized.
MAINTENANCE
The following maintenance procedures should be followed to
ensure long equipment life and satisfactory performance.
Maintenance intervals will depend upon operating conditions.
1. Routinely check intake and exhaust air screens to ensure
that they are clean and free of debris. Clogged intake air
screens will reduce cooling air flow and result in higher
operating temperatures. This will reduce generator life
and may result in generator damage.
2. All MagnaPLUS
®
generators are equipped with double
shielded ball bearings lubricated for the life of the
bearing. Every 1,000 hours check the bearing(s) for
smooth, quiet operation. For continuous duty generators,
recommended practice is to replace the bearing during
major overhauls of the engine.
3. Periodically inspect the unit for any buildup of
contamination (dirt, oil, etc.) on the windings. If the
wound components have become coated with heavy
concentrations of oil and grime, the unit should be
disassembled and thoroughly cleaned. This operation is
not one that can be accomplished effectively on site, but
rather one that should be conducted by an authorized
service center equipped with the appropriate apparatus
and solvents necessary to properly clean and dry the
generator.
THE FOLLOWING TEST MUST BE CONDUCTED BY
QUALIFIED ELECTRICAL PERSONNEL. LETHAL
VOLTAGE MAY BE PRESENT AT BOTH THE
GENERATOR AND VOLTAGE REGULATOR
TERMINALS DURING THIS PROCEDURE. CAUTION
MUST BE EXERCISED NOT TO COME INTO
PERSONAL CONTACT WITH LIVE TERMINALS,
LINKS, OR STUDS. SERIOUS INJURY OR DEATH
COULD RESULT.
4. Every 2,000 operating hours or in conjunction with
scheduled engine maintenance, check the DC no load
excitation voltage per item #7 in the startup procedure.
Compare this voltage with the value recorded during
initial startup. If this value of no load excitation voltage is
markedly higher than the bench mark reading, it is an
indication of problems in either the exciter, main field, or
the rotating rectifier assembly. Ensure that RPM is the
same as initial test.
5. Monitor and record insulation resistance with a 500 volt
mega-ohm meter. The minimum acceptable reading is 2
mega-ohms. If the reading drops below the minimum, the
generator should be cleaned and dried at an authorized
service shop. Consult Marathon Electric for more
information.
DRYING WINDINGS
Generators in service may inadvertently have their windings
exposed to splashing or sprayed water. Units that have been
in transit or storage for long periods of time may be
subjected to extreme temperature and moisture changes
causing excessive condensation. Regardless of the source of
moisture, wet windings should be thoroughly dried out before
operating the unit. If this precaution is not taken,
serious damage to the generator can result. The following
procedures may be utilized in drying the generator’s
windings. The method selected will be influenced by winding
wetness and situation limitations.
Space Heaters
An electric heater may have been supplied with the
generator. When energized from a power source other than
the generator, the heater will gradually dry the generator. This
process can be accelerated by enclosing the unit with a
covering and inserting additional heating units. A hole should
be left at the top of the covering to permit the escape of
moisture. Care should be taken not to overheat various
accessory equipment mounted with the generator.
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