ELECTRICAL SYSTEM
G e n e r a l l y, a f t e r r e a s s e m b l y, t h e g e n e r a t o r i s
MAINTENANCE
reinstalled in the unit it was taken from to seat the
brushes and perform operational tests.
LEARNING OBJECTIVE: Recognize
Typical testing procedures are as follows:
procedures for troubleshooting and
1. If you install new brushes, run the generator for
maintaining MEPP and MMGs.
20 to 30 minutes with no load to permit the
brushes to seat.
MEPPs and MMGs, like most complex support
2. Place an external load on the generator, not to
equipment, are inspected prior to each use and
exceed its rating.
periodically as required by the equipment manuals and
3. If operation is satisfactory, stop the engine and
the periodic maintenance requirements cards (MRCs).
replace the generator brush covers.
In some cases, local conditions may require more
frequent inspections than the MRCs. But, in no
4. Reposition the dc shunts.
instance should the interval between inspections
5. Replace all panels and door assemblies and
exceed the time specified on the MRCs.
secure them properly.
G e n e r a l l y s p e a k i n g , w h e n eve r t r o u b l e s o r
6. Adjust the generator to its rated output.
irregular operating characteristics are observed in this
equipment, you can trace it to improper maintenance
Testing procedures vary, and it is beyond the scope
and operation or to a malfunctioning component.
of this course to discuss all methods used for testing dc
Efficient maintenance of any system depends upon the
generators. You should consult the applicable manuals
skill and proficiency of the operating and maintenance
to determine the correct procedures for specific
personnel. This MEPP offers no exception to this rule.
generators.
The check, test, and repair of this unit require the
TROUBLESHOOTING
use of different kinds of test equipment and general
tools. Most technical manuals give a list of all special
A large portion of your time is spent
tools required for repairing the equipment.
troubleshooting or supervising the troubleshooting
NOTE: The troubleshooting and maintenance
procedures of others in maintaining assigned support
procedures addressed in this text are very general in
equipment.
nature, and may apply to any of the MEPPs discussed
Generator failures or apparent failures are due to a
in this course.
variety of causes. Before you remove a generator, take
the time to diagnose it properly. An apparent failure
TESTING
can be caused by a malfunctioning control or
Performance and calibration tests must be
regulating system. Troubleshooting charts similar to
completed on this unit to determine its ability to
table 7-4 are located in the manufacturers' manuals.
operate within prescribed limits under both no-load
They contain many probable causes and remedies for
and full-load conditions.
troubles found in dc generating systems.
The calibration tests for this MEPP require the
Procedures performed at the intermediate level
extensive use of test equipment. The use of this
include normal maintenance, replacement of brushes,
equipment and the procedures for calibrating such
diodes, and engine and generator control components.
u n i t s a s vo l t a g e r eg u l a t o r s , m e t e r s , p r o t e c t ive
Major repairs, such as rewinding armatures and field
packages, and checking harmonic distortions are
coils, are done at the depot maintenance activity.
beyond the scope of this NRTC. To perform calibration
"Troubleshooting" refers to the detection and
tests, or any other type of maintenance, always refer to
location of a malfunction by an orderly and systematic
the appropriate technical manual. This NRTC is not to
be used as a technical manual for any piece of support
procedure. To troubleshoot efficiently or supervise
equipment.
effectively, a minimum of the following information
must be known:
Operational testing of dc generators is required
What the system is supposed to do in normal
when a generator is replaced or repaired. This includes
operation and how to operate it.
brush replacement, disassembly, and reassembly.
7-48
