Table 7-4.--DC Generator Troubleshooting Chart--Continued
Probable Cause
Remedy
Armature Overheats--Continued
Armature coil shorted
Repair or replace armature.
Armature rubbing or striking poles
Check for bent shaft, loose or worn bearings.
Straighten and realign shaft. Replace bearings,
tighten pole pieces, or replace armature.
Clogged air passages (poor ventilation)
Clean equipment.
Repeated changes in load of great magnitude.
Generator should be used with a steady load
(Improper design for the application)
application.
Unequal brush tension
Equalize brush tension.
Broken shunts or pigtails
Replace brushes.
Open in field rheostat
Repair or replace rheostat.
Field Coils Overheat
Shorted or grounded coils
Repair or replace.
Clogged air passages (poor ventilation)
Clean equipment.
Overload (compound generator)
Check meter reading against nameplate rating.
Reduce load.
Sparking at Brushes
Overload
Check meter readings against nameplate ratings.
Reduce load.
Brushes off neutral plane
Adjust brush rigging.
Dirty brushes and commutator
Clean brushes and commutator.
High mica
Undercut mica.
Rough or eccentric commutator
Resurface commutator.
Open circuit in the armature
Repair or replace armature.
Grounded, open- or short-circuited field winding
Repair or replace defective coil or coils.
Insufficient brush pressure
Adjust or replace tension springs.
Brushes sticking in the holders
Clean holders. Sand brushes.
What each part or piece of equipment in the
conjunction with the applicable technical repair
manuals and electrical wiring diagrams aid greatly in
system contributes and how each functions.
correcting system malfunctions.
The location of all system components.
GENERAL REPAIRS
The most likely cause of any given malfunction.
The best places to "get into" the system for
In r e p a i r i n g M E P P s u p p o r t e q u i p m e n t , n o
making tests. This information is available in the
components or equipments should be rejected until
appropriate technical manuals.
every effort has been made to effect repairs or correct
the malfunction at the lowest maintenance level. As the
The appropriate maintenance instruction manuals
mechanic, you will be the most instrumental person in
provide troubleshooting procedures that include the
making such decisions. Your decisions should be
malfunction, probable cause, and the repair step.
influenced by the availability of personnel, availability
Troubleshooting tables, such as table 7-4, used in
7-50
