CHAPTER 7
MAINTENANCE AND REPAIR
OF ROTATING ELECTRICAL
MACHINERY
ventilation ducts and increase resistance to the
The main objective of shipboard preventive
maintenance is the preventing the breakdown,
dissipation of heat, causing local or general overheating.
deterioration or the malfunction of equipment. If this
If the particles form a conducting paste through the
objective is not met, failed equipment must be repaired
absorption of moisture or oil, the motor or generator
or replaced. By performing preventive maintenance
windings may eventually be short-circuited or
according to the prescribed procedures, you can ensure
grounded.
proper operation of the equipment in the ship's electric
Additionally, abrasive particles may puncture
plant. However, despite your best efforts, on occasion
corrective action will be required to restore the electric
insulation; iron dust is particularly harmful since the
plant to peak operating conditions. This chapter
dust is agitated by magnetic pulsations. The acceptable
describes maintenance practices and procedures for
methods of cleaning motors and generators involve the
preventing casualties to, and for diagnosing, repairing,
use of wiping rags or cloths, suction, low-pressure air,
and testing shipboard electric motors and generators.
and solvents. Wiping with a clean, lint-free, dry rag
For additional information, refer to Naval Ships'
(such as cheesecloth) is effective for removing loose
TechnicalManual (NSTM), chapters 300, 302, and 310,
dust or foreign particles from accessible parts of a
and Naval Sea Systems Command Technical Manual,
machine. When wiping, do not neglect the end
0900-LP-060-2010, "Electric Motor Repair."
windings, mica cone extensions at the commutator of dc
machines, slip-ring insulation, connecting leads, and
LEARNING OBJECTIVES
terminals.
Upon completion of this chapter, you will be able to
The use of suction is preferred to the use of
do the following:
compressed air for removing abrasive dust and particles
1. Identify the procedures to be followed in
from inaccessible parts of a machine because it lessens
cleaning motors and generators.
the possibility of damage to insulation. If a vacuum
2. Identify various types of bearings and their
cleaner is not available for this purpose, a flexible tube
proper care.
attached to the suction side of a portable blower will
3. Describe the procedures for maintaining and
make a suitable vacuum cleaner. Always exhaust the
overhauling commutators and collector rings.
blower to a suitable sump or overboard. Whenever
4. Describe the steps to be followed in overhauling
possible, remove grit, iron dust, and copper particles by
and rewinding dc machines and armatures.
suction methods.
5. Describe the methods of overhauling and
Clean, dry, compressed air is effective in removing
rewinding ac machines.
dry, loose dust and foreign particles, particularly from
6. Describe the operation of motor and generator
inaccessible locations such as air vents in the armature.
air coolers.
Air pressure up to 30 pounds per square inch (psi) may
be used to blow out motors or generators. Where air
lines carry higher pressure than is suitable for blowing
CLEANING ROTATING
ELECTRICAL MACHINERY
out a machine, use a throttling valve to reduce the
pressure. Always blow out any accumulation of water
One of your most important jobs is to keep all
in the airlines before directing the airstream on the part
electrical machinery clean. Dust, dirt, and foreign
or machine to be cleaned.
matter (such as carbon, copper, and mica) tend to block
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