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predetermined manner, the operation of the dc or ac
such as cracks in the material and separation at the
motor to which it is connected. Preventive mainte-
seams. Ventilation opening located to permit water to
nance of motor controllers should be accomplished
discharge onto electrical equipment, insufficient
while consulting the applicable PMS card. Trouble-
insulation overhead to prevent sweating, need for
shooting and corrective maintenance of motor
dripproof covers and spray shields, and location of
controllers is discussed in depth in Interior
water piping and flanges where leakage could spray
Communications Electrician, volume 2, NAVEDTRA
onto switchboards and other gear are examples of
installations that could cause casualties. Action should
be initiated to have unsatisfactory conditions
Distribution Boxes
Wiring distribution boxes (fused), with and without
Now that we have discussed the different types of
switches, that feed vital circuits should be checked
power distribution systems and switchboards and the
annually. Tighten fuse clip barrel nuts and terminal
maintenance of switchboards, we will discuss the
connections. On anew ship and after a major overhaul,
maintenance and repair of two of the most common
tighten and prick punch loose bus bar nuts on the backs
power supplies: motor generators and static inverters.
of insulating bases.
The phosphor-bronze fuse clip and supplementary
bent-wire fuse retainer have been superseded by a steel
Under normal conditions, the motor generator set
copper-clad silver-plated fuse clip. The steel fuse clips
and control equipment require inspection and cleaning
do not require fuse retainers to prevent dislodgement
as designated by the PMS MRCs. When the motor
of fuses under shock and vibration. The wire fuse
generator is inspected, cleanliness, brush operation,
retainers impose a hazard of possible accidental
condition of brushes and commutator, bearing tempera-
dislodgement and falling into bus work to cause short
ture, and vibration should be observed.
circuits. To eliminate this hazard on both vital and
The acceptable methods of cleaning motors and
nonvital circuits that require frequent removal of
generators involve the use of wiping rags or cloths,
fuses, and where difficulties occur with loosening of
suction, low-pressure air, and solvents.
Wiping with a clean, lint-free, dry rag (such as
existing phosphor-bronze fuse clips and wire fuse
retainers, steel copper-clad silver-plated fuse clips
cheesecloth) is effective for removing loose dust or
should be used. Do not remove the wire retainers until
foreign particles from accessible parts of a machine.
the new steel fuse clips are on board for substitution.
When wiping, do not neglect the end windings, mica
Tighten the fuse-clip barrel nut until the arch in bottom
cone extensions at the commutator of dc machines,
of the steel fuse clip is drawn flat.
slip-ring insulation, connecting leads, and terminals.
The use of suction is preferred to the use of com-
Emergency Switchboards
pressed air for removing abrasive dust and particles
from inaccessible parts of a machine because it lessens
Emergency switchboards should be tested regu-
the possibility of damage to insulation. If a vacuum
larly, according to the instructions on the switchboard,
cleaner is not available for this purpose, a flexible tube
to check the operation of the ABT equipment and the
attached to the suction side of a portable blower will
automatic starting of the emergent y generator.
make a suitable vacuum cleaner. Always exhaust the
All other preventive maintenance should be
blower to a suitable sump or overboard. Whenever
performed according to the applicable PMS card.
possible, remove grit, iron dust, and copper particles by
Remember, when you are conducting tests or trouble-
suction methods.
shooting equipment, the first thing you should do is
Clean, dry, compressed air is effective in removing
consult your PMS schedule. By doing this, you will
dry, loose dust and foreign particles, particularly from
find information to assist you.
inaccessible locations such as air vents in the armature.
Use air pressure up to 30 pounds per square inch (psi)
to blow out motors or generators of 50 horsepower (hp)
or 50 kilowatts (kW) or less; use pressure up to 75 psi
to blowout higher-rated machines. Where airlines carry
By definition, a motor controller is a device (or
higher pressure than is suitable for blowing out a
set of devices) that serves to govern, in some

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