CAUTION:
WINDING
VARNISHES
ARE
EPOXY
OR
POLYESTER
BASED
MATERIALS.
A
SOLVENT
THAT
DOES
NOT
ATIACK
THESE
MATERIALS
SHOULD
BE
USED.
Apply
the
solvent with a soft brush
or
rag.
Be
careful not to damage the magnet wire
or
insulation
on
the windings. Dry components thoroughly with moisture-free, low pressure compressed air.
WARNING
ADEQUATE
VENTILATION
MUST
BE
AVAILABLE
TO
A
VOID
FIRE,
EXPLOSION,
AND
HEALTH
HAZARDS
WHERE
SOLVENTS
ARE
BEING
USED.
AVOID
BREATHING
SOLVENT
VAPORS.
RUBBER
GLOVES
AND APRONS,
OR
OTHER
SUITABLE
HAND
AND
BODY
PROTECTION
SHOULD
BE
USED ..
WEAR
EYE
PROTECTION.
Cloth
and
Compressed
Air.
Cleaning with a dry cloth may be satisfactory when components are
small, the surfaces are accessible, and only
dry dirt
is
to be removed. Blowing dirt
out
with
compressed air is usually effective particularly when the dirt
bas
collected in places that cannot be
reached with a cloth.
Use clean dry air
at
30
PSI
(206 KP A).
Brushing
and
Vacuum Cleaning.
Dry
dust and dirt
may
be removed by brushing with bristle
brushes followed by vacuum cleaning.
Do
not use wire brushes. Vacuum cleaning is an effective and
desirable method
of
removing dry and loose dirt.
Steam
Cleaning.
If
the generator is completely disassembled, including bearings and rotating
rectifier assembly, steam cleaning
of
major parts and windings
is
very effective. However,
the
machine must be thoroughly dried in an oven
to
remove all moisture before the unit
can
be
put back
into service.
Restoring
Residual Magnetism. The current necessary to magnetize the alternator field during
operation
is
obtained from the exciter. Initially, upon starting the unit, voltage is induced into the
main
stator (armature) by the flux across the air gap supplied by the permanent magnets embedded in
the poles
of
the main rotor. Current then flows through interconnecting leads
to
the shunt portion
of
the
exciter stator which induces current in the exciter rotor. This current is then rectified
to
DC
excitation current by the rotating rectifier, and fed to the
main
field windings via
the
main
rotor leads
further strengthening the main field until rated voltage
is
reached.
The residual magnetism contained in
the
field poles
of
the
main
rotor
may be lost
of
severely
weakened by a strong neutralizing magnetic field from any source,
or
if
the unit has
not
operated for
a long period
of
time. Should
the
generator
.fail
to build up voltage after being disassembled for any
reason, a momentary short circuit
of
any
two
generator output leads should be sufficient
to
correct
this condition.
If
not, an alternate method may be used. Apply either an alternating
or
direct current
voltage
of
from 20 to 30 volts
to
any
two
generator output leads.
Do
not make a
firm
connection, but
rather tough the leads together until
the
generator voltage begins
to
rise and then remove.
It
is
suggested that a
30 ampere· fuse be inserted in the supply voltage circuit
to
prevent any damage in
case the build-up power supply voltage is not removed quickly enough.
Both
of
these procedures
must be conducted while the generator is running at rated
1800
RPM
or
slightly higher speed.
11
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