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in atmospheres that are much more corrosive than
others. A little precaution along the lines outlined here
could eliminate an unnecessary repair job.
Each generator was subjected to a standard NEMA
insulation test, which means 1000 volts plus twice the
highest voltage for which the generator is rated was
impressed between the winding and frame. All machines
are insulated with a high safety factor for the class of
insulation used. The latest and newest in insulation and
baking techniques are used.
The finest insulation job can be very quickly broken
down by carelessly applying high voltage to windings in a
moisture saturated condition. Mishandling in this respect
can easily cause a breakdown, making it necessary to
return the generator to the factory for repair, and
consequent expense and loss of time.
g. Restoring Residual Magnetism
NOTE
When trying to restore residual magnetism, be
sure to wear leather gloves and use an insulated
12 gauge (or higher) jumper wire. Cut-off a few
strands from both ends of the jumper wire to
help ensure fusing does not take place.
The direct current (DC) necessary to magnetize the
alternator field is obtained from the exciter. Initially,
upon starting the generator, current flow and voltage are
induced into the exciter armature by the magnetic lines of
force set up by the residual magnetism of the exciter field
poles.
Residual magnetism of the exciter field poles may be
lost or weakened by a strong neutralizing magnetic field
from any source, or if the generator is 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 leads (L1, L2 and L3)
while generator is running should be sufficient to correct
this condition. If not, an alternate method may be used.
Apply either an alternating current or a direct current
voltage of approximately 20 volts to any two generator
leads (L1, L2 and L3) while generator is running. Do not
make a positive connection but rather touch 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 circuit to prevent any damage in case the
build-up voltage is not removed quickly enough.
Reflash field if generator output voltage does not
build up.
4.5.2 Installation and Removal
a. Removing the Generator
1. Remove ground wire from frame of generator set.
2. Remove generator leads from power junction box,
then remove four 1/4-20 x 1/2 thread cutting screws
securing box to generator.
3. Remove screen from coupling end of generator.
4. Remove twelve M10 x 1.5 x 25mm lg socket head
bolts and washers securing the generator flange to the
engine flywheel housing. Turn bolts counter-clockwise
with offset wrench to start, then use flexible shaft and
socket assembly for removal of bolts.
5. Remove eight M10 x 1.5 x 25mm lg socket head
bolts and washers that secure generator to engine
flywheel.
6. Remove mounting frame hardware (four --- 5/8-11
x 2-1/2 lg hex head bolts and washers), then remove
generator.
b. Installing the Generator
The generator is a single bearing type which means
the shaft end of the rotor floats. Before installing
generator, rotate shaft and check if bearing rotates.
1. Remove screen covering from shaft end of
generator and brush anti-seize lubricant (lube-plate) on
the face of flywheel.
2. Move generator (with hoist) into position and line
up with the holes on housing and flywheel. Turn
crankshaft (with large wrench) to align flywheel with
generator, if necessary.
3. Start the M10 bolts (by hand) through the disc
plate and into the flywheel. Once alignment is made
torque bolts (eight) to a value of 20 ft-lb (2.77 mkg).
4. Secure two of the housing bolts (M10) to draw the
mating flanges together.
5. Secure remaining bolts and washers. The M10
bolts (twelve) are to be torqued to a value of 20 ft-lb (2.77
mkg).
6. Install screen cover, mounting bolts, power
junction box, generator leads and ground wiring. Torque
generator mounting frame bolts (5/8-11) to a value of 97
ft-lb (13.41 mkg).
Install new gaskets (one between generator and
junction box and the other between box and
cover) when installing junction box.
4.6 MAINTENANCE OF PAINTED
SURFACES
The unit is protected by a special paint system against
the corrosive atmosphere in which it normally operates.
However, should the paint system be damaged, the base
metal can corrode. In order to protect the unit from the
highly corrosive sea atmosphere or if the protective paint
system is scratched or damaged:
a. Clean area to bare metal using a wire brush, emery
paper or equivalent cleaning method.
b. Immediately following cleaning, spray or brush on
a zinc rich primer.
c. After the primer has dried, spray or brush on finish
coat of paint to match original unit color.
4-6
NOTE
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