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GE Pegasus MHV GEEP-427-I Instuctions page 23

Horizontal induction motor totally enclosed water-to-air cooled sleeve bearing
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with extremely severe conditions. Good judgment and
common sense should be exercised when structuring the
maintenance program. Improper maintenance and
inspection can result in premature failure.
Stator Winding Inspection and
Maintenance
For special applications, such as belt drives, or on
smaller machines, a one piece solid end shield and
bearing may be supplied. Generally, direct-drive
machines are arranged to permit the removal of the upper
half of the end shield from either end for inspection
purposes without disturbing the motor line-up.
To gain access to the stator winding, first remove
the end shield upper half on each end of the unit. To
accomplish this, remove the screws which secure it to the
frame and to the bottom half of the end shield. Note that
a gasket is located between the mating surfaces for
sealing against moisture and dirt. This gasket should be
kept free of dirt for use during reassembly. On smaller
frame sizes, one or two men can lift the cover. On larger
frame sizes a hoist or crane is required.
Removal of the upper half of the end shield
exposes the top-half or a large opening in the end of the
frame. The air deflector or baffle can be seen inboard of
this semi-circular opening. Remove the top-half of the air
deflector on each end of the unit. To accomplish this,
remove the screws which secure it to the internal ring
and disconnect the L-clamps joining the upper and lower
air deflectors. If further accessibility is desired, rotate the
ring and lower the deflector. Remove the screws holding
the lower deflector to the ring. The lower air deflector
can now be removed.
deflector and end shield cover is the reverse of the
disassembly steps. This disassembly will provide access
to the entire top-half and some portion of the bottom-half
of the stator end turns, end turn bracing and ends of
stator wedges. For a routine inspection, this provides
sufficient view of the winding to indicate its general
condition and allows room for cleaning with a flexible
vacuum hose. When the rotor is removed on a less
frequent schedule, more of the winding is accessible.
GE Energy Motors GEEP-427-I
Note that reassembly of the air
GEEP-427-I Pegasus, Horizontal Induction Motor
For a routine inspection clean the accessible
portions of the winding with a vacuum hose equipped
with an appropriate non-metallic wand or nozzle. Refer
to the "Importance of Cleanliness" section of this
publication.. (Note that, if this is an emergency
inspection instead of a routine one, the first step is to
look for the fault, before disturbing the existing status of
the winding by cleaning.)
Inspect the stator coil bracing and support
structure. Look for evidence of looseness, movement or
chafing of the coil ends relative to the support structure.
Small "tails" and other similar surface irregularities of
the epoxy varnish on, and around, the surface geometry
of the coil bracing system is not significant and results
from the curing of the vacuum-pressure impregnation of
the prewound core. Check for tightness of the bracing
gussets to the core plate.
Inspect the stator coils end turns, connections and
wedge ends. All dirt or other foreign material
accumulations between coil sides should be removed
while exercising care not to damage the integrity of the
coil insulation. The surface of the coils should be free of
localized areas of damaged insulation resulting from
impact, such as would occur from being struck by an
edge of the rotor during a previous disassembly and
reassembly of the rotor assembly.
Because of the large volume of ambient air which
passes through ambient ventilated machines, certain
airborne, abrasive particles can wear away some of the
coil insulation over a period of time. Accordingly for
steel mill, coal mine, taconite and certain other
applications, considerable attention should be given to
observe this condition.
If cracks are evident in the varnish and are
associated with evidence of movement and chafing of the
bracing system, they should be investigated.
With the end shield cover and top air deflector
cover removed, access to the stator slot wedges is some
what limited. However, it is possible to obtain a
reasonable impression of wedge conditions from an
inspection of the ends. On a less frequently scheduled
basis, when the rotor is removed, the entire length of the
wedge may be viewed. The wedges should be tightly
secured. They should show no evidence of movement or
migration. The ends of the wedge should be free of
fraying. Again as indicated above for coil insulation,
Copyright 2009, The General Electric Company, USA 23
TEWAC, Sleeve Bearing

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