Removal And Replacement Of Components And Component Assemblies (Fb Dc, Ib Dc); Replacing The Bearings; Removal Of The Main Rotor; Removal Of The Rectifier Diodes - Sincro DC Serie Manual De Uso Y Mantenimiento

7.2 Removal and replacement of components
and component assemblies. FB-DC and
IB-DC.
The screws tightening torques for all reassembling
procedures are reported in the table of paragraph 6.2.4.

7.2.1 Replacing the bearings

Removal of the NDE bearing
• Unscrew the 4 nuts that fasten the back shield to
the housing.
• Disconnect the black and red wires from the AVR board.
• Hammer the shield evenly until it comes away from
the rotor.
• Remove the snap ring.
• Remove the bearing using a standard extractor.
• Take the new bearing and heat it so its diameter dilates
before sliding it into position on the shaft.
• Replace the snap ring.
• Position the shield remembering to insert the snap ring
and fit the screws leaving them loose.
• Hammer the shield evenly until the bearing and section
of housing are in place.
• Tighten the nuts on the shield.
Reassembly of bearings
Reassembly of the bearing should be made in reverse order
of the operation described above taking in the account the
following cautions:
• Before fitting the bearing, ensure that the coupling
surfaces both on the bearing and shaft has no signs of
wear;
• Heat the bearing to approximately 80° C before fitting
In case of regreasable bearing, follow the
procedure as described above, taking into
account to place back additional mechanical
parts used for bearing lubrication in the same
IMPORTANT!
position like they were prior to dismounting.
Apply the quantity and type of grease as
indicated on the generator nameplate.
it onto the shaft.

7.2.2 Removal of the main rotor

• Turn the rotor in position that the poles centerline is in
vertical position;
• Dismount the shields (NDE and DE) from the generators
as previously described;
• Using appropriately sized belt, support the DE side with it
and carefully start with tracking the rotor out of the stator.
As rotor come out of the stator, change the position of the
belt till the moment when it's approximately on the gravity
center of the rotor. During this process, it's necessary
to support the NDE end of the rotor to guide the rotor
precisely out of the stator to avoid any damages of the
stator or the rotor winding.
Reassembly
Reassembly of the rotor should be made in reverse order
of the operation described above taking in the account the
following cautions:
• in case that the any part of the rotor is changed, the
complete rotor must be re-balanced;
• in case of single bearing alternators, check if the coupling
discs are damaged.
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7.2.3 Replacing the rotating diode bridge
• Remove the shield NDE, as 7.2.1
• The replacement of the diode bridge can also be made
without disassembling the NDE bearing, dismantling the
bearing however makes the operation easier.
• Remove the 3-way connector and the two fast-on.
• Loosen the lock screw and remove the diode bridge
To replace the diode bridge, proceed backwards:
• Fix the bridge with the locking screw and thread lock
• Restore the original links, respecting the polarity
• Replace the bearing shield and protective grid
7.2.4 Replacing the fan
• Uncouple the alternator from the drive motor
• Remove the shield DE side (in the case of mounting
IMB34)
• The fan is locked on the shaft through a key (1). Loose
the screw (2), without removing it, and then hit the screw
head with a hammer. This will allow the tongue to move
inside the angle seat, freeing the fan.
• Before removing the fan, mark the location of the washers
(mounted on the fan itself) used for balancing
• Then remove the screw and remove the fan
To replace the fan proceed backwards:
• Place the shaft key (1) in the key seat
• Insert the fan (by hand, or with the help of a rubber
hammer)
• Insert the screw (2), screw it into the tab (with thread
lock) and tighten it following the torque values shown in
paragraph 6.2.4
• Replace the balancing washers in their original position
(make sure that they are locked)
7.2.5 Changing rotor exciter
• Remove the shield NDE, as 7.2.1
• Remove the bearing NDE
• Disconnect and remove the rotating diode bridge (see
7.2.3)
• The exciter rotor is locked to the shaft through a key (1).
Loose the lock screw (2), without removing it, and then hit
the screw head with a hammer. This will allow the key to
move inside the key seat, in order to free the exciter rotor.
• Remove the screw and remove the exciter rotor.
To replace the exciter rotor work backwards:
• Place the key (1) in its seat
• Insert the cables of the main rotor in the exciter rotor
• Insert the exciter rotor (by hand, or with the help of a
rubber hammer)
• Insert the screw (2), screw it into the tab (with thread
lock) and tighten it following the torque values shown in
paragraph 6.2.4
• Reconnect the diode bridge observing the polarities
• Replace the bearing shield and protective grid.