Reassembly Operations; Voltage Regulator - MarelliMotori M8B 315 Instructions And Safety Information

- remove the bolts fixing the N.D.E. shield to the frame and dismantle the shield
The rotor can be extracted from the stator, from D.E. side.
It should be remembered that the exciter stator is fixed to the N.D.E. endshield: special care should be taken to avoid any damage to its
windings when removing the N.D.E. shield; furthermore be sure the connections or the exciter stator are free to slide out from terminal
box.
If a bearing needs to be replaced, remove it with a suitable puller.
For M8B 500 generators:
Dismantling operations on N.D.E. side (on side opposite to shaft ext.).
-Remove the cover (45, 33) protecting the N.D.E. side
-Disconnect all the wiring from the rotating rectifier and then remove the rectifier (119)
-Disconnect the leads connecting the exciter stator to the terminal box (connection terminals are on exciter stator)
-Remove the exciter stator (110) after having removed the screws securing it to the endshield (5). Care should be taken in order
not to damage the winding of exciter rotor or stator during this operation
-Remove the screw (504) fixing the exciter rotor to the shaft
-Remove the exciter rotor (100) by using suitable puller (rods M12)
-Remove the screws fixing the internal bearing cap (142) of the N.D.E. bearing
-Remove capscrews holding the N.D.E. end-shield (5) to the main stator assembly
-Remove the N.D.E. shield (5). During this operation it is necessary to take care to sustain the main rotor in order it will not fall
heavily on the stator.
On the internal side of the bearing some preloading springs are placed on proper holes: it is necessary to collect them in order to
replace them in the proper position during reassembly of the generator.
-Remove the locating ring (305) fixing the rotating lubrication valve (143) to the shaft, and then remove the rotating valve (143)
-In case should be necessary to remove completely the N.D.E. bearing (202), it is necessary to use a proper puller, taking care that the
arms of the puller are pulling on the inner ring of the bearing; further care should be taken that the puller is not damaging the cables
coming out from the shaft hole (in case, insert a proper spacer between puller and shaft end, in order not to press those cables).
Dismantling operations on D.E. side
Remove the guard protecting the generator at the D.E. side (49).
For two bearing generators
-Remove the key (223) from the shaft extension
-Remove the screws fixing the the inner cover of the D.E. bearings (131)
-Remove the screws fixing the D.E. shield (4) to the main stator assembly
-Remove the D.E. shield (4). During this operation it is necessary to sustain the main rotor (3) of the generator in order to avoid it falling
heavily on the stator
-Remove the screws (grains) fixing the rotating lubrication valve (132) to the shaft, and then remove the lubricating valve
-Remove the rotor (3) from D.E. side. During this operation it is necessary to sustain the main rotor (3) of the generator in order to
avoid it sliding on the stator.
For single bearing generators:
-Remove the screws fixing the D.E. shield (4) to the main stator assembly and remove the shield. Remove the rotor (3) from D.E. side.
During this operation it is necessary to sustain the main rotor (3) of the generator in order it will not slide on the stator.
In case of dismantling completely a bearing, a proper puller has to be used: the arms of the puller must be placed in order to act on the
internal ring of the ball bearing or on the inner cover of the bearing (where present).

4.4. Reassembly operations

Carry out the operations described above for dismantling in reverse order. If the end-shield have been removed, the fixing screws have
to be fixed with LOCTITE (on the threaded surface).
If a bearing was removed, always install a new one.
To make assembly easier, the bearings should be heated to about 70-80 °C.
PLEASE NOTE: bearings should be assembled with the utmost care in order not to damage them.

5. VOLTAGE REGULATOR

The generators are provided with automatic voltage regulator (AVR).
The AVR is provided with potentiometers to adapt the characteristics of the AVR to the different operating conditions.
The AVR is provided with adjustable stability circuitry to allow operations in a wide range of applications.
The AVR is equipped also with protecting circuit allowing the generator to operate underspeed if not loaded.
WARNING: it is not advisable to have the generator operating loaded when the frequency (speed) is below the rated value:
this kind of operation is an overload for the whole excitation system of the generator.
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