ENGLISH
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7. AFTERSALES ASSISTANCE AND MAINTENANCE
!
WARNING!
The maintenance and fault diagnostic
procedures involve risks that may cause
severe injury or even death. These
procedures should therefore be carried
out solely by qualifi ed electrical and mechanical
specialists. Before any maintenance and cleaning
work make sure that there are no live parts that the
generator housing has cooled to ambient temperature,
that the generating set cannot be accidentally started
up and that all procedures are strictly observed.
7.1 Control and check procedures
7.1.1 Control of windings and electrical insulation
The condition of the windings can be checked by measuring
their electrical resistance to earth. While running this test
disconnect the voltage regulator. It is usually suffi cient to
control the main winding.
The readings should give a measurement of at least
2MOhm. If the insulation resistance is below this threshold,
the alternator alone should be oven dried at 80 ÷ 100°C for 4
hours. Before carrying out this operation remove the voltage
regulator.
7.1.2 Control of rectifi er diodes
This check can be performed with multimeter. The lead of
each diode (1) has to be removed from the connections with
rotor exciter (see side fi gure). With this, diodes don’t have to
be removed from the aluminium plates (2) that carry them.
When measuring resistance, the faulty diode will have high
(theoretically infi nite) resistance in both directions.
If the diode is shorted, by placing the tips in both directions,
the resistance will be low.
Meanwhile the correct working diode will have small
resistance in forward direction and high in other (reverse)
direction.
7.1.3 Control of the surge suppressor
This check can be performed with multimeter. The lead of
each diode (1) has to be removed from the connections with
rotor exciter (see side fi gure). With this, diodes don’t have to
be removed from the aluminium plates (2) that carry them.
When measuring resistance, the faulty diode will have high
(theoretically infi nite) resistance in both directions.
If the diode is shorted, by placing the tips in both directions,
the resistance will be low.
Meanwhile the correct working diode will have small
resistance in forward direction and high in other (reverse)
direction.
7.1.4 Control of bearings
The bearings are sealed and maintenance free
.
During maintenance control the condition of the bearings
and check that no grease has leaked; the lifespan of the
bearings depends on the vibrations and axial strains they
undergo (vibrations can increase considerably with a bad
alignment) and on the working conditions. So check for
any unusual signs: vibrations, unusual noises, clogged air
vents.
If undue vibrations or noises appear after long-term usage,
these could be due to a worn bearing that, if damaged, has
to be replaced
The bearing should always be replaced after 20.000
working hours.
i
IMPORTANT!
A bearings lifespan is closely linked to the
working conditions and environment.
i
IMPORTANT!
Long periods of sustained vibrations can
damage the bearing balls and their seat.
Too high humidity can emulsify the grease
and encourage corrosion.
i
IMPORTANT!
Intense vibrations caused by the Motoror
bad alignment of the components in the
electricity generating set put the bearing
under stresses that will reduce its lifespan
