Aftersales Assistance And Maintenance; Control And Check Procedures; Control Of Windings And Electrical Insulation; Control Of The Rotating Rectifier Diodes (Fb Dc, Ib Dc) - Sincro DC Serie Manual De Uso Y Mantenimiento

7. AFTERSALES ASSISTANCE AND MAIN-
TENANCE

7.1 Control and check procedures

The maintenance and fault diagnostic
procedures involve risks that may cause
severe injury or even death. These
WARNING!
procedures should therefore be carried out
solely by qualified 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.
The lack of routine check-ups and poor
maintenance can cause severe damage to
persons and/or objects.
WARNING!

7.1.1 Control of windings and electrical insulation

The condition of the windings can be checked by
measuring their insulation resistance. While running this
test disconnect the voltage regulator and EMC filter.
It is usually sufficient to control the main winding.
The readings should give a measurement of at least 2
MOhm. If the insulation resistance is below this threshold,
the alternator alone should be oven dried at 80 ÷ 100°C
for 6 hours. Before carrying out this operation remove the
voltage regulator.
7.1.2 Control of the rotating rectifier diodes (IB
DC, FB DC)
This check can be performed with a multimeter, the knob
must be selected to the position "Diode test". The lead
of each diode has to be removed from the connections
with the rotor exciter (see figure), but it's not necessary
to removed them from the alluminium plate where they are
fixed.
The faulty diode will have high (theoretically infinite)
resistance in both directions (open diode) or it can have low
resistance on both directions (diode in short) by placing
the tips on both directions. Meanwhile the correct working
diode will have low resistance in forward direction and high
(theoretically infinite) in the other (reverse) direction.
FB DC
IB DC
7.1.3 Brushes and collector (E DC, FT DC)
Expected lifetime
The lifetime can shorten drastically in the presence of dusty
environments and, especially, in the presence of sand.
Check the brushes for wear every 250 hours and
when changing the engine oil. When replacing worn
brushes, always check the state of the collector.

7.1.4 Control of bearings

During maintenance control the condition of the bearings
and check that no grease has leaked; the lifespan of the
bearings depends on the vibrations, 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.
A bearings lifespan is closely linked to the
working conditions and environment.
IMPORTANT!
Long periods of sustained vibrations can
damage the bearing balls and their seat.
Too high humidity can emulsify the grease
and encourage corrosion.
IMPORTANT!
Intense vibrations caused by the engine
bad alignment of the components in the
generating set put the bearing under
IMPORTANT! stresses that will reduce its lifespan.
of brushes: 1000h.
25