Troubleshooting And Interventions; Electrical Faults - MarelliMotori MXB-E 180 Serie Manual De Instalación, Funcionamiento Y Mantenimiento

To this purpose, you need to implement the layout shown in the previous figure, performing the following
operations:

Disconnect from the regulator the two white FAST-ON terminals (+) and (-) connecting the regulator to
the exciter stator.

Power these two terminals with the direct current source, arranging a R rheostat in series.

To regulate the alternator output voltage, operate the R rheostat.
As the load increases, compensate by manually increasing the excitation. Before decreasing the load,
reduce the excitation.
Use the following table to choose the appropriate rheostat:
Generator
MXB-E 180

8. TROUBLESHOOTING AND INTERVENTIONS

8.1 Electrical faults

MALFUNCTION
The alternator is not excited.
The loadless voltage is lower
than 10% of the nominal one.
The alternator does not excite
(loadless voltage around 20%-
30% of the nominal one).
The intervention of the voltage
regulator on the potentiometer
has no effect on the voltage.
Voltage with load lower than the
nominal one (voltage between
50 and 70% of the nominal
one).
Too high voltage.
Unstable voltage.
963857252_=
I max [A]
5
POSSIBLE CAUSE
a) Breakage of the connections.
b) Failure on the rotating diodes.
c) Interruption in the excitation
circuits.
d) Too low residual magnetism.
a) Intervention of the fuse.
b) Breakage of the connections
on the exciter stator.
c) Wrong supply in the excitation
circuit.
a) Speed lower than the nominal
one.
b) Voltage potentiometer not
calibrated.
c) Fuse failed.
d) RDT failure.
a) Potentiometer V not calibrated.
b) RDT failure.
a) Variable Diesel revolutions.
b) Stability potentiometer of the
not calibrated RDT.
c) RDT failure.
Max rheostat resistance [Ω]
INTERVENTION
(always to be performed while the machine is
not running)
a) Check and repair.
b) Check of the diodes and replacement if
interrupted or in short circuit.
c) Continuity check on the excitation circuit.
d) Apply for an instant a voltage of a 12Volt battery
connecting the negative terminal to the
RDT and the positive one through a diode to the +
of the RDT.
a) Replace the fuse with a spare one. If the fuse
trips again, check whether the exciter stator is
short circuited. If everything is normal, replace
the voltage regulator.
b) Continuity check on the excitation circuit.
c) Swap the two wires coming from the exciter.
a) Check of the number of rounds (freq.).
b) Rotate the potentiometer until the voltage returns
to the nominal value.
c) Replace the fuse.
d) Disconnect the voltage regulator and replace it.
a) Rotate the potentiometer until the voltage returns
to the nominal value.
b) RDT replacement.
a) Check of rotation uniformity and of the Diesel
regulator.
b) Rotate the stability potentiometer until voltage is
steady again.
c) RDT replacement.
Fig. 17
80
–
of the
45