Troubleshooting And Interventions - MarelliMotori MXB-E 225 Serie Manual Del Usuario

internal potentiometer of the AVR to achieve the nominal voltage. Refer to the Regulator's manual.
7.2 Manual control of the exciter
If case of issues with the voltage regulator, use the alternator manually, as long as it is provided with any 24 V
continuous current supply.
The source may be a battery of accumulators or a transformer device that rectifies the output voltage of the
alternator.
EXCITER
STATOR
WINDING
TERMINALS
To this end, the diagram of the previous figure must be applied by performing the following operations:

Disconnect the two white terminals FAST-ON(+) and (-) that connect the regulator to the exciter stator.

Supply these two terminals with continuous current provided with an R rheostat.

The voltage exiting the alternator is adjusted by acting on the R rheostat.
As the load increases, compensate by manually increasing the excitation. Before removing the load,
reduce the excitation.
Use the following table to chose the rheostat:
Generator
MXB-E 225

8. TROUBLESHOOTING AND INTERVENTIONS

8.1 Electrical failures
PROBLEM
The alternator does not
energize.
The no load voltage is less
than 10% of the nominal
value.
The alternator does not
energize (no load voltage
around 20-30% of the
nominal value).
The voltage is not affected
by the intervention on the
AVR's potentiometer.
963857253_=
WHITE
24 V
WHITE
PROBABLE CAUSE
a) Connection failures.
b) Damage on the rotating diodes.
c) Interruption of the excitation
circuits.
d) Residual magnetism too low.
a) Intervention on the fuse.
b) Connection failure on the exciter
stator.
c) Incorrect supply on the excitation
circuit.
R
I max [A]
5
(to be performer always when the machine is
a) Check and repair.
b) Check the diodes and replace them if interrupted
or short-circuited.
c) Check the continuity of the excitation circuit.
d) Apply, for a moment, a battery voltage of 12 Volts
by connecting the negative terminal to the - of the
AVR and the positive one through a + diode of the
AVR.
a) Replace the fuse with the spare. If the fuse stops
again, check to see if the exciter stator is short-
circuited. If all is normal, replace the AVR.
b) Check the continuity of the excitation circuit
c) Exchange the two wires coming from the exciter
amongst each other.
Fig. 15
Max resistance of the rheostat [Ω]
80
INTERVENTION
stopped)
43