MarelliMotori MEC-20 Manuel Utilisateur page 32

If the available documentation is not sufficient for solving the problem, contact Marelli Motori
Service for further instructions.
All operations indicated below are to be performed with the machine off, except where
specifically noted.
PROBLEM
With the generator
started, with no-load, the
voltage to the output
terminals is less than the
nominal value and equal
to the residual voltage of
the machine; this value
remains even after
having adjusted the
VOLT and VFINE
potentiometers.
Once the blown fuse is
replaced, there is again
a fuse interruption.
963857154_U
POSSIBLE CAUSE
There is no connection
regulator power terminals P1 and P2 and
(according to the application):
❖
the auxiliary winding
❖
the main generator
terminals
❖
the PMG output
There is no connections between the +
and - terminals on the regulator and the
exciter field.
Terminals P and Q have no jumper or
are not connected
potentiometer.
Regulator powered by auxiliary winding:
the residual voltage of the auxiliary is
insufficient for self-excitation (minimum
voltage required, 5V).
Regulator powered from main terminals:
the residual generator voltage between
P1 and P2 is insufficient for self-
excitation (minimum voltage required,
5V).
Regulator powered from the PMG: the
PMG output voltage and P1 and P2 input
voltage is insufficient for self-excitation
(minimum voltage required, 5V).
Internal fuse interrupted
Regulator failure.
Regulator failure.
OPERATION
between Check
diagram provided with the generator).
output
Check
diagram provided with the generator).
Check
to an external diagram provided with the generator).
Bring the generator to nominal speed
and measure the voltage output from the
auxiliary winding.
If this is less than 5V, increase the
residual magnetism of the generator
following the instructions in the generator
Use and Maintenance Manual.
Bring the generator to nominal speed
and measure the voltage between P1
and P2.
If this is less than 5V, increase the
residual magnetism of the generator
following the instructions in the generator
Use and Maintenance Manual.
Bring the generator to nominal speed
and measure the voltage PMG output
voltage. If it is less than 100V, contact
Marelli
instructions.
Replace the fuse.
Replace the regulator.
Replace the regulator.
connections (ref. connection
connections (ref. connection
connections (ref. connection
Motori Service for further
32