MarelliGenerators M40FA640A/A MARK I, Руководство пользователя

Страница: 8 / 14

7
ENGLISH
SIN.NT.015.6 – M40FA640A/A Issued 04.2010
OVER-EXCITATION LIMITER
This function permits to limit the over-excitation due to
particular load conditions that could cause the generator
damage.
As soon as the excitation voltage rises over a certain
threshold, set by means of the potentiometer AMP, for a
time larger than the limiter time delay, the over-excitation
limiter steps-down the excitation voltage to the threshold
value.
Limiter time delay depends on the amount of the over-load:
more the over-load arisen, quicker the limiter action.
Limiting the excitation voltage, the generator excitation
level decreases, partially or totally, depending on the over-
load occurred. In case of excitation shutdown due to the
limiter, the de-excitation condition could be not maintained.
WARNING: Even if correctly set, this device does not
substitute external systems protections, it is only a
completing device.
WARNING: in case of generator paralleled with the
grid, an over-excitation condition detected by the
limiter can lead to a generator excitation shutdown,
with risk of loss of synchronism.
LIMITER SETTING:
for a quicker limiter setting, it is possible to momentarily
disable the time delay, by means of the micro-switch 3 (see
also the next paragraphs).
In order to properly set the limiter, please apply the
following procedure:
-
when the generator is running at the rated speed,
apply the maximum desired load;
- select position OFF for the micro-switch 3;
- carefully rotate counter-clockwise the potentiometer
AMP, until the yellow LED lights up and the generator
voltage decreases to a stable value, lower than the
rated voltage;
- carefully rotate clockwise AMP until the yellow LED
switches-off; the generator voltage must recover the
rated value;
- select position ON for the micro-switch 3.
If the procedure is properly carried out, the excitation
voltage threshold is set to a value 15-20% higher than the
excitation voltage at the maximum desired load, previously
applied.
Time delay depends on the amount of the over-load
occurred: it can range from 10s minimum to some minutes
maximum.