MarelliMotori D-Vo Light Manuel D'utilisation page 33

Underexcitation (UEL)
9638571A0_C
I
EXC_MAX
I
EXC_C
T
D
The function can be enabled/disabled:
If enabled, it is active in all operating modes.
Even when it is disabled, D-Vo limits the maximum field current that can be
supplied to the set maximum allowed value, I
D-Vo can limit the underexcitation, to prevent any demagnetising effects and
losses of synchronisation during the operations in parallel. When this function is
active, D-Vo senses the demagnetising type reactive power and limits any
ensuing decrease of the field current.
-100 -50
In the P-Q power diagram (P active power, Q reactive power), the underexcitation
limiter tripping area is delimited by a curve defined by 5 points, whose P-Q
coordinates can be set through D-Vo Dashboard.
With reference to the figure above, the light-blue section is the area within which
the generator cannot operate; the limiter trips by limiting the exciter field current
so as to ensure that the working point remains within the permitted area (orange).
The switching of the limitation to active state is signalled by a visual warning in D-
Vo Dashboard, and can be optionally associated with one of the three
programmable output relays.
Overexcitation limiter
IEXC IEXC_C
EXC_MAX
Underexcitation limiter
100
75
50
25
0
0
Underexcitation limit
Limite di sottoeccitazione
D-Vo Light – Marelli Motori
tripping time
IEXC_MAX
.
reactive power
50
EN
100
33