Before The Startup; De-Excitation Contact; Notes And Restrictions On Connections - MarelliMotori D-Vo Light Manuel D'utilisation

6. BEFORE THE STARTUP

6.1.

DE-EXCITATION CONTACT

The connection diagrams of D-Vo and of the generator often require a de-excitation contact to be installed between
the power supply (main terminals, auxiliary windings, PMG, etc.) and the P1-P2(-P3, if used) supply terminals of
the regulator. When the contact in question opens, the supply of power to the exciter quickly stops, thus ensuring
a prompt shutdown of the generator. Particularly for the applications in which the generator is coupled with a
hydraulic turbine, any load rejection (during operations in parallel with the grid) must be accompanied by a
simultaneous quick shutdown of the generator, to limit the overvoltage at the generation terminals, due to the
combined effect of the load release and of the increase in the turbine rpms.
In case of hydroelectric applications, the de-excitation contact must always be opened simultaneously
to the load rejection and/or to the disconnection from the parallel operation.
For all applications, Marelli Motori recommends that you associate the opening of the START contact with
the opening of the de-excitation contact.
The tripping of the two contacts, simultaneous to the load rejection and/or to the disconnection from the operation
in parallel with the grid, allows to accelerate the generator shutdown, to limit the overvoltage at the generation
terminals and to preserve the D-Vo regulation system.
WARNING: if the generator is in parallel with the grid, the de-excitation contact and START must be
used simultaneously to the load rejection and/or to the disconnection from the grid.
Furthermore, in case of auxiliary supply shunted from power supply:
It is recommended to use the de-excitation contact at the generator start/stop, in all the cases when the
speed increase or decrease ramp has a duration higher than 30s.
In particular, it is recommended to use the following guidelines:
•
when starting up the generator, close the de-excitation contact and power up D-Vo only after the speed has
reached at least 50% of its nominal value and the supply voltage has exceeded the value of 20Vac;
•
when the generator stops, open the de-excitation contact and turn off D-Vo before the speed reaches 50% of
the nominal value and the supply voltage is lower than the value of 20Vac.
6.2.

NOTES AND RESTRICTIONS ON CONNECTIONS

When installing and using D-Vo, you must take into account the following important notes/restrictions:
1. For all D-Vo applications, the connections must always comply with the connection diagrams supplied along
with the generator.
2. If included in the Marelli Motori diagrams, the de-excitation contact must always be used, unless otherwise
agreed upon or authorised in advance by qualified Marelli Motori technicians.
3. Any switches and/or devices that are not formally included in the Marelli Motori cannot be installed and/or used
at the D-Vo output, i.e. the exciter field, unless otherwise agreed upon or authorised in advance by qualified
Marelli Motori technicians.
4. If electromagnetic interferences (EMI) in the D-Vo application environment exceed the specific limits mentioned
in Chapter 3, the User must take care to equip the D-Vo system with the appropriate protections (shielded
cables, ferrite cores, etc.).
EMIs exceeding the specified limits may result in D-Vo malfunctions and/or in hardware damages.
5. D-Vo may be permanently damaged in case improper voltages were applied to its digital terminals.
For further information, refer to Chapter 3.
6. In case of doubts as to the signal peaks on the contact terminals due to noise, the user shall install dry contacts
(relays) near the regulator (distance ≤ 50cm); the wiring between the dry contacts and D-Vo shall be suitable
(shielded and twisted cables) and shall not exceed the length of 2m.
7. The aluminium support of D-Vo must be electrically connected to GROUND.
8. Should you need any further information about the connection diagrams and/or the components in use, contact
Marelli Motori Services before the commissioning of D-Vo.
9638571A0_C
D-Vo Light – Marelli Motori
EN 36