MarelliMotori MARK XX Manual Del Usuario página 15

6. CONTROL BY MEANS OF EXTERNAL DEVICE
6.1. EXTERNAL POTENTIOMETER
An external potentiometer for fine setting of the voltage reference can be connected to the terminals P and Q.
This allows to:
- change the voltage set-point by means of remote control device;
- set the generator voltage reference with accuracy higher than the one of the internal regulator potentiometer
VOLT.
External potentiometer specifications are the following:
Setting range
±5%
±10%
As soon as the external potentiometer is connected to P and Q, a change in the global voltage reference of the
regulation system will occur; the internal trimmer VOLT must be set again to the rated generator voltage.
In detail: put the external potentiometer cursor in mid position, and after that, turn VOLT counterclockwise until to
reach approximately the desired generator voltage.
It's now possible to operate the fine setting of the voltage by means of the external potentiometer.
6.2. SPECIAL CONNECTIONS: EXTERNAL DC VOLTAGE SIGNAL
In particular cases, it is possible to connect to P and Q an external device capable to provide a DC voltage signal to
the regulator for generator excitation control.
This signal must be within the range 0 to +10 V (with P positive terminal and Q negative terminal).
WARNING:
the external device output connected to P and Q must be galvanically insulated.
The setting procedure is the following:
- Generator in single operation, no load, must be run.
- Set VOLT potentiometer in order to have approximately 50% of the rated generator voltage.
- Connect the external device as per following figure:
and provide a voltage V
- Set again VOLT in order to have approximately the rated generator voltage.
It is now possible to control the generator excitation by means of the voltage provided to P and Q; that control is
approximately linear within the following range:
WARNING: Always provide the voltage V
negative voltage to P and Q is forbidden, in order to avoid dangerous over-excitation. Should
you have any doubts about the connection and/or use of P and Q terminals, please contact
Marelli Motori Service.
Potentiometer specifications
100 kΩ - 1 W minimum
200 kΩ - 1 W minimum
+10 Vdc
Vext
+
-
0 Vdc
= +5 V to P and Q terminals.
ext
∆V
ext
+3 V
-3 V
P
Q
∆V
gen
-20%
+20%
BEFORE every generator start. Application of a
ext