Rheostat For Remote Voltage Setting - MarelliGenerators MJB 160 Instrucciones Y Advertencias De Seguridad

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 occured: it can range from 10s minimum to some minutes maximum.
In the workshop the potentiometer is set in the way the said limitation comes into operation only under extreme
overexcitation.
STAB - Potentiometer for stability adjust.
By rotating it clockwise stability increases, but response time becomes larger.
⇒ increase response time, increase stability
Use of micro switches
To change the stability characteristics of the regulator, it is possible to use the microswitches.
In such a way it is possible to insert capacitors on electronic stability circuit, then obtaining step changes in the transient response of
the regulator.
dip 1
pos.ON ⇒ transient response becomes faster
dip 2
pos.ON ⇒ transient response becomes faster
dip 3
pos.ON ⇒ Proper setting of the excitation limiter IT
MUST ALWAYS BE KEPT IN ON POSITION
dip 4
pos.ON ⇒ standard low speed protection
SLOPE - Potentiometer for changing the slow speed protection characteristic slope.
With this potentiometer, we can increase or decrease the under speed ramp slope, and set the voltage droop for a fixed reduced
speed. Setting with SLOPE is possible only with dip 4 OFF.
⇒ increase voltage
PAR - Potentiometer for changing the droop
In order to obtain a correct sharing of reactive power, when two or more generators are required to operate in parallel, it is
necessary to verify that the no load voltage is the same, that the bridge between "A-B" is open and the voltage droop is the
same for all generators when loaded.
When this unit is inserted the output voltage should show a 4% voltage droop when passing from no load to full load 0.8 p.f.
If the voltage is increasing as the load increases, it is necessary to reverse the leads of the current transformer at the terminals
"A-B". If necessary, the voltage droop can be reset by acting on the internal potentiometer.
In single operation the terminals A and B have to be shorted.
⇒ increase droop

6.2 Rheostat for remote voltage setting

For all generators, that rheostat can be inserted between the auxiliary terminals P and Q (FAST-ON terminals). The external rheostat
has to be inserted with its wiper in intermediate position and then the internal potentiometer of AVR (P1) has to be reset to obtain about
the nominal voltage. Rheostat features must be minimum rating 0,5 W, resistance about 100 Kohm.
SIN.UM.017.11
⇒ decrease response time, decrease stability
pos.OFF ⇒ Only for setting of the excitation limiter: it permits to
disable the normal limiter time delay
pos.OFF ⇒ proportional low speed protection V/f (see "SLOPE"
potentiometer
⇒ decrease voltage
⇒ decrease droop
29
ENGLISH