Underfrequency Limiter - MarelliMotori M40FA640A/A Mark I User Manual

SLOPE Setup of the low speed protection characteristic slope.
With the micro-switch 4 OFF, this potentiometer allows to increase or decrease the under speed ramp slope, and
set the voltage droop for a fixed reduced speed.
MIN MAX
Turn clockwise to decrease the voltage dip
PAR Setup of the droop.
This potentiometer allows to change the voltage droop for reactive compensation.
MIN MAX Turn clockwise to increase the droop
5.3. Dip-switches
Dip-switch 1 – Stability setup
ON:
OFF: -
Dip-switch 2 – Stability setup
ON:
OFF: -
Dip-switch 3 – Overexcitation limiter setup
ON:
OFF: Setting mode enabled
Dip-switch 4 – Underfrequency Limiter (low speed protection)
ON:
OFF: Low speed protection with V/f slope adjustment (see SLOPE potentiometer)

6. UNDERFREQUENCY LIMITER

The regulator is provided with internal circuits in order to reduce the excitation, when running at low speed, in order to avoid
damages to the excitation system of the generator (i.e. to the regulator, to the exciter field, to the rotating rectifier, main rotor).
The potentiometer FREQ fixes the corner-frequency, that is the frequency at which the limiter operates. Below that particular
frequency, red LED switches-on and the voltage of the generator reduces further together with the generator speed reduction.
By setting the micro-switch nr. 4 in OFF position, the voltage reduction is smaller and is close to be proportional to the speed
reduction (voltage reduction is adjustable by the potentiometer SLOPE).
7. STABILITY ADJUSTMENT
The voltage regulator is provided with internal adjustable stability circuits in order to allow stable operation in a wide range of
applications. The stability of the regulator can be set on field to adapt it to the characteristics of the plant and/or the driving
engine (diesel engine, water turbine, gas turbine) in order to obtain the best voltage response.
To change the stability characteristics of the regulator, it is necessary to act on the potentiometer STAB (for fine setting of
stability). An additional coarse setting of stability can be achieved by means of the micro-switches number 1 e 2.
963857132_I
Decrease the time response
Decrease the time response
Setting mode disabled – Limiter enabled
Standard low speed protection
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