Sensing Voltage; Stability Adjustment; Under-Frequency Protection - WEG K38L Manual De Instalación, Operación Y Mantenimiento

6.4 SENSING VOLTAGE

The AVR uses the sensing voltage as reference to increase or decrease the excitation on the alternator
field, thus maintaining the output voltage stable. The voltage range should be selected by the dip switch
SW2 and it must be compatible with the rated voltage of the alternator.
SW2 E1(ON) position: Sensing voltage must be within150 and 300Vac.
SW2 E2(OFF) position: Sensing voltage must be within 300 and 600Vac.
ATTENTION!
The incorrect selection of the sensing voltage range will cause
malfunction and can cause serious damage to the equipment and the
!
entire installation.
Consult our technical support in case of questions.
This installation should be performed only by qualified personnel.

6.5 STABILITY ADJUSTMENT

To ensure a good operation performance of the alternator even when facing abrupt load variation, K38L
employs an efficient circuit to control stability. The correct setup is achieved starting the generator without
load, at the nominal frequency and voltage, and then slowly turning the STAB potentiometer counter-
clockwise until the alternator voltage starts to get unstable. The ideal setting is found turning the STAB
potentiometer slightly back until it reaches stability again but as close as possible from the instability
zone.
6.6 U/F UNDER-FREQUENCY PROTECTION
K38L employs a sub-frequency protection circuit, which is capable of providing a V/HZ Constant feature.
When the alternator frequency goes below a predefined threshold, the voltage also starts to decay hence
protecting both the AVR and the Alternator against over field current. This feature avoids the need to turn
the excitation off when stopping the generator, due to the fact it decays 8 volts per Hz. The U/F
potentiometer determines the U/F trigger frequency, being predefined from factory. However, 50/60Hz
selection, via the dip switch SW1, is still necessary.
Automatic Voltage Regulator - K38L | 9
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