Diesel Gen-set Operation Instructions
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Stop the Gen-set. Disconnect the battery from terminals F1 and F2 if AS440 or
AS480 is used, or terminal F+ and F- of SE350 is used. Restart the Gen-set, the
alternator shall run normally. If there is no voltage, the alternator or AVR line may
have problems. Please inspect the winding, rotating diode and AVR of Gen-set
according to procedures of excitation separation test.
5.2 Under Frequency Roll Off (UFRO)
AVR is connected to an under frequency protective circuit. Its voltage/frequency
characteristic is shown in Figure 10-2.
Figure 10-2 Characteristic of UFRO low frequency protection
UFRO control potentiometer is used to set the knee point.
Inappropriate setting will lead to the following consequences:
A light emitting diode (LED) on the top of UFRO control potentiometer is on with
load.
Voltage regulation factor is low with load, i.e. the alternator operation curve falls on
the oblique line of characteristic curve.
Clockwise rotation will reduce frequency at knee point and turn off light emitting
diode. The optimal setting should ensure that when frequency is below the normal
range, i.e. frequency of 50Hz alternator is 47Hz and that of 60Hz alternator is 57Hz,
the indicator light will be on.
5.3 Procedures of Excitation Separation Test
Inspect winding, rotating diode and AVR of alternator in the corresponding procedure
V
olta
ge
Droop is typical setting
as shown in the figure
Knee point
of curve
Clockwise regulation
Clockwise regulation
Frequency
