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 TM 55-1905-223-24-3
FIGURE 4-5. AVR Auxiliary Board.
in the approximate left center of the auxiliary board. The hole is below a rectangular red capacitor on the auxiliary
board. The AVR gain control is preset and sealed. Normally, the AVR gain control should not be adjusted. If the
voltage is unstable after a block load reduction, turn the AVR Gain control counter-clockwise. Any gain
adjustment affects the generator output voltage. Reset the output voltage after any AVR gain adjustment. Turn
the AVR gain clockwise if rated voltage cannot be obtained by means of the coarse and trimmer voltage controls.
(6)
The excitation overload (3) is a manufacturing adjustment. It is factory calibrated and sealed. Normally the
excitation overload control should not be adjusted. Turning the excitation overload control clockwise raises the 60
volt protective circuit trip voltage.
(7)
The Under Frequency Roll Off (UFRO) knee point (4) is preset and sealed at 97% (58.2 Hz and 48.5 Hz) ofated
r
frequency. Normally, the UFRO knee point control should not be adjusted. Turning the UFRO knee point control
clockwise raises the frequency at which voltage becomes dependent on frequency. If the unit is operated on the
UFRO slope, the generator output voltage will change with temperature as well as with frequency.
(8)
The voltage dip limit (5) (top right square potentiometer) is preset and sealed at approximately 30 percent of the
operating voltage. Normally, the voltage dip limit control should not be adjusted. Turning the voltage dip limit
control clockwise increases the voltage dip on large load pickup. This will make it easier for the engine to pick up
load. Turning the control counterclockwise reduces the voltage dip (makes the AVR "stiffer"). The engine may
not be able to pick up the load if the voltage dip limit is set too far counterclockwise.
(9)
The dwell (recover time delay) (6) rectangular, 20 turn potentiometer is preset and sealed at the maximum (full
clockwise) position. Normally, the dwell control should not be adjusted. Turning the dwell control counter-
clockwise will reduce the dwell time and make the voltage return to rated value quicker.
(10)
The VAr/P.F. sensitivity (7) potentiometer adjusts the response of the AVR to the signal from a VAr/P.F.
controller. This control has no effect on the AVR unless a VAr/P.F. controller is used. The control is set at
midrange.
4-20
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