TM 9-6115-604-34
NAVFAC P8-633-34
e.
Electric Governor Control Unit.
(1)
The electric governor control unit is an all electric, solid state unit with a circuit board coated on both sides
with a compound to protect against vibration and humidity. The unit senses frequency signals from
magnetic pickup PUl on the flywheel housing that are proportional to engine speed and compares them
against a preselected speed reference. The unit accordingly adjusts current through the actuator L101
based on any difference between the two compared signals thus metering the fuel flow through the
actuator L101 to maintain the engine at the predetermined speed regardless of any changes in load.
(2)
The electric governor control unit is reverse acting in respect to loss of magnetic pickup PUI signal. If the
signal is lost, the control unit will position the actuator metering valve to the no fuel position.
NOTE
The speed control adjustment procedures are contained in the Operator and Organizational
Maintenance Manual.
(3)
The electric governor control unit has three adjustments (see Figure 6-30): (a) The FREQUENCY ADJUST
is a continuously variable 22-tum control for adjusting the speed setting. The control frequency range is
from 300 to 10,000 Hz. Typical magnetic pickup PUl frequency at 1800 rpm is 4260 Hz. Clockwise
adjustment increases the speed setting.
(b)
The GAIN control is a single-turn control to adjust the sensitivity of the governor. Clockwise
adjustment increases the gain. Instability will result with full clockwise adjustment while full
counterclockwise adjustment will result in sluggish control. A small frequency change may be noted
when the gain control is adjusted. If so, reset the frequency with the frequency trim potentiometer,
which is located on the panel mounted 50/60 Hz module.
(c)
The STABILITY control is a single-turn control to adjust the time constant of the electric governor
control. The time constant is the length of time required for the engine to return to set speed after a
load change. Clockwise adjustment shortens the time constant and counterclockwise rotation
increases the time constant. The STABILITY control is adjusted for the shortest time constant while
maintaining stability.
f.
Load Sharing Module A104 (see Figure 6-30). The precise loadsharing module measures the true power output
of an ac alternator and converts this output to a proportional dc voltage. By proper connection of the outputs, a
multiple arrangement of generator sets can be connected in parallel to share the load equally. The inputs to the
load-sharing unit are: line-to-line voltage, line currents, and battery supply. This module also includes load
anticipation and adjustable droop control circuitry.
g.
Instability. Instability may occasionally result when units are paralleled. Instability can be caused by the LOAD
SHARING SENSITIVITY control (Figure 6-30) being set too high. Turn the sensitivity control counterclockwise
until stability is restored. The system should stabilize with the control no more than 75 percent counterclockwise.
This must be done the same on all units. If instability is still present, the GAIN adjustment on the speed control
unit may have to be reduced slightly.
h.
Load Anticipation Adjustment. The load sharing module has a load anticipation circuit to improve transient
response. The load anticipation adjustment is factory set at zero sensitivity (full counterclockwise). The load
anticipation should be adjusted while the engines are in parallel. Carefully advance the LOAD ANTIC ADJUST
while occasionally varying the throttle position or changing the load. Instability or overshoot may result if the
control is advanced too far.
i.
Droop Adjustment. Five percent adjustable droop with load is obtainable after disconnecting the parallel cable,
and adding a shorting plug to J21, J22, or J23. The shorting plug applies a direct short circuit to the parallel
cable connection. Adjust the DROOP ADJUST control to the desired droop level. It is linear and may be set at
any load.
6-59
