Manual 02880
723PLUS/Single Engine Marine Propulsion
Woodward
77
22. This trace shows results of ultimately increasing Gain Ratio from 1.0 to 3.0
and decreasing Window Width from 60 rpm to 5 rpm. Overall peak rpm has
been reduced approx 30 rpm. The fuel demand is steeper with little
overshoot and roll-off. The speed roll-off is extended slightly by the Window
Width and Gain Ratio settings. This is normal.
23.
Begin
the Window Width and Gain Ratio adjustment process by increasing
the Gain Ratio from 1.0 to 2.0, then reduce the Window Width from 60 rpm
in 10-rpm increments. Actuate an actuator bump or load on and load off step
after each adjustment and observe the change in peak engine speed.
Initially, the window will be too wide to cause any change in peak speed.
Eventually a reduction will be observed.
Be prepared to first reduce the
Gain Ratio, or second increase the Window Width, if severe instability
occurs
due to cycling through the low gain region. Do not attempt smaller
Window Width settings if this occurs. It may be useful to set the alternate
(1st or 2nd) dynamics to produce a stable engine speed and to switch to
these dynamics should severe instability occur while setting Gain Ratio and
Window Width.
Otherwise, continue the Window Width reduction and actuator bump
response down to 10 rpm, and then reduce to 5 rpm. Reductions below 5
rpm are not recommended.
Increase the Gain Ratio as needed to obtain the desired response. The
objective is to set the smallest Window Width with the highest Gain Ratio
without going unstable. If the Gain Ratio setting that causes severe
instability is known, then the final setting should not be more than half of this
amount.
24. Eventually a point is reached where no further improvement is possible. The
fuel demand overshoot should be minimal. Reduce the Gain or Gain Ratio
as needed to reduce the fuel demand overshoot.
Gain Slope and Gain Break point Adjustments
25. Gain Slope is an adjustment that increases gain as load (fuel demand)
increases. This adjustment should not be changed from 0.0 until the
previously described adjustments have been made. While it is possible to
set a negative Gain Slope which decreases gain as load increases, it is
considered unnecessary and not recommended.
26. The objective of these adjustments is to add gain at high engine loads to
improve transient load response. If the transient load response is already
acceptable, no adjustments are needed. Otherwise proceed as follows:
27.
Set the Gain Break point
equal to the no-load minimum speed fuel
demand. The actual fuel demand minus the Gain Break point setting is
multiplied by the Gain Slope to add gain when load increases. When the
actual fuel demand is at no-load, the difference is zero, therefore zero gain
is added at no-load.
28.
Set Gain Slope
while the engine is operating at or near rated load.
Gradually increase the Gain Slope in 0.5 increments, and bump the actuator
or make a step load change to measure the transient response. Continue
this process until the desired transient load response is achieved or
excessive instability occurs. Should excessive instability occur, reduce the
setting to one-half of the setting that produced this instability.
Summary of Contents for 723PLUS
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