Winco DPG-2145-001 - Manual (Page 22)

Manual 36526F DPG-21XX-00X Digital Controllers
Woodward 14
Use carefully, as improper use can prevent the controller
from ever reaching the target speed. The first line of defense
in reducing over speed or under speed errors is a well-tuned
controller via the PID terms.
3.18 Integral High Limit (optional)
The integral high limit prevents "integral windup" in the positive direction. In other
words, the integral high limit parameter is used to reduce overspeed duration after a
long or sustained under speed condition was present. The high limit helps reduce the
duration and amount of engine overspeed by maintaining a maximum actuator position.
When larger PWM duty cycle values do not increase the engine speed any further but a
negative off speed (measured speed less than the target speed) remains, letting the
Integral term grow more positive is not beneficial. Unused positive integration would
cause a slower recovery from an over speed condition.
If an engine overload situation causes the engine speed to remain below the target
speed for some period of time, then the integral portion of PID output would grow larger
than otherwise needed (would windup). Therefore, when the load is removed the
engine may over speed because it takes time for the integral portion of PID output to
shrink or ―unwind‖. This is where reducing the Integral Limit High value can help by
preventing excessive windup in the PID output’s integration term.
The integral high limit specifies the PWM duty cycle where the integrator’s influence on
raising PID output must stop. The default value is 99%. The value can be adjusted from
99% down to 10% in 1% increments.
Use carefully, as improper use can prevent the controller
from ever reaching the target speed. The first line of defense
in reducing over speed or under speed errors is a well-tuned
controller via the PID terms.
3.19 Password
The Password parameter is not available on DPG-21XX-00X Series models.
3.20 Over Speed Limit (optional)
DPG-21XX-001 Models:
This parameter is used to determine the engine speed that will trigger the controller to
output minimum fuel. The parameter’s value is in terms of a percentage over the
highest set speed. In other words, an over speed condition is detected if the engine
speed reaches a speed of [OVER SPEED LIMIT %] greater than the highest set speed.
For example: If the highest set speed is 1800 RPM and this parameter is set to 20, then
an over speed condition will be detected at 2160 RPM (the value that is 20% greater
than 1800). Formula: 1.20 * 1800 RPM = 2160 RPM
The default value of 100 is used to disable over speed detection. Use values less than
100 to enable the over speed limit function and set the limit speed to
[(1 + (over_speed_limit_value/100)) * (highest_set_speed)].