Manual 35092
2301E-HT Hydro (Francis Turbines)
Woodward
24
Figure 3-6. Pond Level Control Accuracy
For example, assume the control is configured for Pond Level control. The “Maximum Gate Position” has
been configured for 100% and the “Minimum Gate Position” has been configured for 20%. The “Desired
Control Accuracy” has been configured for 0.5 feet. If the level error (level set point - actual level) is
greater than +0.5, the gates will close to the minimum gate position (20%). If the level error is less than
–
0.5, the gates will open to the maximum gate position (100%). As the actual level approaches the set
point and the error is reduced, the gate position will find an equilibrium value along the curve shown
below. The only time the level error will be zero is when the equilibrium point falls on the midpoint of the
“Minimum” and “Maximum” gate position values.
The smaller the “Desired Control Accuracy” value is, the steeper the slope will be on the above graph.
This will result in a very high “gain” on the gate position, and small error fluctuations in the Pond/Tail
Level will move the gates very quickly. The “Desired Control Accuracy” value should be made as large as
possible for each given application.
First Control Mode
It is possible to choose which control mode the control will assume just after the breaker is closed. The
options are position control, baseload control, level control or remote baseload control. One of these
controls will be enabled after the breaker closes and it is possible to switch between these control modes
at any time.
Valve Driver (Gate)
The 2301E-HT digital c
ontrol’s valve driver can be configured for many different applications. The valve
driver (actuator output) can be configured as a proportional signal or as an integrating signal.
For explaining purposes, let us suppose that the actuator output has been configured for 4
–20 mA.
A proportional signal is a 4 to 20 mA signal that is proportional to the actuator set point, 0 to 100%. The
proportional signal is 4 mA for 0% gate position, 12 mA for 50% gate position, and 20 mA for 100% gate
position. No gain or offset adjustments are available in the 2301E-HT when a proportional signal is
supplied due to the nature of the signal.
An integrating signal is a 4 to 20 mA signal that positions a proportional valve, or pilot stage valve. The
integrating signal is about 12 mA to center the proportional, or pilot stage, valve. When the current is less
than 12 mA the valve moves one way, and when the current is greater than 12 mA the valve moves the
other way. The further the signal is from the null current, the further the proportional valve plunger moves
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