2-122 Process PI Loop
• Feedback Square Root - This feature uses the square root of the
feedback signal as the PI feedback. This is useful in processes that
control pressure, since centrifugal fans and pumps vary pressure with
the square of speed.
The PI has the option to take the square root of the selected feedback
signal. This is used to linearize the feedback when the transducer
produces the process variable squared. The result of the square root is
normalized back to full scale to provide a consistent range of
operation.
The option to take the square root is selected in the PI Configuration
parameter.
• Stop Mode (PF700 Only). When Stop Mode is set to “1” and a Stop
command is issued to the drive, the PI loop will continue to operate
during the decel ramp. When set to “0” the drive will perform a
normal stop.
• Anti-Wind Up (PF700 Only). When Anti-Windup is set to “1” the
PI loop will automatically prevent the integrator from creating an
excessive error that could cause loop instability. The integrator will be
automatically controlled without the need for PI Reset or PI Hold
inputs.
PI Output
Spd Ramp
+
+
PI_Config
.ZeroClamp
Spd Cmd
≥
0
+32K
-32K
+32K
-32K
0
0
Process PI
Controller
Linear
Ramp
& S-Curve
Spd Ref
PI Fbk
PI Ref
-100.0 -75.0 -50.0 -25.0 0.0 25.0 50.0 75.0 100.0
Normalized Feedback
Normalized SQRT(Feedback)
-100.0
-75.0
-50.0
-25.0
0.0
25.0
50.0
75.0
100.0
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