Rockwell Automation Allen-Bradley LiquiFlo 2.0, User Manual

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Rockwell Automation Publication D2-3518-4 - January 2020 95
Parameter Descriptions Chapter 9
Bit 3 – Ramp Ref
• Enables/disables ramping the reference used from PI Feedback to the
selected PI Reference.
Bit 4 – Zero Clamp
• Enables/disables option to limit operation so that the output frequency
always has the same sign as the master speed reference. This limits the
possible drive action to one direction only. Output from the drive is from
zero to maximum frequency forward or zero to maximum frequency
reverse.
Bit 5 – Feedback Sqrt (Square Root Feedback)
• Enables/disables the option of using the square root of the feedback signal
as the PI feedback.
Bit 6 – Stop Mode
Bit 7 – Anti-Windup
Controls the PI regulator. Note that you must use a datalink to write to this
parameter interactively from a network.
PI control allows the drive to take a reference signal (setpoint) and an actual
signal (feedback) and automatically adjust the speed of the drive to match the
actual signal to the reference.
Proportional control (P) adjusts the output based on the size of the error
(larger error = proportionally larger correction).
Integral control (I) adjusts the output based on the duration of the error. The
integral control by itself is a ramp output correction. This type of control gives a
smoothing effect to the output and continues to integrate until zero error is
achieved.
By itself, integral control is slower than many applications require, and therefore,
is combined with proportional control (PI).
The purpose of the PI regulator is to regulate a process variable such as position,
pressure, temperature, or flow rate, by controlling speed.
There are two ways the PI regulator can be configured to operate (see parameter
124):
125 PI Control
Range: See Figure 41
Default: See Figure 41
Access: 1 Path: Speed Command > Process PI
See also: 124...138