Rockwell Automation Liqui-Flo 1.5 General Purpose and Vector Duty - Manual (Page 58)

4-26 LiquiFlo 1.5 AC Drive, Software Reference Version 1.2
Bit 2 - Preload Mode
• Enabled = Initializes the PI integrator to the commanded speed while the PI is
disabled.
• Disabled = The PI integrator is loaded with the PI Pre-load (133) while the PI is
disabled.
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 will be 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.
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 will continue 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):
• Process trim, which takes the output of the PI regulator and sums it with a master
speed reference to control the process.
• Process control, which takes the output of the PI regulator as the speed command.
No master speed reference exists, and the PI output directly controls the drive
output.
Note that Speed Mode (80) must be set to Process PI (2).
125 PI Control
Range: See figure 4.9
Default: See figure 4.9
Access: 1 Path: Speed Command>Process PI
See also: 124-138