Rockwell Automation 20G PowerFlex 750-Series AC Drives - Manual (Page 78)

78 Rockwell Automation Publication 750-RM002B-EN-P - September 2013
Chapter 1 Drive Configuration
the drive turning the pump at the required speed, the pressure is maintained in
the system.
However, when additional valves in the system are opened and the pressure in the
system drops, the PID error alters its output frequency to bring the process back
into control. When the PID is disabled the commanded speed is the ramped
speed reference.
When the PID is enabled, the speed reference is disconnected and PID Output
has exclusive control of the commanded speed, passing through the linear ramp
and S curve.
Pressure
Transducer
PID Feedback
Motor
Pump
Desired Pressure
P1067 [PID Ref Sel]
+
+
Slip Adder
Spd Ref
PID Ref
PID Fbk
Process PID
Controller
PID Disabled Speed Control
Linear Ramp
and S Curve Spd Cmd
Slip
Comp
Open
Loop
Process
PID
+
+
Slip Adder
Spd Ref
PID Ref
PID Fbk
Process PID
Controller
PID Enabled Speed Control
Linear Ramp
and S Curve Spd Cmd
Slip
Comp
Open
Loop
Process
PID