ABB ACQ580, Firmware Manual

Page: 61 / 422

Program features 57

Process PID control (PID/Loop controller)
There are two built-in process PID controllers (PID set 1 and PID set 2) in the drive.
The controller can be used to control process variables such as pressure or flow in
the pipe or fluid level in the container.
In process PID control, a process reference (setpoint) is connected to the drive
instead of a speed reference. An actual value (process feedback) is also brought
back to the drive. The process PID control adjusts the drive speed in order to keep
the measured process quantity (actual value) at the desired level (setpoint). This
means that user does not need to set a frequency/speed reference to the drive but
the drive adjust its operation according to the process PID.
The simplified block diagram below illustrates the process PID control. For more
detailed block diagrams, see pages
413 and 414 .
The drive contains two complete sets of process PID controller settings that can be
alternated whenever necessary; see parameter
40.57 PID set1/set2 selection .
Sleep and boost functions for process PID control
The sleep function is suitable for PID control applications where the consumption
varies, such as clean water pumping systems. When used, it stops the pump
completely during low demand, instead of running the pump slowly below its efficient
operating range. The following example visualizes the operation of the function.
Process
PID
AI1
Process
actual
values
AI2
• • •
FBA
Setpoint
Speed or
frequency
reference chain
Filter
Limitation