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 inthe pipe or fluid level in the container.In process PID control, a process reference (setpoint) is connected to the driveinstead of a speed reference. An actual value (process feedback) is also broughtback to the drive. The process PID control adjusts the drive speed in order to keepthe measured process quantity (actual value) at the desired level (setpoint). Thismeans that user does not need to set a frequency/speed reference to the drive butthe drive adjust its operation according to the process PID.The simplified block diagram below illustrates the process PID control. For moredetailed block diagrams, see pages 413 and 414.The drive contains two complete sets of process PID controller settings that can bealternated whenever necessary; see parameter 40.57 PID set1/set2 selection.Sleep and boost functions for process PID controlThe sleep function is suitable for PID control applications where the consumptionvaries, such as clean water pumping systems. When used, it stops the pumpcompletely during low demand, instead of running the pump slowly below its efficientoperating range. The following example visualizes the operation of the function.ProcessPIDAI1 ProcessactualvaluesAI2• • •FBASetpointSpeed orfrequencyreference chainFilterLimitation
