Water Tank VFD PID Control

Hello All,

I am currently working on Controling the water level in a tank using a PID instruction in RSlogix 5000 via VFD.

I have set my control variable as the VFD and the process variable as the level meter. Everytime I start my program the VFD stays at 0 hz and does not try to reach the set point. Any ideas on how i may be able to fix this? Below i have attached photos of how it is currently scaled and configured:



Any help is much appreciated, Thank you.

How is the CV getting to the VFD? An analog output in the PLC? If so, have you programmed the VFD to accept a speed command from its analog input? Even if so, what is telling the VFD to Run in the first place? Some VFDs can be set up to respond to the AI as a complete control signal, in that you have an AI threshold that tells the drive to run and below that it stops on its own. But you must program the drive to do that (if it even can).

PID initialized is off....how are you calling the PID block. Doesn't look like it's executing.

robertmee said:

PID initialized is off....how are you calling the PID block. Doesn't look like it's executing.

Click to expand...

Subroutine not being called?

You'll want to put the PID block inside a periodic task with a period of 150ms to match the loop update of the PID. Otherwise you may get unstable performance.