Fine Tuning a PID Loop

You need to have a variable-speed motor as a replacement, not a constant-speed one.

Get another variable-speed motor.

I'm sorry, but you have GOT to give us more information.

"I have to fine tune my FIC loop that contains magnetic flowmeter and variable speed motor. Now this motor is replaced with constant speed motor "

There has to be a control element somewhere. Since you no longer have a VSD, we can only guess that you have an inlet/outlet/recirculation valve. And I hate guessing.

Was the MCC bucket setup properly (overloads) for the new motor?

"the problem is that it trips after 1 second whenever the loop is controlled on Auto mode"

Do you mean from startup, or after you already have the system running in manual, and switch to Auto?

What exactly do you mean by "trip"? Do the overloads on the MCC bucket trip? Or do you mean that the output from your system (PIC, PLC, DCS, standalone controller?), simply drop the output to the contactor coil?

It could be that there is still an artifact left from the old program, to stop the motor when the speed feedback from the VSD drops below a certain point. It could be that the output of the PID is set to 0% & does not have the necessary logic to follow what the output is when in manual, so that when you change to Auto the valve shuts.

MORE INFO PLEASE!

When operating the system from the vsd, what maximum speed did the motor run? Did you ever get up to full motor speed?

Now with the constant speed motor you are going directly to full speed, you may overload the motor (requires bigger motor or slower motor). Assuming driving a pump (with parabolic load curve) with the motor.

First, evacuate everyone in your factory. You're lack of even to most basic knowledge of forces and transforms only empowers you to eventually kill everyone you're working near.

Second, three elementals of any PID loop are the PV (process VARIABLE), SP (SETPOINT) and MV (manipulated VARIBLE). Putting contant speed motor to control a variable flow rate is analogous to using a variable frequency drive to control a lamp switch. If one is VARIABLE then the other HAS TO BE!

Go back to doing Dell and PepBoys tech support.

Never mind these guys.

Use this: P=635.565 I=128.34 D=16.787

That shoud eliminate your trouble.