Hello,

your hardware seems to be strange... G120C with CU250S-2? This is not possible. A G120C has the control unit and power module combined. So a CU250S-2 is not possible with G120C, only with G120 modular drives.

And maybe I do not understand the question correctly, but the drive knows its speed either from its connected sensor (motor encoder) or from the internal calculated motor model (in case of sensorless vector control). Then it is just a calculated value but for closed loop control it is quite realistic.

The PID control can be done wherever you want. Maybe depending on where the actual value comes from (PLC or drive) I would try to realize it on that system to avoid deadtimes in communication. If you read in the actual value for the controller inside the drive you could use the PID controller of the drive. If you read it in the PLC, you can use the controller there.

Hello,

if you just want to control the drive by enabling it and giving a speed setpoint I would do the whole control via PLC with standard telegram 1 and SINA_SPEED function block for PLC. The block is part of the DriveLib, which is installed to TIA automatically when Startdrive package is installed. Otherwise you can download the library here:

https://support.industry.siemens.com/cs/ww/en/view/109475044

I think this is the easiest way to begin with the communication and the drive functions.