ABB ACS580 With AB Control Logix

[PLCENGR014]

Hi all!

I am hoping to find some help understanding the ABB VFD Connection to my Rockwell PLC.

I have set up the VFD parameters based on the provided ABB worksheet for the ODVA extended set of parameters. I have uploaded an image of the parameter settings from the ABB Spreadsheet.

My issue comes with the speed reference control however. In the PLC, I send a speed reference command over ethernet to the VFD. For example, 100 RPM. I then read that reference BACK from the VFD to verify the correct speed reference has been sent. The two should match exactly. But they don't. If I send a reference of 100 RPM, as a data type INT (as specified in the ABB documentation for the transfer) I get back a value of 1111 RPM. Now, I assume that the value is a modified value, corresponding to 111.1 RPM, which matches the other data transfers I see, so the decimal value is not my concern.

My issue is that if I tell the VFD to spin at 100 RPM, I should get a reference back of 100.0 RPM (1000). With the extra 11.1 RPM I am getting back, this throws the whole system out of tolerance.

So, I am wondering if there are any ABB & Rockwell experts out there who can enlighten me on where the extra 11.1 RPM comes from, and how I can scale or remove it to get my references sent and received to match!

Thanks in advance!

 

[widelto]

Are you using an encoder with your drive motor configuration ?

 

[PLCENGR014]

No, there is no encoder on this system. And to clarify, the return reference is not the 'actual speed' of the system. It is the VFD's control reference command. In essence, it is checking to ensure that the Commanded speed in the PLC matches the commanded speed in the VFD's control algorithm.

 

[PLCENGR014]

I found my solution, and it is about as dumb as I expected. The return data is scaled on a 0-20000 basis. So I just needed to scale the data to match my 0-1800 RPM format.

 

[chelton]

I found my solution, and it is about as dumb as I expected. The return data is scaled on a 0-20000 basis. So I just needed to scale the data to match my 0-1800 RPM format.

When you have the drive in the default "scaler" or "V/hz" mode the drive reference and feedback are calculated from the motor "synchronous speed".
If you change the drive to vector mode you reference and feedback are 1:1 rpm units.
Here's a link to the manual.
FEIP-Manual