This is ages ago - but IIRC, we did it something like this Motor - VFD - PLC - OPC server - OPC client The .NET Application worked purely as a GUI read/write

This is ages ago - but IIRC, we did it something like this Motor - VFD - PLC - OPC server - OPC client The .NET Application worked purely as a GUI read/write data from/to the PLC. But of course there were other things involved, like database programming, API service, webdev. We made a very, very simple API in ASP.NET I think, and some website in PHP which would just plot the various motor values.