Good morning, everyone. I’m here again with yet another topic. Today, I would like to understand how I can set up my CODESYS project and what I need in order to change the frequencies of my inverters (I have three of them).
I want to communicate via Modbus. I know how to set it up, but I don’t understand which blocks to use in CODESYS (I’m programming in LD) and how to send signals from the PLC to the inverters — to start/stop them and to change their frequencies.
This depends largely on the VFD and how it is configured.
In general, many use a similar CiA402 pattern which for the simple version is:
Word0 - Bit0 = Run
Word0 - Bit7 = Fault Reset
Word1 = SpeedRef (may be Hz and usually 10x or 100x)
Status =
Word0 - Bit0 = Ready
Word0 - Bit1 = Running
Word0 - Bit3 = Fault
Again, these can vary drastically depending on VFD. Open the manual (and supplementary comms manual if applicable) for your VFD and read their comm tables. Some do not have a specific comm table if they allow config of the data (like an Altivar in SoMove for example).