IDEC to ABB VFD

[oldnerd 3]

I have a project where I need to connect an IDEC Smart Axis I/O 40 PLC to 2 ABB ACS 355 VFD drives. The IDEC PLC has an on board Ethernet port but I can find little information on how to program the commands over Ethernet from the PLC to the drives. I have never worked with IDEC before any advice from you  experts would be most helpful.

Thanks in advance.

Old Nerd

[Controls Guy 0]

One of the [very] few things Idec does well is master Modbus.  (At least RTU, I think TCP works similarly iirc).  There is a table you go and fill out to map slave addresses to D registers in the PLC; then the polling happens transparently, without you having to do any handshaking or interlocking in ladder.  You just read and write the mapped registers as if the drive memory were part of the PLC memory.  Very clean.

Now to operate the drive, you need to look at the state machine documentation that you'll find in the manual for the comm module, in your case a FENA if I'm not mistaken.  You send a sequence of various integers to the command word, and when a given bit in the status word goes high, you send the next integer in the state machine.  Eventually the drive turns on.  You write a different integer to turn it off.   To control the speed, you write a value (I think think 0-20000 corresponds to the min to max speed range set in the drive parameters, typically 0-60Hz).  You get back a status bitpacked word and a speed feedback word.  You can configure additional status words to appear in Modbus registers 40003-40012 or so, but you can also access any parameter directly, for example you can get parameter 1.07 by reading Modbus 40107.  Since you can grab up to 64 registers in a read*, and since almost anything you'd want to monitor is in group 1, you might as well grab all 64 from there, rather than 10 or whatever ABB wants to give you slots for in the 400xx range.  The only two issues with this are that there are some register values in the middle of the range that don't correspond to valid 1.xx parameters, and instead of returning 0's, ABB will fault on an invalid address, which forces more than one read to get all of them, AND, your read of the operating values cannot now be contiguous with the status word and speed feedback, like it can if you use the 400xx mapping (group 53 I think).

Final note:  Dump the 355's.  They're cheap, plastic, made in China from toxic drywall, garbage.  Use at least a 550.  Thank God I've never installed one, but of the ones I've seen others install, FAR too many of them fail, and ABB's response, unlike their excellent support for the 550/800/880, etc., is underwhelming.

*Normal Modbus masters can typically grab 120-125, but Idec feels compelled to let everyone else lead, so they can only do 64 and have no plans to fix this.

Caveat:  I have done Modbus/TCP using a FENA on ACS-800s for example, but have more experience with RETA's ("R[aisin]" series comm cards vs. "F[ig]" series) and the internal Modbus RTU on 550's, so some of what I've presented here might actually be specific to that config.

[UniMAT 0]

learn much