Altivar 66 Being Controlled by Modbus+

[Wirestu]

All,

We have a site that has multiple Altivar 66's that are being controlled by an old Square D Modbus+ network. One of the VFD's has failed. What would you recommend as the upgrade path for just the one VFD.

Thanks in advance.

:site:

 

[Corsair]

My guess for why you haven't gotten a reply yet is that nobody knows what to do with Modbus Plus except throw it out. Modicon support of it on products is probably about completely gone. It's been well over 20 years since we've done anything with Modbus Plus and I thought it was on the way out then.

It was a RS-485 thing with irritating cabling components and requirements. It probably saw more use than Square D Synet but a lot less use than AB Data Highway Plus. AB probably may have had the lowest baud rate but the best network utilization. Synet and AB used pretty blue cable. AB termination was easy. Synet connectors were a headache.

Where I come from there's a saying about futile efforts - pounding oats up the *** of a dead horse. I wish I could be more positive in your situation.

 

[kenschunk]

First, you're not going with Modbus+ unless you go the second (or third) hand hardware route.

Your hands are going to be a little tied unless your PLC has Ethernet in some form. You could use a TCSEGDB23F24FA (doesn't that part number just roll off the tongue) which is a Modbus+ Proxy module for the M340 and M580. It's designed to allow M340's (and 580's) connect to a MB+ network, but it will route data the other way. It does stupid things with the unit ID in the encapsulated Ethernet packets, so it actually wouldn't work with a Schneider ATV71 VFD (also obsolete) because - Schneider. I haven't tried it with a AVT630/930 etc. yet. Message me if you'd like details.

In theory it would allow you to replace the ATV66 with a different drive that can speak Modbus TCP. You'll have to change the register addresses and scaling in the original PLC to match what the new drive needs. Again, I tried it with an ATV71 and it didn't work due to stupid programming decisions in the Proxy module firmware. That was years ago - maybe they fixed that. Ha! We know they didn't.

You could perhaps use serial Modbus communications from the old PLC, assuming you've got a Modbus port to spare on the PLC.

Now, if you're desperate and need a hack and slash solution that you never heard me say:

Wire digital and analog IO from one of the drives that still works to a new drive and modify the PLC program to control and monitor the IO in the existing drive to control the new drive. Start/Stop, speed command, running feedback - what more does a guy need?

Come on - we've all seen worse!