powerflex 40 drives and modbus RTU

[nstn8 0]

Hello all, I am new to setting up new equipment and have been tasked with setting up a SLC 5/03 with a 3-5 powerflex 40 drives so that their speed can be adjusted from a panelview plus 1500. Currently this system is in mid upgrade position with the SLC 5/03 already there and 1 powerflex 40 drive running directly off of the SLC output card, and the rest of the system is still straight out of the 1940s with contactors etc. I was looking at ways to network the powerflex's with the SLC and from the manual for the pf40 it says "PowerFlex 40 drives support the RS485 (DSI) protocol to allow efficient operation with Rockwell Automation peripherals. In addition, some Modbus functions are supported to allow simple networking. PowerFlex 40 drives can be multi-dropped on an RS485 network using Modbus protocol in RTU mode." I am not 100% sure what this means or how to go about setting this up. I assume this means they can be networked without using DeviceNet, ControlNet, or Ethernet/IP. Can somone give me a little insight on Modbus RTU and what tools are needed to implement it?

[Ken Moore 23]

You are going to need a ModBus card for the 5/03, do you have an open slot? You can order the Modbus card from any AB dealer, check it out here: http://prosoft-technology.com/content/view/full/135

[nstn8 0]

Yes I have an open slot on the SLC. Dumb question, but does AB not make a card for this? I mean I am trying to talk to an AB drive from an AB PLC, and I have to use another brands card to do this? I'm gonna read the manual and see if I have any more questions... thanks for the link.

[nstn8 0]

Ok... i've delved into the topic a little bit deeper. After looking further it seems like a 22-SCM-232 Serial Converter Module would be an easy way to connect to the drives. This device would use the RS-232 port on my 5/03 processor. I think I can hook up a RS-232/DF1 port splitter before the 22-SCM-232 and use the one side to go to the drives and the other side to go to my Panelview Plus(2711P-T15C4D1). Does anyone have any experience doing this? Will this cut out my ability to have my panelview sent data that I want to have constantly updated? Also, extreme newb question here, but can I connect to the 5/03 from the DH 485 port for my troubleshooting from RSlogix?

[Ken Moore 23]

The convertor might get you to Rs485, but it's not going to help the SLC 5/03 speak Modbus. IMHO the prosoft card is the only solution. Prosoft is an Alliance Partner of Allen-Bradley, fits right in the rack, and comes with programming examples. Works similar to the AB scanners, you read and write to the Modbus module memory using ladder logic. ProSoft tech support is great, never had an issue they couldn't handle. The manuals are decent as well.

[paulengr 44]

Modbus RTU is a serial protocol. The actual "network media" can vary. Normally, it's RS-485, but the protocol will be just as happy crossing over RS-232 or encapsulated inside TCP/IP (in which case it is called Modbus/TCP). That being said, and talking about adding all kinds of stuff to the PLC, why? Those drives support almost any protocol you want. Just get the interface card for the DRIVE. They can do Ethernet/IP, DeviceNet, and Remote I/O, to name a few. Given your application, since Remote I/O is natively supported on SLC's and PLC-5's, I'd consider Remote I/O unless you plan on expanding a lot more in the future in which case I'd strongly consider DeviceNet. AB hasn't been supporting devices over Ethernet/IP yet with the SLC's and PLC-5's that I know of. Remote I/O is fairly easy. You just wire everything together, put termination resistors on the ends, set the rotary switches in the drives, set the parameter configurations in the drive menus (probably the hardest part) and add block transfer instructions. I had it up and running in about 30 minutes with no experience with Powerflex drives. If you go the DeviceNet route, AB made DeviceNet a total pain in the you know what to set up the first time and I'd strongly suggest having a local AB rep there to help you through the first one, but after that it's pretty simple. You'll need a DeviceNet "netmeter" (aka "happy meter") and a PC DeviceNet interface card, too, to help with setup and troubleshooting. You can also get Panelviews that interface directly into Remote I/O and DeviceNet. I don't know if it is possible to do a PLC-less system this way but I've heard rumors to that effect. Personally I've located all my operator interfaces on a separate network away from the I/O where the PLC can do "stupidity checks" (interlocks).

[swimmy67 9]

You do not need a Modbus card. you can use the DF1 communications to control the PF4 and PF40 VFD's Here iss a sample program using a SLC5/04 to PF4 and PF40 http://forums.mrplc.com/index.php?autocom=downloads&showfile=458 Hope this helps

[paulengr 44]

That works for one drive. How do you handle multiple drives? Are the node numbers (and port hardware) configurable so that you could for instance switch to DH-485 or some version of half-duplex DF-1? Otherwise, how would you handle multiple drives on one port? Do you daisy-chain the SCANports?

[swimmy67 9]

From the manual for the 22-SMC-232 converter there are sample programs in the manual. There are PLC's listed that will be able to communicate with the PowerFlex 40 Drives. Attached is the Manual that will explain the communications to the drives and the parameters required for communicating with 2 or more PowerFlex 40 VFD's 22comm_um002__en_p.pdf