VFD Comm

[FrischEng]

I am implementing motor controls in a new treatment plant, that consists of a variety of VFD’s, Soft Starters, and across the line starters. Since this is a new plant, I am considering using communicating with my VFD’s and soft starters using Ethernet/IP rather than the digital and analog PLC I/O that I typically incorporate.

I am concerned about the reliability and the operation of motor control I/O, as I seem to remember an issue in the past, in which VFD’s ended up dumping gobs of data onto the network and were responsible for data collisions, and generally bogging down network traffic.

Can anyone direct me to a web site that reviews and/or compares the VFD’s of different manufactures, with particular interest in the Ethernet communication feature?

Would anyone like to comment on their experience communicating to drive from their plant PLC via Ethernet?

Thanks for your input.
Paul

 

[roydm]

Have not used Ethernet but used Modbus Plus and Profibus to communicate. The big advantage is simplified wiring and much more data available.
Roy

 

[ScumPunk]

There is now Profinet - sometimes described as Profibus over ethernet. Thos is designed for automation applications so should be perfect. Uses standard ethernet cabling etc. etc. Also compatible with Profisafe safety integrated layer.
Cheers,
Mort

 

[benta]

Wouldn't you normally use Sercos for VFDs?

Benta.

 

[ScumPunk]

TBH, I guess it's horses for courses:
Profinet:

http://www.profibus.com/pn/

Sercos:

http://www.sercos.com/

Profinet is certainly becoming more popular in automation, particularly in Europe.

Cheers,
Mort

 

[LionelHutz]

The VFD's should be operating as slaves on the network and only provide responses to the data that is requested.

FYI, Ethernet/IP is basically Devicenet over Ethernet.

 

[matthewm1965]

I have successfully used Profibus as the comms link between the PLCs and the drives, then linked the PLCs together using ethernet. If high speed real time control of the drives is required, then Ethernet may not be suitable. Though Profinet will overcome this failing it is not yet widely supported by all the drive manufactures.
Profibus is much more widely supported but you will need to be aware of network lenghths and number of nodes per network limitations.
Matt

 

[controlsdude]

I guess the other thing you need to wonder about is how do get your electricians to terminate all these RJ45 connectors? Does your electricians have these skills or are you doing this? Is all the ethernet connections going to a switch? Or is is daisy chained as some manufactured have brought out recently?

Easiest way to go is use a punch down box and then use a patch cable off the shelf from the punch down box to the drive.

Connections from past comms systems
Devicenet is easy to terminate
Controlnet has a predefined connection system kit
Profibus, siemens makes a vampire type connector that is pretty idiot proof and a stripping tool also.

Ethernet - looked at this one and do not see an idiot proof way except the one presently described above.

The other thing that you need to look at is the patch cable provided are straight or do you have to provide a cross cable?

 

[FrischEng]

Terminations shouldn't be an issue. I will simply make all connections with Cat-5 cables with RJ-45 connectors - just plug it in to the N-TRON managed switch on one end, and to the drive at the other end. But I havn't found any positive reviews on communication directly to VFD's, so I mulling over other options.

 

[roydm]

A data link is the only way to go if you have a number of VFDs, for just one or 2 it's probably more cost effective to use regular analogs and discretes.
I doubt speed is an issue unless you were doing something like a paper machine, even RS-485 is fast enough for most applications.
Roy

 

[FrischEng]

Does anyone know of any company that reviews/compares the different VFD brands?

 

[itsmoked]

Nope, none I have heard or seen..

But you are hijacking your own thread which means that people who may have the answer to this question may never see it as they decided this thread didn't require further input from them or wasn't of interest. Different questions deserve different threads.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ozmosis]

I've never seen softstarts on Ethernet/IP. Not to say there aren't any but it would be unusual in my opinion. Ethernet/IP is fast data transfer pushing lots of information over a TCP/IP network. It is commonly used where synchronisation is called for and therefore Mbit traffic. I'm wondering if you really need Ethernet/IP and would be better looking at MSTP based communications such as Modbus, Profibus, Devicenet.
Check your PLC's on site. If you have A-B, then Devicenet might be better or if Siemens then Profibus. Others will have both.
If you are worried about the integrity of your communications, keep it simple.

 

[ScumPunk]

Itsmoked,
Sorry but FrischEng was actually repeating a question asked in his OP. It seems to have been missed as the thread has developed. It's strange how these things evolve
FrischEng: I've been looking for some comparison data without success, I think you need to assess each system against your current (and future) requirements. It sounds like a fairly complicated installation, it might be a good idea to get all the hardware from the same manufacturer - I would imagine that any support you may need would be easier that way.
Cheers,
Mort

 

[roydm]

I had some issues with Siemens and Profibus. The small drives had this little black box that plugged on the front, Sometimes after a power failure I had to unplug and re-plug the box on each drive before the network would recognize them. It may have been a driver issue, I had to write my own as Siemens didn't have one for the S7-400 at the time.
Modbus, Modbus plus and Profibus are daisy chain so all your cables need to be OK whereas Ethernet would be Star if that makes a difference.
Something else to consider is troubleshooting tools, is it easier to communicate with a laptop (or terminal) to one over the other?
How will you configure the drives, from a PC or individually.
Do you have a control system picked out yet?
I would do a spreadsheet listing all the options, advantages, cost etc.
Interesting thread, keep us posted.
Roy

 

[itsmoked]

Thanks scum! I stand chagrined..

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScumPunk]

roydm,
What drives were they that you had the problems with? The current Siemens stuff now has the fieldbus integrated into the control unit, no external boxes required. Certainly, the issue you describe wouldn't get through system test and type test nowadays (hopefully).
Cheers,
Mort

 

[matthewm1965]

I spent 6 months evaluating drives from various manufacturers. The conclusion was that none of them did everything we wanted! The solution was to use the Siemens range of micromaster VFD together with ET200 range of remote i/o to provide additional i/o local to each drive. This was all hung on several Profibus networks with the idea to be able to upgrade to Profinet in the future, simply by changing the comms header units.
You may also need to consider your Emergency Stop system. Only a few drives from CT & SEW have "Safe Stop" inputs. We opted for an ASi-Safe network sitting below and communicating status up to the Profibus.
I would second ScumPunk by saying get all the major kit from one maunfacturer, otherwise when you ask for support, they will just blame the other vendors eqp. We learnt the hard way!
Matt

 

[ScumPunk]

Matthew,
Not sure if you are aware, but there is an ET200 VFD module available with full Safety Integrated functionality (Safe stop, Safe ramp down, Safe Low Speed). Power modules are 0.75W-4kW, and it plugs on to the back plane, along with the rest of the ET200 kit. Sounds like it may be the ideal solution for your application. I'm really sorry if I sound like a salesman, apologies if this is the way it looks.
Link:

https://mall.automation.siemens.com...023788&foldersopen=-2-511-512-569-&jumpto=569

Cheers,
Mort.

 

[matthewm1965]

Not sure if that was available or not 18 months ago when I was looking at the hardware design. However, we were looking at a >IP55 solution, which is why we went down the Micromaster route. Putting an IP20 drive into an enclosure makes for a much bigger footprint than an IP55 drive with integral heatsink.
Though the downside of this was having twice as many profibus nodes on the network, one for each drive and one for each remote i/o header.
Matt