I have a tool at the end of a 200m cable. Through this cable I am powering a 50kW/3,000V and a 1kW/480V motor, both with VFDs. So there is going to be a lot of noise in that cable. I need to communicate with the tool through the same cable. The comms bus conductors are 2 shielded twisted pair (3 pairs). Is there any industrial comms over copper that have a chance of communicating in the midst of all that EMI? I really don't want to use fiber optics.
What is the best data transmission protocol for high noise environment?
- Thread starter strantor
- Start date
Phil Buchanan
Lifetime Supporting Member
AS-Bus / Interface is the best for that but your are supposed to use their cable but I have seen it work on different cables at shorter distances.
Phil Buchanan
Lifetime Supporting Member
IFM Efector is normally good about bringing you some free gear to try and see if it's a good fit.
Every industrial protocol that I've seen recommends running the communication a distance away from power cables, usually at least 20cm. The fact that the comms is at least shielded TP will go a long way to help. If you need to be SURE, you go fiber, but that is def a hassle, I understand it being your last resort.
What needs to be out at the end of the cable? Just the VFDs? Are they selected yet, or will you pick drives based on the comms you choose? If you know what the drives are, and tell us what communications options you have (that your PLC supports), that will probably help people give recommendations.
Generally speaking, slower baud rate connections are more robust. In the Ethernet world, I've never heard of anyone using 10Mbaud instead of 100Mbaud Ethernet to gain EMI resistance. It probably helps in theory, but I'm not sure how well that works in reality.
Edit: My 10vs 100 example still stands, but I wasn't meaning to suggest Ethernet is an option, as the cables max out at 100m.
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AS-I is only 100 meter segments so that wont work.
But 50kW is not that much actually. I'm sitting next to a 200kW VFDs right now running a laptop over wifi. What are you going to talk to at the other end of the cable?
Are you having problems today or is it something you anticipate having?
BTW I know places that run serial RS-422 over long distances (several hundred meters) inside factories (lots and lots of VFDs and other things) without any problems.
But 50kW is not that much actually. I'm sitting next to a 200kW VFDs right now running a laptop over wifi. What are you going to talk to at the other end of the cable?
Are you having problems today or is it something you anticipate having?
BTW I know places that run serial RS-422 over long distances (several hundred meters) inside factories (lots and lots of VFDs and other things) without any problems.
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Peter Laing
Member
The node-node max cable length spec on AS-i looks like it's 100m so I'd be inclined to look at Profibus or Modbus. They both use RS485; Profibus has the more advanced protocol. You can choose a low baud rate for noise immunity if you need to. Both have lots of choices for IO modules. IFM Efector, since we're on their bandwagon these days ;-), have decent looking field rated modules for profibus. And many more...
Phil Buchanan
Lifetime Supporting Member
Putting a tuner at the end of the run gets you 200 meters.
Phil Buchanan
Lifetime Supporting Member
Putting a tuner at the end of the run gets you 200 meters.
JeremyM
Lifetime Supporting Member
What's wrong with fiber?
The motors are out at the end of the cable, the VFDs are at the source.
The power from the VFDs goes through a sine filter before going out through the cables to the motors, because of the long run (spikes).
The 50kW power goes like this: 480V/60Hz->VFD->0V/0Hz...480V/60Hz->sine filter->30Hz transformer(480V...3000V)->200m cable->motor
The 1kW power is the same, but minus the transformer
I am not trying to communicate with the VFDs; I am trying to communicate with remote I/O
I am considering Yaskawa since that's what I'm most familiar with, or ABB since they have good app notes on transformers after the VFD.
PLC is not selected yet, but I've been itching to try out the new AD productivity line. If not that, then Omron CJ2. (or whatever I'm stuck with after I drill down a protocol)
kamenges
Member
That is somewhat anecdotal evidence. On one side you have communication next to a device that is designed to prevent its power section from affecting sensitive electronics that are mounted in intimate proximity to it. On the other hand you have a conducted protocol that is basically part of an air core transformer with a 200 meter long winding. I don't know that you can extrapolate successes with the first to the second.
Keith
The application is a subsea tool. It gets (will get) rigged up and rigged down several times per month. That consists of terminating and unterminating all the cable conductors each time, and the work is performed by people who balk at the idea of landing the blue wire on the blue wire, and the red wire on the red wire. Asking these people not damage the ultra sensitive optical fibers is an exercise in futility. I do not want to get in a helicopter and fly offshore every time someone swaps the fiber connectors or steps on them and crushes them.
And before you say "but there are modular plugs" - Here's what I get for being clever with Harting connectors:
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Put an Ethernet to fibre converter at each end. I have done this in very noisy environments with the Omron CJ2 and Ethernet IP remote I./O with no issues at all. I have used these with great success. http://buy.advantech.net.au/ADAM-65...-AE/ADAM-6541-ST-AE/model-ADAM-6541/ST-AE.htm
Looks like it was mated to a hammer!
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