Profibus Problem at MCC

[AbrarAhmad]

Dear All,
We have connected our whole MCC panel with profibus including constant speed and variable speed motors. Today I have found that about 20 motors were giving communication problem. When these were reset they became ok. But this kind of problem frequently occurs with 2 or 3 motors giving communication problem

 

[djs]

You may have noise on the network. You really need to get a Profibus network analyizer. I suggest:

http://www.procentec.com/profitrace2/index.php3

 

[jraef]

The #1 cause of that is people making up their own Profibus cables, thinking it's no big deal. It is.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[ozmosis]

Does the communication problems only happen when the VFD's run?
If yes, then it is probably a cabling issue as jraef indicates. VFD's, as well as varying the frequency, are a good method of finding poor installation techniques and inferior cables. The problem is not the VFD btw.
If comms problems are there all the time, it could be the type of connectors/cables used but could be something deeper.

 

[cmlr]

From the information you provide it could really be a number of problems.
The specifications for the physical layer of a Profibus network are very strict, and if any of the requirements is not followed it could lead to problems.

To start you may want to make sure all components (including cables and connectors) are Profibus certified.
If they are make sure the physical dimensions of your network are within spec. Not only the total bus length is specified, also the MINIMUM length between two slaves is specified. Next step is to make sure all your bus parameters are OK.
You can check IEC 61158, or contact the experts (like procentec - see djs' post above) for more information.