Hi everyone,

I need your help, I have 3 Danfoss VLT drive that has a "FIELDBUS FAULT [W34]" which is connected to a S7-CPU,

I already replace all the profibuss cable to make sure its not a loss connection on the profibuss.

The danfoss VFD is still running but the speed is frequently fluctuating.

Hello franklanit,

could you share the diagnostic information stored at the PLC with us?
Or is your issue solved.

Best regards
Sabine

Dear hulz

The alarm on the PLC is external fault.

Hello frank;

There is an excellent tool on S7 PLCs called the diagnostic buffer, where the CPU's operating system logs messages when it discovers issues that affect the PLC operations. I believe that this was what Sabine was asking about in her earlier post.

If you have access to the programming software for your PLC, go online and open the diagnostic buffer ot see what messages you can find relating to a Profinet connection problem with your drive. Save the buffer and post it here (there is a button on the buffer page to save the file in .txt format) and attach it here if you have trouble understanding the messages.

Now, we can try looking at diagnostics form another source: here is some information from Danfoss and Danfoss users on the Fieldbus error W34:

Troubleshooting FC Programming Guide

Look at page 212, extract as attachment below. This seems to indicate that the Profinet interface card on the drive is not installed or parameterized properly.

Maybe the links below can provide a bit of information; if not, you should contact Danfoss directly.

Danfoss Warning 34 Fieldbus Fault — InControl

IM151-8 Bus Fault when using Danfoss FC302 and Profinet

faulty profibus net with danfoss fc302 - PLCS.net

Hope this helps,

Daniel Chartier

Hello Sir's.

Maybe I need to replace the VFD,  but encountered problem when removing the profibus grounding. When I remove the grounding all connected VFD is having an alarm.

SEE ATTACHED PHOTO.

Hello frank;

That is quite normal behavior.

Grounding Profius cables protects the bus from EMC (electromagnetic compatibilty) and interference voltage issues. Removing the ground connection can cause a lodss of signal transmission to the node.

See the extract below, from the first link in the following suggestions:

PROFIBUS Network Manual - Industry Support Siemens

A short guide to addressing EMC on PROFIBUS - Procentec

PROFIBUS Installation Guideline for Cabling and ... - Profibus Centre

Hope this helps,

Daniel Chartier

Hi Daniel,

Should I need to connect the profibus shield to the main grounding of the control room before disconnecting it on the VFD?

Thank you. 

Hello frank;

This might be presumptuous, but I would expect every cabinet in your electrical and controls room to be already grounded to the plant's main ground line. That would be standard industrial  installation for electrical and electronic equipment housings.

If that is the case, then your present drive grounding should already be linked to the main plant ground through the cabinet body.

Hope this helps. 

Daniel Chartier 

Hi Daniel,

Is there any software used to analyse the status of Danfoss VFD?

Your immediate response is highly appreciated.

Hello frank;

I am not a Danfoss specialist. And there is much information missing in your posts concerning your actual drive models for any of us to give you valid replies.

However, searching on the web with the search term 

" danfoss drive diagnostic software " will show you download ble PC Software for different models of Danfoss drives. Alternatively, contact your Danfoss rep or look up the Danfoss website.

Hope this helps, 

Daniel Chartier