VSD noise taking out telemetry

I've found on some of the well sites I work on that when the VSD is running the noise takes out the freewave telemetry. As soon as it stops the comms come good again.I checked the earthing of the well site,checked all the cabling of the well site (cables are all SWA as its hazardous area),ran new equipotential bonding off the drive but none of it seemed to stop the noise.It wasn't until I insulated the aerail and lighting arrestor from earth for the freewave radio that I was able to get good comms again with the VSD running.I've found that the bigger the pole the aerial is mounted on the more noise it seems to pick up.Also when the freewave has a weaker signal to its master the noise takes it out again.I have spoken to the manufacturer s for the skids for our well sites as well as the telemetry guys and no one's sure of why its occuring.What I have done is a temporary fix with insulating it from earth but was wondering if anyone had any advice on where to go from here.Thanks for your help.

What size drive and how far between drive and motor?

You can get some horrible noise from VSDs. just to confirm, the motor cable is screened?

Is the telemetry unit / radio itself also earthed? I'm wondering if the VSD interference is taking the shortest path to earth, through your telemetry unit's earthing and to the big ol' earth stake which is your antenna mast.

You sound like you are pretty knowledgeable about grounding so please don't be offended with the following basic preliminary questions:

1 As above, are the motor leads run in shielded motor lead cable?
2 Is the power floating delta? If so, a delta-wye isolation transformer is critical. The center of the wye is tied to ground and all VSD-related grounds are to be tied to the same point
3 Is there any kind of high frequency filter (line reactor or dv/dt filter) on the motor leads and if there is, is it wired directly to the VSD output?

If you don't have VFD cable then you need it. I like lapp http://lappusa.lappgroup.com/products/wire-cable/flexible-cable-for-drives-motors.html

and Belden http://www.belden.com/products/browse/industrialwc/vfd-cable.cfm

You may also need filtering http://www.transcoil.com/home.htm

As you are in Queensland, its quite possible that the soil in your area is dry and thus making the earthing not so effective.

If you are attached to the local power supply you will already have a Delta to Star transformer as DickDV refers to 11,000 to 415 Volt

But how good are your earth and Nuetral connections in your switchboard and at your earth stake
and probably more importantly are the transformers Nuetral to earth connections and earth at earth stake up to standard.

The Plc Kid said:

If you don't have VFD cable then you need it.

Click to expand...

x2

Shielded VFD motor lead cable keeps the noise in.

Shielded VFD motor lead cable keeps the noise in

Click to expand...

But it must be installed correctly, with the shield terminated at the motor end using glands made to connect the shield to the motor, and terminated correctly at the vsd end. At the vsd end the shield must be taken all the way to the vsd and must be terminated with either a gland or bracket made to terminate the shield

As Gil47 said check your ground resistance also.

Theses are the instruments that can be used to do that

http://www.fluke.com/fluke/usen/Earth-Ground/Fluke-1630.htm?PID=56021

http://www.aemc.com/products/html/view.asp?id=5&dbname=products

Many people still like the 3 or 4 point system but lab test shows that the clamp is just as good or better in some cases depending on brand.

If you want to rent vs buy then here is a good option also.

http://www.atecorp.com/categories/more/EarthResistanceMeters.asp

I'll put my replys all in the one post.The VSD is a Yasakawa F7 15KW mounted in a panel that is connected to a skid with a cable to the motor being 8 meters long.The cable is not a VSD sheilded cable but is steel wired armour that is connected to earth at both ends via the glanding.Saffa ,the telemtry gets it ground reference from the lightening arrestor and this also where the 0V for the control circuit gets it ground reference.I think this should be at the supply transformer.While insulating the lighting arrestor and pole from earth I'm worried that the noise could be corrupting data in the freewave unit as well as the PLC, but for the moment I need it running like this for the comms to work.Dick,the supply is from a generator we have put on site that is wye(star)connected with earth and neutral off the star point.We have inline filters on the line side of the VSD as well as a DC reactor connected to the VSD.I found at one site where the aerials were small and the distance between the master and slaves was 100-200m that it only affected it when we moved the master aerial the other way making for weaker signal.This shows to me the noise is always there but how to keep more of it in. This is happening at a range of different sites with the style of skid,bigger aerials and a weaker freewave signal being the common factors.Do yo guys think SWA cable is a sufficent screen for VSD cables as I have use it as it's a hazardous area?Should your power earth and 24V DC be on seperate earth bars with seperate earth stakes?Thanks again guys.

Its my belief that under the New Zealand and Australian wiring standards that we both work to, the SWA (steel wire armoured) cable can and should be Earthed, but its function is that of an armour only, and that you require a copper or aluminium conductor for the Earth Conductor.

But in saying the above I don't think with an 8 meter lead that it would make much or any difference, if it were changed,
I feel the fact that the skid is generator powered, that the noise finds the weak link to earth and that's through the tuned higher frequency link of the radio

My suggestion would be to run the radio link and maybe the 230 volt supply for 24 volt DC from a one to one,.. 230 volt isolating transformer to see if this makes a difference

With the SWA cable are you taking the Armour all the way to the VSD. If you are not this is probably a large source of the noise. To be effective the shielding must go from the drive to the motor. The VSD probably has a clamping plate that should be used to terminate the shield

Here's a compact EMC pocket guide:
http://www.ifm.com/obj/EMC-Pocket-Guide-ZVEI-english.pdf

Kalle

You can use braided cables (SY type) in hazardous areas so if you think that may be the issue,it's worth a try. In most gland manufacturers all you do is reverse the armour clamp ring to take account of the thinner material.

You might also try altering the carrier frequency to see if that has an effect. I had an issue sometime ago when the VFD was affecting a metal detector mounted below the drive.

Earthing should be at a central point. 24DC and everything else gets connected to this point.
Use a RF radiation meter to determine where the noise is coming from. It could be input (AC line) or output.
Check earthing to line filter. Is the filter designed for VFD's? If not, reverse it. IN goes to VFD. A standard line filter has all of it's filtering on the input side.