Grounding v/s Sheilding

[Bering C Sparky]

Hi Guys,
Not really sure I get your point, I think we have one of those cant see the Forest because all the Trees are in the way scenarios going here.

So lets recap:

My post was about using a cable that has a SHEILD surounding a conductor. (Only a shield, not a seperate shield and a seperate ground wire) The cable assembly is listed as having only a shield in the spec sheet, no where does it mention anything about Ground/PE/Earth condutor.

QUOTE FROM SPEC:
"OLFLEX FD 90 CY with tinned copper braid SHIELDING is used for applications where EMI emissions need to be suppressed"

I have an engineer telling me that it is ok to use this SHIELDING as a ground conductor. (Nowhere in my cable spec does it say that this SHIELDING is meant as or rated for this purpose.)

I think this is pretty cut and dry and no one can say otherwise. Would you not aggree?

Then you post the Draka cable MCMK. This cable has the GROUND conductor spread around the outer circumference of the cable assembly.

So now we know that Draka's GROUND conductor configuration is unlike most other cables. They have it wrapped around the votage conductors instead of being a seperate single conductor the way we normally see the GROUND conductor in other cable assemblies.
Thats fine it is still a GROUND conductor, it is approved and listed as such, as PE, it says so right in the spec for the cable.

However no where for the MCMK cable assembly does it say anything about this cable being compatable for the suppression of EMI. (I have looked and I see nothing, if it is there please point it out)

Then you post another cable that is supposedly proving your point that the shieling on a cable assembly can be used as a ground conductor.

I dont see it that way, BECAUSE the MCCMK cable assembly you posted now has a seperate foil SHIELDING that is used to suppress EMI and a seperate GROUND conductor that just so happens to be wrapped around the foil shield, only because this is the configuration Draka has chosen for there GROUND conductor.
Here is the link to Prysmian Group that you keep refering to.

http://www.drakakeila.ee/index.php?group_id=29&page=69&

I do see a few cables on here that are rated as Electro Magnetic Compatible Cables, as is the MCCMK cable you referance. The MCMK that you first posted says nothing about being Electro Magnetic Compatible. (This is because it is missing the seperate foil SHIELD)

Whats your point?
All cable manufactures offer cables that are Elecro Magnetic Compatiable.
They are called SHIELDED cables.
They have a SHIELD that is used for the suppression of EMI and they have a SEPERATE GROUND conductor for grounding the equipment and as a path for fault currents.
The MCCMK cable you show is no different than any of the other cable manufactures SHIELDED cables. It has a seperate foil SHIELD and a seperate GROUND conductor.

The only differance is Draka has chosen to configure there GROUND conductor in the cable assembly different from most cable manufacturers.

I think this is obvious, as you can see Draka has the same GROUND conductor configuration in there NON-SHIELDED cables as they do in thier SHIELDED cable assemblys.

I see the forest quite well, the trees are the forest. Take a few steps back and have a good look, can you see the forest?

Dont know about you but I am bored with the subject.
Dont get me wrong, I enjoy the back and forth exchange of ideas and difference of opinions, its what keeps us sharp and most times I learn a thing or two from it.
But we have whipped this poor horse to death, and I think we should put it out to pasture.

Have a great day and look forward to chatting with you around the forum. (Only in another thread on another subject)

Best Regards,
BCS

 

[TurpoUrpo]

It was fully theoretical discussion until you posted cabletype you are supposed to be using. Understand we dont have crystall ball to look at ur spec in?

My point was, that it is possible to have shield + pe wrapped around as one. If you read that spec sheet again. It states "PE = copper foil and concentric layer of copper wires". It does not state shield = copper foil and PE = concentric layer of copper wires.

ps. writing long wall of text and bailing out is just stupid.

 

[seppoalanen]

This is off the topic a little bit, but:

The main thing is correct motor cabling from VFD, I think.
Use Symmetric cable. Connect shield (and/or 3 symmetric PE-wires) only in motor and VFD's "PE", not anywhere else metal construction inside the cubicles etc. Symmetric cable "sucks" harmonics to VFD's DC-circuit.

2´nd note is that 2 small parallel cables is better than one big. Reason is that inductive reactance is 1/2 with same gross section sum.
Nothing to do with small cables but it means more with great ones.
Inductive reactance depends of the distance between phase wires, so 1-core cables enlarges it.

3'rd note, allways Voltage loss is not the main thing. Enough of Torque is the main thing.

 

[Bering C Sparky]

I gave my spec in the very first post. #1

(We are using Lapp FD90CY single conductor cables run in parallel)

and i gave the internet link in post #3

http://products.lappgroup.com/online...-fd-90-cy.html

No "Crystal Ball" Required (Perhaps a new prescription on reading glasses)

My point was, that it is possible to have shield + pe wrapped around as one. If you read that spec sheet again. It states "PE = copper foil and concentric layer of copper wires". It does not state shield = copper foil and PE = concentric layer of copper wires.

The entire "Point" of this tread was that using intended and listed SHIELD as a ground is not correct.

ps. writing long wall of text and bailing out is just stupid

Well that is your opinion I guess. (And we all know what they say about opinions!!)

I am not the only person reading this, it had well over 800 views last time I looked.
If I am the one that is out of line or just plain bonkers about anything I have said, then I would not mind if someone whos opinion holds some credibility pointed out that fact to me, so I can go back and re-read this tread and see the error of my ways.

The only 2 things I find "stupid" about all of this would be:

1) Having to over explain myself by writing a long wall of text, to try and make someone who did not even READ the tread correctly and grasp its content, understand what I am saying.

2) Continuing with this mindless discussion.

Smile

Grab a cold one
and let it go, life is to short.

BCS / OUT

 

[TurpoUrpo]

Well, i did not read you post #3 after you had edited it seems. I dont read multiple times from the beginning.

 

[Bering C Sparky]

Mr. Urpo,

Good day to you sir,
I should just let it go as I advised you to do yesterday, but since you chose to respond again lets break down your last responce with a few facts, because again or rather still I dont see your point.

1) Post 3 was submited at:

August 1st, 2014, 04:34 PM

2) My edit was made at:

Last edited by Bering C Sparky; August 1st, 2014 at 04:43 PM.

So in that 9 minute window you read my post before the edit was made? Ok that could happen we will give you that one. Still does not change that the cable type was given in post #1.

3) The very next post #4 from iant just 26 min after my post and 15 min after my edit

August 1st, 2014, 04:58 PM

iant said

Thanks for the link - I had already googled it

4) In post # 18 I say

I am ordering 20,000 feet of the stuff I posted the other day!

5) We did not hear a peep from you until

August 5th, 2014, 07:36 AM

So agian what is your point?
It seems you are saying that you missed it in the first post, read the third before I edited it 9 min later, did not pick up on the fact in post 4 or again in post 18, so this is your justification to the fact you keep running off about something with no relivance.

If this is your point, OK I forgive you, you did not know, you missed it numerous times, and still feel the need to justify yourself insead of just cutting your losses and moving on, as I have advised at least twice.

I am willing to live and let live and compleatly overlook the fact that you were the one that implied that I was "stupid".

At last look there were 969 views to this thread, and it would seem you are the only one that had trouble following it.

My wife often tells me that I should have been a lawyer instead of an Electrician, because I thrive on and live for debate and have an eye for presenting my case.
Every thing I have said here is a fact, thats the beauty of the written word, you can go back and read it again and the facts are there for all so see.

I thought the verbal spanking you got yesterday was more than sufficient, but obviously it was not, I pray:wish: that your second helping today has satisfied your hunger for more.

I dont think you had that cold one yesterday, did you????
Go get a cold one you will feel better, have two or three.
I promise it will make you feel better.



Have a wonderful day and please let it go this time.

BCS

BCS