PE and/or functional earth 2

[Skogsgurra]

EN 50178 (VDE 0160) says that Protective Earth and Functional Earth are sometimes needed in frequency inverter installations. We usually only connect the PE - and it does work quite well. What it does to EMI is probably not so nice, however.

Are there any rules-of-thumb telling when this would be necessary? Or does contemporary legislation say that both must be connected, end-of-discussion? Any references? Any practical experience out there?

 

[jbartos]

Suggestion: Visit

http://www.601help.com/Disclaimer/glossary.html

for:
Definitions

http://honeywell.silverw.com/docs/61-86-25-09.pdf

see page 4 for symbols and Honeywell instructions
etc. for more info

 

[Skogsgurra]

jb,

Why did you point me to these randomly chosen references?

They do not even say anything about frequency inverters and functional earth. Yes, the glossary contains those words, and shows up when you do a google, but that is something that I do before I put a question on eng-tips and glossaries do not say anything about legislation or rules-of-thumb, which I asked for.

It would be extremely good if you tried to understand that most of us also understand how google and similar search engines work - so you do not have to do the googling for us.

I hope for answers from people that truly understand the question - I do not need answers from robots.

 

[skiier]

skogsgurra:

I always like the discussion of PE vs FE. I am not an engineer but I am Technologist/Electrician with a few years working experience. I have installed many a VFD system and have always connected to PE. The whole topic drives me crazy because in practical experience I have always found that PE and FE end up the same point electrically anyway. I will get corrected by everyone here on this point but in practical terms this is a true point. I have never seen a "perfect" installation - you know the fairy tale land where PE and FE are isolated and all their appropriate gnd bonds and sheilds go to the right points. Ya right. The systems always ends up shorted by the construction method or misplaced bond or sheild or carelessness or lack of experience or whatever. You get the idea.
I am not going to point you at some "links" like jbartos but I can tell you this. Give them what they want! Gnd the hell out of everything according to manufacturer's specs or any other spec you like. Please the over designing masses trying to cover their asses and forget about it.
Because no matter how hard u try I'll lay odds that any PE/FE system u come across will be not as designed - I mean the same point electrically for PE and FE.
The discussion of PE vs FE is like the "song that never ends" . Hehehe. I am probably not helpful either to you. But I just wanted you to know what u r up against.
Mother nature will ultimately find a path to gnd for whatever it imposes upon it so why give it a choice with 2 paths?. Give it 1 path and will use that path.
skiier

 

[Skogsgurra]

skiier,

Perhaps I played too much of an innocent newbie in my question. I agree with you, completely. And the fact that no one has pointed to any useful links goes to prove that there might not be any "rules of thumb" or "best practises" out there.

I could disagree in one point; the PE and FE do not necessarily get in touch before they reach mother Earth, but I agree that they mostly do. Anyhow, both usually get polluted by HF currents from inverters and such things so none of them can be used to connect shields to either.

Yes, "the song never ends" but singing it out loud can help some understand the problem - and perhaps get closer to a workable solution.

I like your point "give them what they want and ground the hell out of of everything". What you end up with if you do that is a ground plane, more or less distributed, but a ground plane nonetheless. And that is always a good thing.

 

[jbartos]

Comment on skogsgurra (Electrical) Jan 20, 2004 marked ///\\jb,
Why did you point me to these randomly chosen references?
///There have not been posted specifications in the original posting to the Forum volunteers what is exactly expected. How can one know what is exactly requested?\\They do not even say anything about frequency inverters and functional earth.
///Actually, they elucidate the very essential for larger number of their customers and clients what these are in terms of symbols and definitions. To some extent, the grounding principles do overlap from device to device or product to product. Electrical safety code may refer to a product category grounding safety without spelling out specific product.\\ Yes, the glossary contains those words, and shows up when you do a google, but that is something that I do before I put a question on eng-tips and glossaries do not say anything about legislation or rules-of-thumb, which I asked for.
///Actually, the manufacturer has more available if requested. Have followed up on that link?\\It would be extremely good if you tried to understand that most of us also understand how google and similar search engines work - so you do not have to do the googling for us.
///I disagree. In many instances, the internet search is very dependent on a proper background in the area and proper vocabulary. I received many positive responses within my 7000 + posting in this Forum.\\I hope for answers from people that truly understand the question - I do not need answers from robots.
///It speaks for itself. """Any references? Any practical experience out there?"""\\\