Don't trust what you see

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roger

roger

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If you see something in print or in cyberspace be sure to question it before you count it as gospel.

Here are two examples, one is wrong, and one is just not complete, both deal with transformers.

#1 Not complete, this is drawn not showing voltage between A & B or A & C. They meant to show this but left out some arrow points. Wouldn't you think they could do better proof reading.

fig1-4.gif

coutesy of http://www.elec-toolbox.com

#2 Not throwing stones but the notes to the delta diagrams below are not correct.

neutral-1.jpg


Diagram courtesy of http://www.grafixbynix.com/
and www.joetedesco.com


Roger

[ September 01, 2003, 12:03 PM: Message edited by: roger ]
 
Re: Don't trust what you see

Roger,
I understand your point, but the code does yet now have a definition of neutral. If the panel action on proposal 1-122 stands, the grounded conductors on the detla systems in the drawings will not be neutrals.
Neutral Conductor. A conductor, other than a grounding conductor, that is connected to the common point of a wye connection in a polyphase system or the point of a symmetrical system which is normally at zero voltage.
Click to expand...
The 120/240 volt 3 phase 4 wire delta system is not a symmetrical system.
Don
 
Re: Don't trust what you see

The only phases associated with the star point as a current carrying source is A and C phase. B phase is not in the equation. A and C phase are balanced (symmetrical) in relation to the star point.

I hope the code people leave this alone. This is a definition for the IEEE/NEMA.

The scope of the NEC is not for determining technical accuracy. It is only to utilize the definition.
 
Re: Don't trust what you see

What is the deal of not posting the drawings. These same schematics were made before I was born. I don't think anyone has a personal claim for their use.
 
Re: Don't trust what you see

Joe, I E-mailed Elec-toolbox on the top diagram some time ago and they obviously aren't concerned in making any corrections.


Roger

[ September 01, 2003, 02:38 PM: Message edited by: roger ]
 
Re: Don't trust what you see

Roger: My compliments for exposing this error. Any tradesman who notices an error in technical drawings is unethical and irresponsible if he doesn't make it known.

[ August 31, 2003, 04:08 PM: Message edited by: bennie ]
 
Re: Don't trust what you see

Roger:

The subject of the neutral letter and the diagram was reposted above:

You are correct, and I am sorry for making a big deal out of it, I only want to see a courtesty paid to my webmaster when the images from our site are used.

http://www.grafixbynix.com/

:)

[ September 01, 2003, 11:33 AM: Message edited by: joe tedesco ]
 
Re: Don't trust what you see

Joe, thank you for reposting the diagrams.

I will (and normally do) give credit when I post from others sites, or use others materials.

I appologize Dave.


Roger

[ September 01, 2003, 11:57 AM: Message edited by: roger ]
 
Re: Don't trust what you see

Roger: I don't go to any other site. I am curious about who is the author of these drawings and statements. Email to me.
 
Re: Don't trust what you see

Bennie, I e-mailed a PDF file to you.

Roger
 
Re: Don't trust what you see

Has this been adopted by the IEEE as a Standard? I sure hope not, it is technically wrong.

There is nothing that needs changing when applied to a neutral conductor.

Neutral is not a thing, it is describing a thing.

There is 14,500,000 words in the English language. We don't need a new spin on something that does not exist as a sole item.

This is the best forum to discuss this issue, there is more interest here. I get a lot of private email to prove the fact.
 
Re: Don't trust what you see

Roger

Just got back from a short trip, I would have liked to have seen that second drawing on the delta transformer. I have found a couple of errors in the 2002 handbook graphics but still a great book.

The above sentence about errors was changed.

Ronald :)

[ September 01, 2003, 10:59 AM: Message edited by: ronaldrc ]
 
Re: Don't trust what you see

Hi Joe thanks for reinstalling the picture.

Now my 2 cents worth.

I agree with the author of the picture.Technically C and D are not neutrals.

But X0 would function as a neutral from X1 to X3.

I agree the neutral is a technical term and not a piece of gear.

Ronald :)
 
Re: Don't trust what you see

Ronald: You have a good point. I regard the center tap winding as a separate single phase system, the center tap is half and half between A and C phase. B phase is not used for this system.

A,B, and C phase make a three phase system that does not use the center tap neutral conductor.

The single phase, and three phase components are two different sources.
 
Re: Don't trust what you see

The grounded conductors in diagrams (C) & (D) are as much neutrals as the grounded conductor in diagram (B).

Let's forget attempts at a blanket definition and look at the conductor only.

Let's give all the winding ends a value of 10 amps of load at "center to end of winding voltage".

In diagram (A) the HOT and GROUNDED CONDUCTOR would both see 10 amps and would be necessary to complete the circuit

In diagram (B) the HOTS at X1 and X2 would see 10 amps each and the GROUNDED CONDUCTOR would be at zero and could be removed not effecting the circuit.

In diagram (C) and (D) the HOTS at X1 and X3 would see 10 amps each (we are not concerned with any loads beyond this winding) and the GROUNDED CONDUCTOR would be at zero and could be removed not effecting the circuit.

In diagrams (B),(C), and (D) the GROUNDED CONDUCTOR is NEUTRAL in the operation of the loads.

Roger

[ September 01, 2003, 03:13 PM: Message edited by: roger ]
 
Re: Don't trust what you see

I agree Roger. I am disgusted that engineers are even addressing this issue. Surely they have better things to do. I hope the code panel members deal with more important topics.

As long as the wire is white, it qualifies as a neutral conductor, merely by the color.
 
Re: Don't trust what you see

Roger,

No apology necessary!

Thank you for posting your latest explanations concerning the drawings. Transformer theory is always in need of a refresher for all of us that don't think about them on a regular basis.

Thanks,
Dave
 
Re: Don't trust what you see

Rogger,
I agree that the grounded conductor for the 3 phase 4 wire delta systems should be called a neutral. However it is my opinion that under the accepted proposal for a definition of a neutral conductor, it will not meet the definition. The definition requires that the system voltage be symmetrical and with a high leg, the system voltage is not symmetrical. Yes, the voltage between the 2 conductors that are used with the grounded conductor is symmetrical, but the "system" voltage is not. Maybe comments are needed on this proposal (1-122).
Don
 
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