Phase or Nuetral ?

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romex jockey

romex jockey

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I'm having a rather hard time understanding the theory here,
this is SqD info for a corner grounded delta.....>

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What i don't understand is, are they providing a choice, phase OR neutral , or can they be both?

It would be enlightening if anyone's up on the code references that constitute this dif

thx

~RJ~
 
I do not understand your question. A corner grounded delta, using the NEC definitions, does not have a neutral. It has a grounded conductor and two ungrounded conductors.

As for why a two pole breaker is allowed for the 240V delta but a three pole breaker is required for the 480V delta, I assume that the difference is in the voltage withstand rating to ground in the design of the two pole breakers. The two pole breakers can handle 240V or more to ground, as would be seen in a 416Y/240 system or a 240/480 three wire single phase or a corner grounded 240 delta, but not the 480V to ground seen in a corner grounded delta.
The three pole breakers are designed for the higher voltage to ground found in a corner grounded delta at 480.

As for why the grounded conductor must be connected only to the center pole, it is possible that the center pole has a lower withstand voltage to ground than the outer two.
Hard to say for sure without knowing more about the configuration. But given that the NEC standard for the grounded conductor to be the B phase conductor, it is natural that this will automatically connect to the center pole in a fully loaded three phase panel.
 
GoldDigger said:
I do not understand your question. A corner grounded delta, using the NEC definitions, does not have a neutral. It has a grounded conductor and two ungrounded conductors.
Click to expand...

well that's the thing Gold one, I've always though of a 'grounded conductor' as a neutral.

So how do i treat this? Does one consider it a 'grounded phase' or 'neutral'?

Would i be doing anything different in the two setups posted above?

I see 240.22- 1 allows a grounded conductor through an OCPD, would it be colored white or orange? what about 3 ph fused disco's?

Is this all treated as an SDS?

Yes i'm confused....:(

~RJ~
 
romex jockey said:
So how do i treat this? Does one consider it a 'grounded phase' or 'neutral'?
Click to expand...
There's no real difference. To the supply system, it's grounded like a neutral.

To the load, it's a phase that just happens to have zero to-ground voltage.

I see 240.22- 1 allows a grounded conductor through an OCPD, would it be colored white or orange? what about 3 ph fused disco's?
Click to expand...
It would be colored white or gray, but can be supplied through a multi-pole breaker. It cannot be fused, because it could be the only line that opens.

If it passes through a fused switch, the fuse should be replaced by a non-fusible "dummy" or solid conductive bar.
 
You can ground any point of a source, once you do that becomes the "grounded conductor"

You can't ground more then one point - that results in undesired current flow, and if resistance is low enough between those points it will be at a high current level.

NEC as a general rule requires the neutral conductor when we have one to be the conductor that is grounded.

When there is no "neutral" as is the case with a single phase two wire system or three phase three wire delta you can ground any conductor you wish - then it is simply the "grounded conductor".

Used to be high leg delta systems weren't considered to have a "neutral" which made some sense, but then somewhat recently (2008 or 2011 maybe) NEC decided to define that grounded conductor of those systems to be included in the definitions of what is a neutral for application of NEC.
 
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