Going from delta to wye?

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georgestolz said:
Can you elaborate? I've never seen an "X" as a seperator. What does it mean?
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The slash (/) means that both voltages are available. The cross (X) means that either voltage is available. Notice on a standard transformer the primary is often listed as 240X480 which means you can wire it for either 240V input or 480V. The transformer secondary is listed as 120/240 which means it can supply 120V and 240V at the same time.

What is the significance of the location of the "Y"?
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It defines the connection of the transfomer windings. I apologize that I can't remember all of the options other than a standard 4 wire connection like 208Y/120.

What is a zig-zag transformer?
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This is a special autotransformer connection used to effectively turn a 3 wire delta system into a 4 wire wye. This is not 100% accurate but it explains the concept.

My apologies for offending your delicate sensibilities, I have miswritten nominal voltages in the past as well.
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I don't know if I am supposed to answer this one, but. I too have been miswritten electrical terms and as a result have been able to strecth many topics into mega-length discussions. One of my personal improvements goals is to be more correct in my term usage even if it is at the expense of appearing pompus at times.
 
For years I wrote 208/120 (not sure why, I think it came from my business partner) anyway last year I had an engineer trash a load survey I did using this nomenclature and I had to redo the report (easy enough). You'd have thought I slapped him for the lecture the contractor told me he received (I never met any was only on a 3 way phone conversation with him. This was not the only issue he had with my report but it was major to him...Need to check my standards next time.
 
I'd say the way the subject has turned is definutely relevant to the OP, but we're not applying what we're saying to what Vern is saying. I'm gonna try.

Terminology is key to the discussion, because I think Vern is saying things that mean things other than what he intended.

VernB said:
I've confirmed from visual inspection of the POCO transformers, this is definitely delta, not wye. There's only 3 phase conductors in the drop from the pole, no neutral.
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(Coloring mine)

Vern, if you're saying that the sentence in blue is the basis for the conclusion in red, then you're not saying what you intend to say.

The sentence in blue is saying that this is an ungrounded system. An ungrounded system can be delta or wye, physically speaking.

VernB said:
Yup, this is an old mill, all the original equipment was 208 3P and the lighting was all fluorescent with 220V ballasts so they never had any provision for anything else except 208V in the older areas of the building. Loads will be standard 120V.
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I'm thinking what you intended to say is that the ballasts were all wired "Line-to-Line" at 208V. Is that correct?

Basically, I think you are dealing with a 208V ungrounded wye system.
 
VernB said:
On the entrance in question, there's only 3 conductors in the drop and there is no common connection among the 3 transformers, so I'm sure it's a delta configuration.
Vern
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George, did you see the above? If you can see the pole pigs, you can often identify wye and delta connections.

Vern, my bias is similar to George's; I also expect that the service is really from a wye bank but with no neutral supplied. The 'common' interconnection between the transformers can be 'hidden', via what looks like the 'grounding' terminal on the can.

Can you see the primary bushings on the cans? One or two primary bushing per can? Is the primary connected wye or delta?

-Jon
 
While off on the topic of voltage and system designation. (Which is the way I was always taught them - Voltage to ground/system voltage.) What is 220? And where does it come from? And why wont it go away!?!? :grin:
 
e57 said:
While off on the topic of voltage and system designation. (Which is the way I was always taught them - Voltage to ground/system voltage.) What is 220? And where does it come from? And why wont it go away!?!?
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In the early days of electrifying the US the nominal supply voltages were 110, 220, 440V. During the '40s-50's these were moved up to 115, 230, 460V. By the mid 60s they reached their present and official (as listed in the NEC) of 120, 240, 480V.

Why they won't go away is purely due to bad habits. I have no problem with three phase voltage systems but when it comes to residential I tend to slip into the "220" world. In fact this bad habit caused me to get an answer wrong on a test back in 1975. I can't forget the test but I also can't break the habit.
 
VernB said:
Al, that's a confirm, 120V for most of it and anything that needs 240 will be just fine with 208.
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Vern,

I think you need to look at just having the service "upgraded" to 208Y/120, 3?, 4W. Currently it sounds as though you have a 208V, 3?, 3W service (it doesn't matter whether it is delta or wye as loads do not "know" the difference). To consider using sub-transformers is just "dancing" around the problem.



Question for others on nomenclature:
Is the term "open wye" a technically correct terminology by IEEE standards? It seems to me wye transformation is open by its very nature. So "open wye" is a nothing more than a redundancy. If it is a legit term, would someone please supply the "legit" definition?
 
georgestolz said:
(Coloring mine)

Vern, if you're saying that the sentence in blue is the basis for the conclusion in red, then you're not saying what you intend to say.

The sentence in blue is saying that this is an ungrounded system. An ungrounded system can be delta or wye, physically speaking.


I'm thinking what you intended to say is that the ballasts were all wired "Line-to-Line" at 208V. Is that correct?

Basically, I think you are dealing with a 208V ungrounded wye system.
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Correct, the ballasts are all wired line to line for 208V. I've actually spoken to some former employees of the mill when it was operating as a mill and confirmed the delta configuration. Of course, I'm looking at the POCO transformers from the ground, but as far as I can see, it's definitely delta. I'll try to get a cell phone pic when I go back in tomorrow.

Vern
 
winnie said:
George, did you see the above? If you can see the pole pigs, you can often identify wye and delta connections.

Vern, my bias is similar to George's; I also expect that the service is really from a wye bank but with no neutral supplied. The 'common' interconnection between the transformers can be 'hidden', via what looks like the 'grounding' terminal on the can.

Can you see the primary bushings on the cans? One or two primary bushing per can? Is the primary connected wye or delta?

-Jon
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Jon, I'll try to get a couple of pics with the cell phone tomorrow when I go back, I've confirmed with former employees of the mill that these entrances were definitely delta and what a pain they were to deal with because they were very unusual and most of the electricians didn't understand them. Gives me a lot of confidence having to deal with them now :).

Vern
 
Smart $ said:
Vern,

I think you need to look at just having the service "upgraded" to 208Y/120, 3?, 4W. Currently it sounds as though you have a 208V, 3?, 3W service (it doesn't matter whether it is delta or wye as loads do not "know" the difference). To consider using sub-transformers is just "dancing" around the problem.
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That of course would be the optimal fix, that's for sure, there's a few roadblocks to it. First is that nobody really wants to disturb the working service because nobody's really comfortable messing with it. Second problem is opening up a can of worms with local code enforcement by having to rebuild/replace existing grandfathered facilities up to "modern". As it is, local AHJ is leaning on them to rip out all of the aerial power and replace it with pad mounted transformer and centralized meters. Lovely idea, but it means major disruptions to the building operations and the cost of it would be phenomenal.

For better or for worse, I'm stuck dealing with what I've got in place (isn't that the way it usually works?).

Vern
 
e57 said:
Is this the "210-220 - whatever it takes" quote that is often heard? I have no memory of the movie....
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Yep:

"Are you gonna make it all 220?" - Martin Mull

"Yeah. 220... 221, whatever it takes." - Michael Keaton
 
Smart $ said:
Is the term "open wye" a technically correct terminology by IEEE standards?
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An open wye transformer bank has two transformers.

The classic application for an open wye exists when the PoCo, for whatever reason, only has two of three primary conductors (phases) coming to the transformer bank, and the PoCo wishes to supply 3 ? to a customer.

The PoCo will put two transformers on the pole and connect the primary windings in an open wye. The third wye connected primary winding is not there.

The secondary windings of the two transformers will be hooked up in the classic open delta. The customer will receive, typically, 120 / 240 V , 4 wire 3 ? with a wild leg.
 
VernB said:
Correct, the ballasts are all wired line to line for 208V. I've actually spoken to some former employees of the mill when it was operating as a mill and confirmed the delta configuration. Of course, I'm looking at the POCO transformers from the ground, but as far as I can see, it's definitely delta. I'll try to get a cell phone pic when I go back in tomorrow.

Vern
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I'm back on site, I've measured the voltages as 245/248/250 between phase conductors and 132/142/157 from each phase to ground. At this point, I'm guessing that this is properly 240D, not the 208 that it's marked as.

Vern
 
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