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Discussion Starter · #1 ·
I got the text for my next class in advance, so I don't yet have instruction in this, and I've never done it at work. In this picture, where would the neutrals be connected?



Sorry, I flipped the photo, but I don't think that will be reflected in the text.

Also, there is a section on closing a delta secondary. It says that prior to closing, a voltmeter on the open section should read 0V. I don't understand why this is. Also, if there is a mistake and it does not show that reading, how do you determine which coil is connected incorrectly? Thanks.
 

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Look at the wye configuration. What are your voltage to ground? It will be the same on all three (L1, L2, L3) what point is common to all lines?

On the Delta, could be corner ground or a 120/240 3 phase system.

On checking delta before closing. Must be lineman connecting pole pots or large individual transformers in a vault . Everything I have worked on is already connected. (3 Phase dry transformers)
This would verify if a winding was reversed before closing and starting a 4 of July fireworks show.

I was trying to get you to think about it some before handing you an answer.
 

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Look at the wye configuration. What are your voltage to ground? It will be the same on all three (L1, L2, L3) what point is common to all lines?

On the Delta, could be corner ground or a 120/240 3 phase system.
There is NO center tap for 120 VAC on the Delta Secondary

And no connection point per the drawing for a wye neutral on the primary.
 

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Discussion Starter · #5 · (Edited)
Yeah, I have seen wye connections with a neutral, but it wasn't shown here, so I didn't know. Where else might it go? I have seen deltas with a neutral center tapped on one of the coils, but the diagrams in this part of the book don't show that. They show deltas in which the voltage each phase and on the lines are all the same. Where does the neutral go in such a case?

Thanks, Randy. The way you structured your answer was better than spoon feeding me. Brian John seems to disagree with the content of your answer, but I'm waiting to hear from others.
 

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That is a wye/delta with the load being on the delta side. The wye side is the primary and typically you do not use a grounded conductor on the primary of a 3 phase transformer. The secondary of that transformer is not intended for other than phase to phase loads and there is no neutral.
 

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Yeah, I have seen wye connections with a neutral, but it wasn't shown here, so I didn't know. Where else might it go? I have seen deltas with a neutral center tapped on one of the coils, but the diagrams in this part of the book don't show that. They show deltas in which the voltage each phase and on the lines are all the same. Where does the neutral go in such a case?

Thanks, Randy. The way you structured your answer was better than spoon feeding me. Brian John seems to disagree with the content of your answer, but I'm waiting to hear from others.
Case closed, I am ALMOST always right.:laughing:
 

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Discussion Starter · #8 ·
don_resqcapt19 said:
That is a wye/delta with the load being on the delta side. The wye side is the primary and typically you do not use a grounded conductor on the primary of a 3 phase transformer. The secondary of that transformer is not intended for other than phase to phase loads and there is no neutral.
Thanks. Why are neutrals not used on these? I have only ever done doorbell transformers.
 

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I really think you should get enrolled in hands on courses, or in an apprenticeship. You would really enjoy the whole education, and hands on experience vs the bits and pieces of information you are getting on here. Some of the colleges have great classes as well. The classes I took have labs also.

Also, if you just got a job with a commercial contractor, or in a plant, you would learn a heck of a lot more than sitting on here.
 

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They are both right. It is however not a wiring diagram only an illustration to help you visualize the way these windings are connected.
 

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I was doing this on my phone. The pictures are the size of a postage stamp.
After I view a picture they disappear the next time I open the thread, just a gray box.
A Wye Delta setup is not that common in my opnion unless it may be used to feed A 240 volt machine from 208.

I did the opposite and fed a 3 phase 120/ 208 panel for a machine from 240 delta. Also 240 delta to 277/480 for another. Custom built by Square D, in the book but not on the shelf.

Back to your Delta. The drawing does not show a neutral, so it is ungrounded.
IF it was a 120/240 delta then there would be a connection by the letter 'B' for the neutral. The high leg would be above it.

IF the wye was an output then the neutral is in the center.

IF its for the input then NO neutral, just the 3 input lines.
 

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I


Back to your Delta. The drawing does not show a neutral, so it is ungrounded.
IF it was a 120/240 delta then there would be a connection by the letter 'B' for the neutral. The high leg would be above it.
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This transformer can still have a grounded secondary, a corner grounded Delta.
 

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So all the high-side phases are all H1, the neutral is H2, and all the low-side terminals are all dual labeled X1/X2.

Can't wait to see the guys apply their book-learning on the next transformer they get to wire. Apparently apprenticeship courses still leave a lot to be desired.
 

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Discussion Starter · #14 ·
dronai said:
I really think you should get enrolled in hands on courses, or in an apprenticeship. You would really enjoy the whole education, and hands on experience vs the bits and pieces of information you are getting on here. Some of the colleges have great classes as well. The classes I took have labs also. Also, if you just got a job with a commercial contractor, or in a plant, you would learn a heck of a lot more than sitting on here.
I'd love a job in a plant. I don't have experience in that kind of work, but I should start putting myself out there.
 

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Discussion Starter · #15 ·
Big John said:
So all the high-side phases are all H1, the neutral is H2, and all the low-side terminals are all dual labeled X1/X2. Can't wait to see the guys apply their book-learning on the next transformer they get to wire!
:D

Hey, would you mind telling me what the curly q lines are? I was told they are a handle to grab on to.
 

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So all the high-side phases are all H1, the neutral is H2, and all the low-side terminals are all dual labeled X1/X2.

Can't wait to see the guys apply their book-learning on the next transformer they get to wire. Apparently apprenticeship courses still leave a lot to be desired.
The illustration is showing three single phase transformers connected in wye or delta, not a 3 phase transformer. They connect them in school that way so the students actually make the wye and delta connections and they can see how the voltages add and interact.

To the OP, the open corner test shows that there is no potential between the last two points before you close the delta. If it's good, you see zero volts. If you read double phase voltage you've got one winding that is connected backwards.
 

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The illustration is showing three single phase transformers connected in wye or delta, not a 3 phase transformer. They connect them in school that way so the students actually make the wye and delta connections and they can see how the voltages add and interact....
Alright, I stand chastened, that's not a terrible idea.
 
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