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Discussion Starter · #1 · (Edited)
Me and my Journeyman are installing a 45kva transformer and he is letting me hook it up. While doing so I noticed that H1 is connected to the 480v tap on the first coil (via a 10awg wire) but the actual bus goes into the second/middle coil. Which one determines the H1 label? Is it the tap 10awg wire or the bus that goes into the coil?

Also, the bus that is labeled X2 is going into the same coil that the H1 bus is entering. I'm sure it's all right I would just like to understand how it works. Thanks
 

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Donuts > Fried Eggs
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...I noticed that H1 is connected to the 480v tap on the first coil (via a 10awg wire) but the actual bus goes into the second/middle coil. Which one determines the H1 label...?
Neither, H1 refers to the connection not the winding. So that spot where the tap lead from one winding joins the bus lead from another winding is H1.

A clearer example might be X0: There's no such thing as a "neutral winding" in a transformer, but every wye has an X0 because that's the common connection between all the phase windings.
...Also, the bus that is labeled X2 is going into the same coil that the H1 bus is entering...
The H and X coils for each phase are wound around each other on a common iron core, but they are not actually electrically connected. Think of them each as a stand-alone 1Ø transformer.
 

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Discussion Starter · #5 · (Edited)
Thanks! So the solid metal that goes from the bus into the windings is what exactly? Are the 10awg wires doing nothing but giving voltage to the proper windings?

On the middle coil where the x2 h1 bus are would you hook it up red, brown and so forth on the others and rotation would be clockwise? Is there a way to check everything if the labels were not there? Like rotation and proper terminations? I'm sorry if this is not worded great but thanks for all your help
 

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Bilge Rat
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Each of the 3 coils actually has 2 coils, a 480 volt and a 120 volt.

Dealing with the 480 ones first and using the center one as an example, H3 is connected to one end of the 480 coil.

The other 'end' of the coil is actually those things that the wire is connected to. They are called taps. Notice how each tao is further down the winding of the coil. This will effect the turns ratio and yield a different voltage on the 120 coil depending on which tap is selected.

Note.....all taps MUST be in the same position, otherwise you'll have imbalanced voltages. Bad news.....

Note that the H end of each coil is connected to one phase of the 480. The other end (the tap end) is connected to a different phase. That's how 480 is applied to each coil.

This configuration is called a delta, because a drawing of it looks like a delta triangle. It uses all 3 phases, but not the neutral.

Now for the 120 coils.

These are the X coils. One end of all 3 of these coils is connected to XO. The other end is connected to one of the X terminals (X1, X2, X3). This connection is called a wye, because when it's drawn it looks like the letter Y.

If connected per drawing, the phase rotation will be the same one the 120 side as it is on the 480 side. The transformer doesn't care what rotation it is, it simply supplies the same on both sides.
 
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