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Hello,

I am installing a repurposed 600V-208V 75kva delta-delta transformer that the client had in their shop. I am feeding a small panel for some general 120v receptacles. I understand that I can get 120v by tapping between 2 of the phases, but how do I see that in this transformer? Whoever had used this previously has this cable taped white which initially made me think that this was the neutral tap, but looking at where it is tapped it just seems like a ground to me? Can anyone offer me any assistance? Thanks!

152059
 

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Ready Mix concrete plant electrician
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That’s a 208 star, not a 208 delta, the neutral-center point of the connection should be grounded. A 208 delta would be a real rare item.
You will see 120 vac from blue black and red to the white neutral.
Pet peeve time here, set the tap so you have 208 vac at the secondary and not 220 or 200, rant off.
 

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Discussion Starter #3
That’s a 208 star, not a 208 delta, the neutral-center point of the connection should be grounded. A 208 delta would be a real rare item.
You will see 120 vac from blue black and red to the white neutral.
Pet peeve time here, set the tap so you have 208 vac at the secondary and not 220 or 200, rant off.
Oh sweet, thanks!

Weird how the side of the unit just says 208, where other wyes I've seen say 120/208

Appreciate your time
 

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That may be a 208 only output with no neutral. If so you will not get 120 out of it. What does the schematic show on the nameplate?
 

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That may be a 208 only output with no neutral. If so you will not get 120 out of it. What does the schematic show on the nameplate?
No schematic. She is an old gal they pulled off a shelf. It would be a cruel joke for someone to play by taping that wire white and having a 4 conductor secondary if that wasn't a neutral, don't you think?
 

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Definitely a star point.
 
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What are the 3 small wires at the bottom for?
 

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I am suspicious of that label saying 208v, not 208/120v. Does the grd/neutral bar have a connection to the bottom of the transformers?
 

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I am suspicious of that label saying 208v, not 208/120v. Does the grd/neutral bar have a connection to the bottom of the transformers?
Yes, the three bolts, left, right and center.
 

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What are the 3 small wires at the bottom for?
Looks like they are landed on the bolts that tie the coil tabs to the neutral bus, then bonded to the case. Seems kinda odd to do that, but the CEC may call for that.
 

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Looks like they all go to that lug at the bottom which would be my neutral point :)

Why do you suppose the fellow/gal before attached right to the ground bar?
I would have gone to the neutral bar with the ground as well. But I would have removed the small wires. There is already a bond strap installed so someone must have added the small wires in after. What for I can't say.
 

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Looks like they are landed on the bolts that tie the coil tabs to the neutral bus, then bonded to the case. Seems kinda odd to do that, but the CEC may call for that.
That's what I see too.

You can see the ends of the coil stabs under the copper busbar.

Since one end of all 3 coils is connected together, this is a Y connection and the busbar is the neutral.

If it were a 3 wire ∆, each coil would be connected to another coil in a sort of series connection.

If it were a 120/240 ∆ one coil would have 3 stabs, the other 2 would have 2. The neutral would be connected to one of the 3 stabs.
 
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