# Delta-Delta Transformer Question



## testify (Sep 3, 2014)

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!


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## 460 Delta (May 9, 2018)

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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## testify (Sep 3, 2014)

460 Delta said:


> 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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## tmessner (Apr 1, 2013)

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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## testify (Sep 3, 2014)

tmessner said:


> 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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## joe-nwt (Mar 28, 2019)

Definitely a star point.


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## joe-nwt (Mar 28, 2019)

What are the 3 small wires at the bottom for?


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## tmessner (Apr 1, 2013)

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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## testify (Sep 3, 2014)

joe-nwt said:


> What are the 3 small wires at the bottom for?


They all go to the chassis under one lug


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## joe-nwt (Mar 28, 2019)

tmessner said:


> 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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## joe-nwt (Mar 28, 2019)

testify said:


> They all go to the chassis under one lug


 And where do the other ends go?


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## testify (Sep 3, 2014)

joe-nwt said:


> And where do the other ends go?


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?


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## tmessner (Apr 1, 2013)

underneath the bar is there anything tieing to the transformers


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## 460 Delta (May 9, 2018)

joe-nwt said:


> 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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## joe-nwt (Mar 28, 2019)

testify said:


> 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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## micromind (Aug 11, 2007)

460 Delta said:


> 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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## testify (Sep 3, 2014)

Thank you everyone for your help, I'll let you know Monday how she goes!


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