# Delta? wye?



## telsa (May 22, 2015)

4160VAC to 480Y277VAC transformers are very common.

4160VAC to 480VAC delta is uncommon. 

The place to look would be right on the transformer body.


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## brian john (Mar 11, 2007)

Sblk55 said:


> Hi all, I have been a maintenance electrician in the same small plant for 25 years. I have never needed to know so never asked, but how do you know if your system is Delta or Wye?
> 
> We get 4160 from PoCo and transform it to 480 to feed our buss system. The buss system is three wire, no neutral. It is a grounded system.
> 
> ...


What is the voltage to ground 480 VAC on 2 phases or 277 VAC on all phases?

Or what is grounded.


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## joebanana (Dec 21, 2010)

All depends on where it's grounded. Corner, or center.


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## Sblk55 (Sep 8, 2017)

We run a bit high, phase to phase is 493, phase to ground is 285.

Steve


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## Sblk55 (Sep 8, 2017)

A few years back we had a large project where we had an outside contractor do the work. They wanted to do the lighting on 277 and had to set a small 50KVA transformer to create a neutral. 

Steve


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## NewElect85 (Dec 24, 2017)

telsa said:


> 4160VAC to 480Y277VAC transformers are very common.
> 
> 4160VAC to 480VAC delta is uncommon.
> 
> The place to look would be right on the transformer body.


Lol.
Like my dad says;

One word:

Cast Core :biggrin:


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## brian john (Mar 11, 2007)

telsa said:


> 4160VAC to 480Y277VAC transformers are very common.
> 
> 4160VAC to 480VAC delta is uncommon.
> 
> The place to look would be right on the transformer body.


In your area.


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## brian john (Mar 11, 2007)

Sblk55 said:


> We run a bit high, phase to phase is 493, phase to ground is 285.
> 
> Steve


 I would think based on the above you have a 3 phase 4-wire grounded wye with a 3 phase 3-wire bus.


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## Sblk55 (Sep 8, 2017)

Thanks to you all and I will definitely check the transformers on Tues.

Steve


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## micromind (Aug 11, 2007)

Sblk55 said:


> A few years back we had a large project where we had an outside contractor do the work. They wanted to do the lighting on 277 and had to set a small 50KVA transformer to create a neutral.
> 
> Steve


Most likely, the original system is a 480 ungrounded ∆. Or possibly a 480 grounded B system. 

The transformer is just a basic transformer with a 480∆ primary and a 277/480 Y connected secondary. 

Then 4160 transformer is most likely not 277/480 but rather, 480∆. 

One nice thing about a closed ∆ is that it tends to balance voltage at the expense of current. Motors like balanced voltages.......


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## Sblk55 (Sep 8, 2017)

Thanks Micromind, you are correct 20 years ago it was ungrounded. when we changed from 500 KVA transformers to 750 KVA they grounded the system. When pulling out one of the feeds to one of the busses they found where one phase had been shorting to the conduit. With no ground it never triped the breaker. They decided it would be safer to have a ground so that would not happen again.

Steve


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