# Neutral required to transformer?



## RIVETER (Sep 26, 2009)

Honestly said:


> I am feeding a 480 delta- 208/120 wye transformer from a 480 wye source. Is there a code article that would require a neutral to be pulled with the phase conductors to the transformer?


That I remember I never did. Your 3 phase 480 volt is the feed and on the secondary you DERIVE your neutral, if needed to the load.


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## FrunkSlammer (Aug 31, 2013)

Where would you put it?


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## RIVETER (Sep 26, 2009)

FrunkSlammer said:


> Where would you put it?


If you are talking to me it would originate at the X0 lug of the transformer.


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## Honestly (Feb 3, 2011)

I did not think the transformer needed it, but thought I might be missing a code requirement to pull it. I understand that I will be deriving a neutral on the transformer.


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## kbsparky (Sep 20, 2007)

No neutral on the primary side.

Yes neutral on the secondary side.


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## brian john (Mar 11, 2007)

kbsparky said:


> No neutral on the primary side.
> 
> Yes neutral on the secondary side.


As long as it is a delta wye which I would think 99% of transformers in a commercial establishments (excluding buck boost).


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## chicken steve (Mar 22, 2011)

The funny thing is, it's the norm for us to derive a noodle, where the poco's will often run a solid noodle thru to us .....~CS~


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## BBQ (Nov 16, 2010)

Honestly said:


> I did not think the transformer needed it, but thought I might be missing a code requirement to pull it. I understand that I will be deriving a neutral on the transformer.


A delta - wye transformer will not need a neutral on the supply and only needs a neutral on the load side if you want to.

A wye - wye transformer would require a neutral on the supply side and only needs a neutral on the load side if you want to.


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## Honestly (Feb 3, 2011)

BBQ said:


> A delta - wye transformer will not need a neutral on the supply and only needs a neutral on the load side if you want to. A wye - wye transformer would require a neutral on the supply side and only needs a neutral on the load side if you want to.


No problem feeding 480 delta transformer from 480 wye service- correct?


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## Honestly (Feb 3, 2011)

Which begs the question, when would a wye primary transformer be required?


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## ScooterMcGavin (Jan 24, 2011)

Honestly said:


> Which begs the question, when would a wye primary transformer be required?


Why wye? Wye primaries are often used on large substation class transformers. 1 reason is the closer you get to the star point the lower your voltage is to ground therefore requiring less insulation and the windings can be closer to the transformer can. Another reason is that by having the neutral it gives you more options for your protective relaying of the transformer. Wyes also handle unbalanced loads better which for all these reasons that pretty much all utility generators are wye connected.


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## Big John (May 23, 2010)

Honestly said:


> Which begs the question, when would a wye primary transformer be required?


 There's no requirement. The only time I've seen it at less than 600V is when someone is reverse feeding a ΔY transformer to use it as a step-up, in which case you just float the wye.


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## di11igaf (Jan 1, 2012)

Honestly said:


> No problem feeding 480 delta transformer from 480 wye service- correct?


No problem at all.


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## Vintage Sounds (Oct 23, 2009)

Honestly said:


> Which begs the question, when would a wye primary transformer be required?


I once saw a wye to wye transformer used in an inverter setup on a solar array we installed. I don't know what its purpose was or reason for being wye was though.


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