# Need a 340 KVA iso transformer



## Bbsound (Dec 16, 2011)

Looking for ideas to help bail out the engineer on a job we have. 

Short story: I need to create a neutral for a 340 kva load from a 3 wire 3 phase distribution. 

Longer story: Installing a CT in a hospital, engineer planned to pull the circuit from the critical emer branch. The hospital said no, put it on emer equip branch. We investigated and found emer equip branch has no neutral in entire system. 
So now we need to help figure out how to make this happen. 
Only iso transformers we have found so far are 300kva next size is 500kva which is going to be a bitch just to get into the building. 

Obviously this is the engineers problem, but this is somebody that we work with VERY often and want to help him out.


----------



## l0sts0ul (May 7, 2011)

Pull a system ground from the main source, and change transformer to a disty... only thing I can thing of...


----------



## Vintage Sounds (Oct 23, 2009)

No neutral? Is it a delta? In that case would a zigzag transformer work in a situation like this?


----------



## brian john (Mar 11, 2007)

l0sts0ul said:


> Pull a system ground from the main source, and change transformer to a disty... only thing I can thing of...


First what is a DISTY and how do you change a delta/delta to a DISTY?

Second the transformer should already have a ground.

Third what to heck would doing what you say do, for a neutral?

YOu can do utilize a zig zag transformer for a neutral, I have bid on this in the past but the zig zag was not for neutral for loads but for grounding. The corner grounded delta was not operational with a new chiller.

If a 300 is two big you could utilize two 225's,, but there are some very specific rules involved when paralleling transformers.


----------



## Bbsound (Dec 16, 2011)

Its is a regular Wye service, pretty large 7 story building. They just did not include a neutral with the equipment branch of their emergency power distribution. 

Thanks for the replies, but I don't think we can offer a relatively inexpensive option.


----------



## micromind (Aug 11, 2007)

Bbsound said:


> Its is a regular Wye service, pretty large 7 story building. They just did not include a neutral with the equipment branch of their emergency power distribution.
> 
> Thanks for the replies, but I don't think we can offer a relatively inexpensive option.


If the center of the wye is already grounded, a zig-zag might not work. As far as I know, a zig-zag needs to be connected to an ungrounded 3 wire system, and the newly created center of the wye is then grounded. 

Since a aig-zag is not isolated, there can be only one neutral to ground connection, not two.


----------

