Transformer question

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jparker83

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Ok guys,

I've got a little problem here. What I am trying to do is power a project I am working on that has a total load of 100 Amps, which will probably be running 72-80 amps at all times. I need to supply everything with 120VAC single phase. So simply put, KVA equation would say I would need 12KVA transformer. Simple right. This is where it gets a little tricky. I am given by the company a 480 Delta supply. now to get 120, I would need a delta to wye transformer that does this would be 480 Delta/208 wye. At what KVA will this be rated at to make the total 100 amp load work? I have picked out a 15KVA transformer, but I want to be sure

I may have answered my question, I just want verification.

Thanks
 
When you say that you need to supply everything with 120V single phase, do you mean that the entire load _must_ be on the same 120V single phase supply, or do you mean that you have a bunch of different loads, which all require 120V, but that the loads may be supplied by separate phases?

In other words, do you require a 120V 100A supply, or could you use a 208/120V 35A supply, which provides a total of 3 120V phases, 35A each?

-Jon
 
winnie said:
When you say that you need to supply everything with 120V single phase, do you mean that the entire load _must_ be on the same 120V single phase supply, or do you mean that you have a bunch of different loads, which all require 120V, but that the loads may be supplied by separate phases?

In other words, do you require a 120V 100A supply, or could you use a 208/120V 35A supply, which provides a total of 3 120V phases, 35A each?

-Jon
Click to expand...
I could split between the phase, and just run different items on different phases. thats no problem, I just want to see if the transformer I picked out will work for the application I working towards.
 
A 15KVA 480 delta to 208/120 wye transformer has a nominal secondary rating of 42A per phase.

You will need to determine if you can split your loads up so that no single phase has greater than 42A loading.

-Jon
 
jparker83 said:
Ok guys,

I've got a little problem here. What I am trying to do is power a project I am working on that has a total load of 100 Amps, which will probably be running 72-80 amps at all times. I need to supply everything with 120VAC single phase. So simply put, KVA equation would say I would need 12KVA transformer. Simple right. This is where it gets a little tricky. I am given by the company a 480 Delta supply. now to get 120, I would need a delta to wye transformer that does this would be 480 Delta/208 wye.
Click to expand...
Why use 3-phase if you only need a single phase supply?
Why not get a 480V to 120V single-phase 12 kVA transformer?

I you have already got a 15kVA 480V/208V 3-phase DY transformer then, as Winnie says, you are limited to 42A maximum on each phase
 
JParker,
If your load is 12KVA, working with a 15KVA transformer,
then the the system is 15KVA, split amongst the three secondary phases,
about 42A each phase.
If primary KVA is 15KVA, then the secondary KVA is 15KVA.

Yes, you sort of answered your own question.
That is a good talent!

...

...
 
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