480/277 in power is 200 and i have a115 kva and i want 400 amps out out put is 313 will this work?
- Thread starter mqbond007
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iceworm
Curmudgeon still using printed IEEE Color Books
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- North of the 65 parallel
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- EE (Field - as little design as possible)
Rephrase your question a bit
Here is what I think I got:
115KVA transformer
primary voltage is 480V, 3phase
Primary winding Wye or Delta ??
Primary feeder CB 200A
Secondary Voltage??
Secondary winding Wye or Delta ??
Secondary FLA need to be 400A ??
I have no clue what the "313" refers to.
We will need the data with the question marks filled in
If you have a transformer dataplate - a picture of that would be a good start.
Or just the information from the dataplate.
Here is what I think I got:
115KVA transformer
primary voltage is 480V, 3phase
Primary winding Wye or Delta ??
Primary feeder CB 200A
Secondary Voltage??
Secondary winding Wye or Delta ??
Secondary FLA need to be 400A ??
I have no clue what the "313" refers to.
We will need the data with the question marks filled in
If you have a transformer dataplate - a picture of that would be a good start.
Or just the information from the dataplate.
texie
Senior Member
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- Fort Collins, Colorado
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- Electrician, Contractor, Inspector
313, 899, whatever. Just wire it up and see if any smoke comes out.
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
No
Read the data plate
Secondary FLA is 312A
The transformer will have to be overloaded to 128% to get 400A
The transformer is already a high temperature unit, 150C rise above a 40C ambient, 190C = 374F
And you are going to overload to 128%, so it will be much hotter. I don't know how much hotter.
I don't know how long it will take to fail. Maybe a day, maybe a month
And it will smell really bad
Read the data plate
Secondary FLA is 312A
The transformer will have to be overloaded to 128% to get 400A
The transformer is already a high temperature unit, 150C rise above a 40C ambient, 190C = 374F
And you are going to overload to 128%, so it will be much hotter. I don't know how much hotter.
I don't know how long it will take to fail. Maybe a day, maybe a month
And it will smell really bad
electrofelon
Senior Member
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- Cherry Valley NY, Seattle, WA
Do you really need the full 400 amps? Is that actual or calculated? If that's calculated it will likely be fine.
- Location
- San Francisco Bay Area, CA, USA
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- Electrical Engineer
You must mean that you have a 200A circuit breaker feeding it. The input current is only 135.3A at full rated capacity of 112kVA. So if you are measureing that it is drawing 200A on the primary side, it is already overloaded.
- Location
- Connecticut
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- Engineer
A 200A primary c/b and a 400A secondary c/b is Code compliant.
iceworm
Curmudgeon still using printed IEEE Color Books
- Location
- North of the 65 parallel
- Occupation
- EE (Field - as little design as possible)
David is correct - Obvious brain failure on my part. I don't know what I was thinking.
QUOTE="iceworm, post: 2554219, member: 114227"
Revised
Primary CB
Primary is 135A
2.5 x 135 = 338A
200A CB is okay
Secondary CB
FLA is 312A
1.25 x 312 = 390A
400A CB is okay
The transformer will have to be overloaded to 128% to get 400A. and it will get pretty hot.
400A on a 400A CB is inviting a trip, but it could take a few hours, however, it also might never trip.
Just need to make sure the conductors are suitable - ampacity is equal to the CB, or more
Yes, it may well smell hot. And it will burn if you touch it.
The life will be reduced - I don't know how much.
But it will work - possibly for several years.
powerpete69
Senior Member
- Location
- Northeast, Ohio
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- Professional Electrical Engineer
I think OP means he has 200 amp primary breaker and 400 amp secondary breaker. Will this work with 312 amp secondary max?
Yes it will.
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