240 volt service without neutral

[aarifisher]

I am installing a step down transformer 75 KVA in order to get a neutral
primary: delta 240 Volts - secondary: why 208Y120 Volts
to my calculation I need 180 Amps for line side 75,000 / 415 (240 X 1.732 = 415) And 208 Amps for load side 75,000 / 360 (208 X 1.732 = 360)
I just wonder if that's correct
because when i checked out the transformer the line side lugs where a lot smaller then the load side and the same is for the internal wires of the line side?

thanks

 

[augie47]

Your calculations are correct, of course, the size of your overcurrent device will also be prevalent in determining wire sizes. { Note the last sentence in 240.21(C) }

If I observed the lug and wire sizes you note, I would double-check to assure I did not accidentally received a transformer with a 480 primary since they are by far more common.

 

[aarifisher]

If I observed the lug and wire sizes you note, I would double-check to assure I did not accidentally received a transformer with a 480 primary since they are by far more common.

yes I did and its the right transformer, I didn't check what size the lug is but the they are by far to small for 3/0 or 4/0 wire, should i just change them out?

 

[jim dungar]

I was under the impression that most 75kVA transfromers were sold without fatory installed lugs.

 

[aarifisher]

I was under the impression that most 75kVA transfromers were sold without fatory installed lugs.

this one came with the lugs installed and i have seen it come a lot of times

 

[kwired]

Usually the lugs are field installed, but in this case maybe an assembly mistake - they likely assemble many more that are 480 volt primary and just installed the usual components?