Transformer Terminal Ratings

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ryangittens

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usa
I have a 150KVA transformer connected to inverter at 480V sec and utility at 208V pri. I am wondering if I can size the conductors based on 90C or 75C.

On the spec it says, "Temperature Rise 150C with 220C Insulation System." Does this have anything to do with the terminal ratings? Or do I just assume that it's 75C?

Capture.jpg

Thanks for any help.
 
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Carultch

Senior Member
Location
Massachusetts
ryangittens said:
I have a 150KVA transformer connected to inverter at 480V sec and utility at 208V pri. I am wondering if I can size the conductors based on 90C or 75C.

On the spec it says, "Temperature Rise 150C with 220C Insulation System." Does this have anything to do with the terminal ratings? Or do I just assume that it's 75C?

View attachment 17210

Thanks for any help.
Click to expand...

Those temperatures have nothing to do with terminal ratings. That is the winding temperatures. 150C is the full load temperature rise above ambient, and the insulation system rating is the maximum rated temperature at which the insulation system is safe (dielectric fluid and other internal electrical insulators inside the transformer).

I would assume the 75C rating unless you know for a fact you can use the 90C rating.

You do install on separately installed connectors, which are likely 90C rated, and that would lead me to believe I could use the 90C rating. But just because a connector is 90C rated, doesn't mean you can use the 90C terminal rating. The equipment itself needs that rating. The only time I anticipate using the 90C rating for anything other than derate calculations is if the termination is in an otherwise empty enclosure.
 
augie47

augie47

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Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
On what device do the conductors terminate on the other end ?
 
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