Hi guys, i was studying on transformers losses, i in some

[aaqeel123]

hi guys, i was studying on transformers losses, i need help in some problems.

why open-circuit test show only excitation losses and not i2R losses..

thanks...

 

[Phrak]

What reference are you referring to that seems to ignore copper losses?

 

[jim hardy]

think about that for a moment

what is magnitude of current in open circuit test?

just magnetizing current 'cause there's no load on transformer...
which for a quality transformer should be small (though not zero)
and when you express it as a fraction of rated current and square that it gets even smaller


so if your text did not state that the magnetizing current is small enough to ignore then it was an error of omission by the author,

and it is not always the case that magnetizing current is negligible...