Re: Single Phase Transformer Question.
If a neutral is not connected from pri to sec. Which it is not!
The secondary is a seperately derived system. The secondary also appears to be a single phase 3 wire (two hots and a neutral).
The pri feed is just two lines from a three phase network. This is a single phase transformer. I'm not sure which formulars you are attempting to apply to the pri. If you wish to determine power in VA drawn from the pri source then , you would use a single phase kVA formular kVA=VA/1000 because you are only evaluating two line wires , you already have the line voltage, and a third line conductor is not brought to the pri.
This single phase formular is also used for the seconday.
If (for some reason you wish to evaluate the entire three phase network feeding the transformer a formular for three phase systems may be necessary.kVA= VxAx1.73/1000
Charlie