"Peter, would you happen to have some equations handy for buck/boost transformers? example, wanting to consider the rated kva for buck mode at all voltage delta configurations. I know you have more than some experience with transformers. All I have been able to grab is basic transformer equations. I would really like to be able to calculate kva for a buck/boost mode in the field from an existing transformer."
The primary of a transformer is employed to excite the core, which, in turn, is employed to excite the secondary.
The secondary is capable of supplying, in amperes, the rated secondary voltage, whether buck or boost does not matter, as these amperes will either be adding to or subtracting from the composite rating of the supply (presumed to be infinite, but certainly limited by the service, service equipment, feeder and feeder overcurrent protection).
So, the entire set of information necessary for field use is:
1) the transformation ratio, usually listed as primary voltage and secondary voltage, and
2) the rating in KVA,
both of which are specified in the transformer's nameplate.
For, if the transformation is 240 to 24 volts, then the transformation ratio is 10:1, or, simply, 10.
If that transformer was operated at 230 or even 220 volts, then the ratio is still 10, as 230 would be transformed to 23, and 220 would be transformed to 22.
So, the critical number is the ratio, not the voltage.
The wire sizes on a 10:1 transformer would also be sized to that ratio.
If the transformer was 1 KVA (1000 volt-amperes) and the primary and secondary were 240 and 24, respectively, then the primary amperes would be 1000 / 240 = 4.167 amps (small AWG, but certainly at least 14 AWG for the user-accessible conductors) and the secondary amperes would be 1000 / 24 = 41.667 amps (most probably #8 AWG, but possibly #10 AWG with higher temp insulation), respectively.
By reducing buck/boost to just the most basic rules, above, a table which derives every possible application can be made.
I'll leave that exercise to others, but, in closing, I would suggest using a spreadsheet program, such as Excel or NeoOffice or whatever, wherein the cells contain the relevant formulae, which may automatically derive the specifications for a particular application by copying and pasting the cells to other cells.