[Amps] 3P transformers on 1P: brain twister for the day....

[DAVE WHITE]

Guys

As a change from whimsical vermin control discussions, I have a different question.  A few weeks ago - and around a year ago - there were threads asking all about use of 3 phase transformers on single phase.  Did we ever reach a reasoned conclusion?  This question has banged around in my head and like the proverbial terrier (oops nearly onto rats and snakes again) I don't like to give up....

An RF/power engineer I know in Bradford (Paul Whitely of bowler hat and pinstriped suit at the Friedrichshafen fleamarket fame) told me that - assuming a delta primary and star secondary - that I'd get (input voltage / design voltage) times (root 3).  Again the assumption is that I wire two primaries in parallel and take two secondaries in series.  This is from memeory so I  could have got it wrong.  So: a 380v 3P input with a 5kv 3P output run this way on a 1P 230v input would give me: (230 / 380) * 1.73 = about 5.2kv.  RIGHT OR WRONG?

Does anyone have a rigorous calculation to prove this along with the reasoning behind it?  I'm just curious.  When I first asked the question of the group, I thought I may be able to scrounge an old pole pig transformer off the local power company.  Sadly bureaucracy, SAP (the same thing really) and the dreaded 'Elf 'n' Safety seem to have taken over and I doubt that one will come my way.

Also, what's the likely current handling capacity compared to spec?  Does anyone have G3RZP's email address?  I bet he'd know.

cheers

Dave G0OIL