Just to clarify things for once and for all, is the transformer as described, wye:wye (star:star in UK speak) with floating star points feeding a 3-phase bridge (6 diodes in 3 series pairs with centre points to the 3 secondary phase connections and the outer 3 cathodes strapped for +ve out and outer 3 anodes strapped for -ve out?
If so, each primary will be 230V line to star point and each secondary about 10.6V line to star point. So one primary energised at 240V line to star will produce about 11V line to star on its corresponding secondary.
From this point it may be possible to rearrange the windings on several transformers to end up with a multiple of 11V from a set of series connected secondaries.
Over to the serious transformer guys now......
