On Sat, 22 Apr 2006 20:58:04 GMT, Ignoramus8092
wrote:

Thank you Guy. My plan is as follows: wire the transformer as three
phase Wye, and use three SCR half bridges in a scheme similar to that
by PCTI. These three half bridges will be added without disturbing
current SCRs.

I have six secondaries, two on each leg, I will parallel each pair.

Does it make sense?

i

No. Wiring the transformer as (a single) Wye requires having access
to all 6 secondary leads on each transformer half (12 secondary leads
available vice the 6 I think you actually have) so you can reverse the
phase on one half (switch the neutral connection with the 3 line
connections on one side) so they can be paralleled. This will totally
screw your existing 6-phase rectifier of course. I suggest you
re-read the description by Lawrence of how the 6-phase system works
(previously posted to ABSE).

You now have 2 separate 3-phase Y secondaries of opposite phase, if
you wish to add a separate SCR rectifier of standard 3-phase design
without screwing your existing rectifier you will need two of them,
they cannot be paralleled. The DC output of two separate rectifiers
can of course be paralleled.