> If I place the 110 primaries in series and also series the
> secondary using
> the common connection on the secondary as a CT, would
> equalizing the
> currents in the transformers be necessary if the secondary
> voltagse of the
> transformers differed more than say 25 volts or so.
When using a grounded CT, you give up supply regulation
compared to paralleling the windings. So I would not use
that method, it wastes transformer copper since for 50% of
the total on time one winding is doing nothing at all.
Parallel with a bridge is the only way to go if you want
good regulation.
If you series either primary or secondary pair or series
both primary and secondary pairs, you don't need a separate
bridge. It does no good at all.
> Another question: If the secondary voltages differed more
> than 30 or 40
> volts and I used separate bridges, how much of a potential
> problem would
> that be?
Not much. The ESR of the transformer, which includes primary
and secondary resistances and core losses, and is always
more than the dc resistance of the secondary (so you could
use that as a conservative easy to measure value). This
resistance equalizes currents. If the voltage drop from no
load to full load was 300 volts dc and there was only 30
volts open circuit voltage difference, you would have less
than a few percent difference in transformer power loading
when using separate bridges.
The difference in no load voltages would have to be a large
value compared to the dc voltage drop under full load for
the transformers to be unbalanced when using separate
bridges. I think you are worrying about nothing. The only
condition that is a problem when using similar transformers
is when both the primary and the secondarys are paralleled.
73 Tom
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