I twas afraid this might come up (because I am unsure of the proper approach).
Controlling phase of the AC mains on the primary side of the transformer is
done, but I do not know the pitfalls.  It will probably cause horrible power
factor figures, and will generate a lot of RF.  Will the transformer have to be
better or higher bandwidth than a simple fillament transformer?  The up side is
that you can put SCR's on the primary side and just rectify the output with
relative ease.  And the frequencies are lower.  And if the phase control method
has poor speed respinse (suspect that is why they are not common in PSU's) who
cares?  The cars will not know the difference.

Chris Eddy

Michael Wieser wrote:

> I used a normal 15V/40A transformer with an dimmer in front (the basic can
> be found on www.sts.com, AN 308, I replaced P1 in figure 11  with an
> optocoupler)