The main transformer produces an AC square wave, and a driver circuit is used to control the saturation of an inductor to regulate the output voltage.
It is interesting that changeing the saturation we can change conductivity in continous way without disconnecting load from mains if I understand it well.
Here it is another article about
Magnetic Amplifiers: How They Work, What They Do dated to July 1960
![Wink ;)](https://www.eevblog.com/forum/Smileys/default/xwink.gif.pagespeed.ic.cldandycH0.png)
This magamp schematics from these days shows exactly how transformer wires are connected with rectifier diodes and load in AC circuit to form full-wave magnetic amplifier.
![](http://www.rfcafe.com/references/popular-electronics/images/magnetic-amplifiers-jul-1960-pe-9.jpg)
I think it is worth spend a while and test this using transformer with known core hysteresis and maybe AC sinus signal generator at higher frequency lets say 10kHz with fast Shotky rectifiers-than much less power turns are needed I guess and it might work, while now it is clear how these two power coils and controll coil in the middle are connected
![Cool 8)](https://www.eevblog.com/forum/Smileys/default/xcool.gif.pagespeed.ic.cOxV6sPNRd.png)
Update: I've found nice (iron?) E core transformer from microwave oven teardown
![Evil >:D](https://www.eevblog.com/forum/Smileys/default/xevil.gif.pagespeed.ic.tdrs7Uj5gu.png)
![](http://s5.postimg.org/69qf6cdib/microwave_oven_transformer_forum.jpg)
It has 10.5cm2 outer core area and 21cm2 in the middle.
It looks like there is about 144 turns @ its primary 230VAC coil (2.3 Ohm).
If I remove high voltage coil by cutting welder tracks at the bottom than I could easy add another power coil and controll in the middle for testing.
Just wondering what magnetic relative permeability
u/u0: 200-1000 of this microwave transformer core (iron?) might be for calculation?
BTW: Started read this excelent book
"Magnetic Amplifiers - Principles and Applications - 1960" by Paul Mali and it explains a lot.
It is time to
![Tweak :-/O](https://www.eevblog.com/forum/Smileys/default/smiliey_cal.gif.pagespeed.ce.yYMcAvxBJk.gif)
and
![Broken! :-BROKE](https://www.eevblog.com/forum/Smileys/default/smiliey_scope_broke.gif.pagespeed.ce.z9RuKVWKjY.gif)
those transformer magamps
![ThumbsUp :-+](https://www.eevblog.com/forum/Smileys/default/icon_smile_thumbsup.gif)
However, it is always worth to see and hear nice looking girl in electronics lab which seams to know howto not to destroy oscilloscope
![Grin ;D](https://www.eevblog.com/forum/Smileys/default/xgrin.gif.pagespeed.ic.QVVz6XIT20.png)