Using magnetic saturation for current regulation.

[Chris Bradley]

I am in the process of building up some power supplies and was wondering if I could add current regulation by the following means. [The voltages are HV by IEC standards (viz. 1- 5kV) but not 10's of keV.];

Creating resistive dissipation for current regulation presents various difficulties in the circuits I'm building so I was thinking about the possibility of saturating a transformer with a DC bias on an isolated coil instead to regulate its total output. Much along the ideas of the magnetic amplifier.

It's just a thought. I'm not aware that it is a method used for such a purpose so that probably means there is no point trying!? Any comments?

best regards,

Chris MB.

[bpaddock]

Chris Bradley wrote:
>I was thinking about the possibility of saturating a transformer
>with a DC bias on an isolated coil instead to regulate its total output.
>Much along the ideas of the magnetic amplifier.

>Any comments?

http://en.wikipedia.org/wiki/Saturable_reactor

Do a search for 'Metglas' as well.

SR/Mag Amps are still used in high voltage, ultra fast pulse applications
due to their survivability. Sometimes a Saturable Reactor is used in conjunction with
power FETs/IGBTs to delay current flow long enough for the gate to become
fully charged to avoid "hot spots" that would destroy the part.

Check out the Mag Amp. stuff here:
http://www.teslapress.com/catalog.html

http://en.wikipedia.org/wiki/Magnetic_amplifier


Bob Paddock

[bwsparxz]

I believe that Carl Willis used a mag-amp on his first fusor, in fact I saw it. Maybe Carl could chime in on this.

[Carl Willis]

Hi Chris,

Brian mentioned the mag amp I used on my first fusor, which was located in series with the x-ray transformer primary. I think Thiago Olson has it now.

It was salvaged from a big Lepel induction heater power supply. The DC bias I used was something on the order of 0-60 V, 0-200 mA. This current flowed in two balanced coils that, due to their winding sense, produced no net EMF from induction from the third (AC) coil. The mag amp did its job as a variable inductive ballast / power limiter very well.

-Carl

[bwsparxz]

Here's a link to building a saturable reactor (mag-amp).

http://www.dawntreader.net/hvgroup/satu ... actor.html

[Chris Bradley]

Thanks for all the replies. Looks like I'm on established ground to kick of a few tests. That last link is super. I have an old 110V-220V-240V-2kV power transformer, originally a linear amp drive which looks like it has good high current windings on it and with twin isolated bobbins, so will dust that off and try a few things out.

Many thanks,

Chris MB.