Original poster: m.j.watts@xxxxxxxxxxxx
Hi Carl,
Wouldn't the control winding have to be energized with AC
to control an AC waveform?
Malcolm
On 21 Dec 2005, at 15:05, Tesla list wrote:
> Original poster: "Carl Litton" <Carl_Litton@xxxxxxxxxx>
>
>
> Does anyone on this list have any experience building saturable
> reactors for ballasting purposes? I found some older notes in the
> archive suggesting that a second winding on an iron core inductor can
> be used to introduce a variable DC voltage that will give full range
> control of the inductance as the core approaches saturation.
>
> I have been able to demonstrate the effect on a small scale with a
> simple step down transformer by putting the primary in series with a
> 120 VAC ciruit and connecting the the secondary to the rectified out
> put of a Variac. A 2.7 Henry inductor was reduced to a little less
> than 1 Henry with 140 VDC in the control winding, allowing a small
> light bulb just enough current to give off some visible light
> (measured current 0.188 Amp with no DC control and no light to 0.42
> Amp with 140VDC control and visible soft glow from bulb).
>
> However, all attempts to do this on any large (20 to 250 lbs.)
> inductors controlling a 240 volt circuit in the 30 to 150 Amp range
> have been not only fruitless but have almost instantly slagged the 25
> Amp bridge rectifier connected to the control winding.
>
> I need to understand what I am missing here. Any theory or
> especially winding diagrams of working reactors would be greatly
> appreciated. I did find one article that suggested 2 AC power
> windings in series and in phase have to be used with 2 DC windings in
> series and "out of phase" with each other in order to cancel the
> effect of induced AC in the control winding. But here again, no
> practical application, turns ratios, winding configurations, etc.
>
> Any thoughts?
>
> Thank you,
>
> Carl Litton
>
> Memphis HV Group
>
>
>