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Re: [TCML] Questions about saturable reactor / magnetic amplifier

Hi Dr.Resonance,

now I am absolutely confused - because in the list archives I have found the following mail of you where you have written that it is a very good alternative to a mechanical moving gapped core. This sounded to me to be exactly what I want, maybe you could explain this again in detail:

"yes, we do this very procedure using an old 10 kVA core that we strip all the windings off of. We then rewind the two outer legs with 90 turns (total split between the two legs), and use a 32VDC 10 Amp power supply which energizes a winding on the central core leg. This gives us total and smooth electronic control from 0-70 Amps at 220VAC. It works excellent and eliminates our older method of using a gear motor to move the core in and out of the coil."


----- Original Message ----- From: "DC Cox" <resonance@xxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Wednesday, August 18, 2010 9:25 PM
Subject: Re: [TCML] Questions about saturable reactor / magnetic amplifier

Usually a gapped core non-saturable reactor is required. Cores without gaps
just don't seem to perform very well as the pole xmfr hits peaks the core
saturates and allows peak currents 10 to 50 times the average current.

We use laser cut C-Cores and usually set each gap around 60-80 mils
depending on total current limiting required.

Dr. Resonance

On Wed, Aug 18, 2010 at 12:07 PM, Teslalabor <teslalabor@xxxxxxxxxxx> wrote:

after several months searching for a suitable transformer for modification
into a saturable reactor, I now have found a big 3-phase welding
transformer, which was in use on 3-phase 400V here in Germany.
For my big teslacoil, which runs on 2-phase 400V, I want to modificate this transformer into a magnetic amplifier. The goal is, to control the current through the outer legs of the transformer @ 400V from 0-60 Amperes whith a
DC current of 20A on the middle leg of the transformer.
Today I removed the heavy welding windings, and put the two outer legs of
the transformer in series and connected them on 400V. On the middle core leg
of the transformer, I wound a winding of several turns and applied 20
Amperes DC to it. I measured the 400V - current trough the outer windings,
and it arrised from 0,5A to 10A, when I regulated the DC from 0 - 20A.

There was something strange to me: The current in the 400V windings firstly
raised very fast when I raised the DC and then only very smoothly.

I then doubled the windings on the DC winding. I got the 10A in the 400V
windings at only 10A (instead of 20A before) but it only increased to 12A
when I pulled the DC to 20A. In the same way: firstly very rapid current
rising, than only 2A from 10A to 20A DC. Why this? How many thousend turns
do I need for reaching 60Amps in the outer 400V windings? Is it even

Best Regards
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