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Re: "Taming the MOT"
Tesla List wrote:
>
> Original Poster: "M Fabs" <the_machin_shin-at-hotmail-dot-com>
>
> My understanding of Finn Hammer's saturable tranny is this:
Just for the record: It is not my design, I am not that smart!
>It is current limited by virtue of the (magnetic) short circuit created by
the core
> material that passes through the choke windings.
This is true: The iron in the choke cores is unloaded, therefore they
offer a sweet low-reluctant path for the flux, generated by the
secondary windings, to travel. The choke coils alone are large enough to
provide the necessary inductance in the primary windings. The power
winding will fight a loosing battle trying to get power out, because the
flux will prefer to trawel in the choke coils.
That is, untill we apply DC flux in them, increasing the reluctance of
the material, thereby allowing an equal increase in flux in the power
core, resulting in more power to the secondary winding.
> This looks EXACTLY like
> the current limiting shunts in an NST, right? Adding a choke coil allows
> for controlled saturation of the shunts, increasing the saturation of the
> shunts reduces it's capability for conduction of flux lines, so more flux is
> forced into the secondary winding.
>
> What about this... (Fixed width font!!)
>
> +++++++++++++++ +++|+++ +++++++++++++++
> + + + | + + +
> + +++++++++++++ + | + +++++++++++++ +
> + + PPP CCCCCCCCCCC SSS + +
> + ++PPP++++++++ + | + ++++++++SSS++ +
> + PPP + + | + + SSS +
> + PPP + + | + + SSS +
> + PPP + + | + + SSS +
> + PPP + + | + + SSS +
> + ++PPP++++++++ + | + ++++++++SSS++ +
> + + PPP CCCCCCCCCCC SSS + +
> + +++++++++++++ + | + +++++++++++++ +
> + + + | + + +
> +++++++++++++++ +++|+++ +++++++++++++++
> "E" "I" "I" "E"
>
> NOTE: proportions look a little strange, but # of +'s gives relative cross
> sectional areas of the core components...
>
> This is supposed to be two MOT cores, open "E" faces separated by the two
> "I" sections paralleled (or a center leg, all else cut away, of a third
> mot). Primary (P) and Secondary (S) are both MOT original primaries, and
> the choke coils (C) can be anything that will fit (other primaries, hand
> wound, etc). Would this function in much the same way as Finn Hammer's
> arrangement? (Hopefully with less cutting...) The "I" sections ought to act
> as current limit shunts until the choke coils saturate them, forcing more
> flux through secondary.
I am not an expert, but I don`t think this would work. The reason for
using 2 choke coils is, that the alternating flux set by the primary
runs in opposing directions in the choke coils, therefore largely
cancelling each other out, such that there is no AC induced into the
choke-coil. In your arrangement, the chokecoils are just part of the
transformer, they could as well be positioned on the outher legs. The
way I see it, if you try to make this on one core, either you have AC
on the choke coil, or you have DC canseling = no saturation.
>
> If this will work out, what should the phasing of the choke coils be?
> Probably dont want to have them out of phase, they would just steal all of
> the current. Are two DC supplies necessary in this, or could they just be
> wired in phase, and driven from the same dc supply? What specifications for
> the DC supply would be required?
The patent tells apout how to avoid the ac voltage in the chokecoil, but
I didn`t pay attention, with the full cores that I cut yesterday. This
was stupid, because it was 23 volts, and that blew my 10 amp. regulated
lab supply. I think that getting close matched choke cores is paramount,
and that the shunt winding around the chokecoil is a very prudent idea,
too.
>
> Is this an inexpensive substitute for a variac (less cost of DC supply), or
> am I missing something fatal...
I am not shure, if it is inexpensive, (but it is elegant) but it serves
the purpose, that is otherwise taken care of, with variacs, welders and
whatnot.
>
> Thanks for your thoughts and questions!
>
> MPF
> the_machin_shin-at-hotmail-dot-com
>
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