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Re: "Taming the MOT"



My understanding of Finn Hammer's saturable tranny is this:  It is current 
limited by virtue of the (magnetic) short circuit created by the core 
material that passes through the choke windings.  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.

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?

Is this an inexpensive substitute for a variac (less cost of DC supply), or 
am I missing something fatal...

Thanks for your thoughts and questions!

MPF
the_machin_shin-at-hotmail-dot-com

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