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Re: MOTs and ballasting



Original poster: "Joel Andersson by way of Terry Fritz <teslalist-at-qwest-dot-net>" <andersson.joel-at-telia-dot-com>

Hi Steve,
IMO, MO caps is the way to go, I use 4 of them in my 4-MOT supply:
http://hot-streamer-dot-com/temp/Redbox001a.jpg
I get about 4.5 kva from this, I have a 230V 16A line so I can't go higher.

Since the MOT secondaries are all in series it doesn't matter where you put
the ballast, current is the same in the whole circuit.
But there may be to much voltage on the caps with only one per side, so four
caps in series/parallell would be better. (MMC ballast? :-))

I used a 2-MOT + doubler supply with a third MOT as ballast before and I
tuned my coil with the secondary on the ballast MOT open and the gap set
very small.

  Looking forward to see the results as I've been thinking of building a twin
myself, got any good links?

Good luck

Joel

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, April 19, 2003 5:12 PM
Subject: MOTs and ballasting


 > Original poster: "Steven Ward by way of Terry Fritz <teslalist-at-qwest-dot-net>"
<srward16-at-hotmail-dot-com>
 >
 > I really hate to bring this topic up again, as im sure its been talked
 > about a lot.  But i think my case is slightly different.  Im working with
a
 > friend on a large twin coil.  We have 4 mots for a 5-6kva supply
 > (hopefully).  We have a 240V 50A line.  But, as one could imagine, the
 > ballast is going to be a pain to design.  We do have a new roll of 500ft,
 > 10ga solid copper wire.
 > Has anyone tried such an air core inductor?  Or, our other option is the
MO
 > cap ballast that Greg hunter used.  But, we want over 5kva!  So, some
 > questions about this capacitive ballast.  1) why is there only a ballast
on
 > the first set of mots???  Wouldnt that only ballast the first pair?  Or
 > would the second pair only put out the same current as the first?  2) can
 > we use a value of only .97 (2kv) on each of the first 2 MOTs?  This would
 > give the largest amount of current output.  Or would we have to actually
 > parallel 2 caps?  Im wondering, will the caps see voltage spikes, and
 > excessive currents (like above the few hundred ma)?  Any help on designing
 > a 5+kva MOT 4 pack is really needed.  Are there any sites that have done
 > what i need to do???  Oh, and we dont have a variac (i know, bad news).  I
 > do have a 280v 25A relay though, but its not a variac.  Does anyone have a
 > recommended method for proper setup before i hit the switch?  I would
 > assume, use some extreme ballasting, get the coil tuned up as best as
 > possible, then try full power.
 >
 > Just a thought,  MOTs themselves are current limited to some degree by the
 > shunts in them.  Do you suppose that we could run without a ballast, and
 > get whatever the MOTS will dish out (probably no more than 6kva)?
 >
 > Oh, and has anyone used PFC on a mot supply?  I really hate to pull THAT
 > much current if i dont have to.  I think Java TC said something like 250uf
 > or something, will it really work though?  Ive used the PFC on my 2kva
 > coil, and it worked awesome, but that is with NSTs.
 >
 > Im looking forward to some 10-12 footers ;)
 >
 > Steve Ward.
 >
 >