MOTs and ballasting

["Tesla list" <tesla-at-pupman-dot-com>]

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.





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