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Mad NST!



Original poster: "Steven Ward by way of Terry Fritz <twftesla-at-qwest-dot-net>" <srward16-at-hotmail-dot-com>

Hello all,

As of now, i have had 2 successful NST re-builds(out of 2 tries).  MY first 
was a 9000v 30 ma France, i depotted and made it a 9/50.  It works nicely, 
and i have no problems with it(obviously not why im writing).  But the 
transformer that i have recently fixed is a 12000v 30 ma france, that had 
one bad secondary.  It was actually my friends transformer.  After he made a 
crude attempt to fix it, he gave up and gave it to me.  He ended up damaging 
both a secondary and the primary.  I fixed the primary by removing 3 
layers(out of only ~15-18 total layers), since he peirced it deeply with a 
screw driver.  He pierced one of the secondaries as well, it was fixed in 
the same manner, this time removing about 10 layers to get to continuity.  
So to even out the secondaries, i removed ~ 10 layers from the other coil.  
They both read ~ 7k ohms.  Now getting to the problems.  When i powerd it 
up, it worked great, then, an arc shorted the inner most part of the primary 
to the core(poof!!!).  So I fixed that and re-insulated it with some 
electrical tape.  This wanst enough as it happened again when in TC use.  
BTW the transformer is drawing over 7 amps as of then!!  Thats way more than 
what it is rated, and i have not removed any shunts.  So after the 
insulation went out, i put some thick plastic like i did for the 
secondaries, around the coil.  To do that, i had to remove 3 shunts from 
each pack, to fit the insulation.  Now the tran draws 12 amps!!!!  What the 
hell is going on?!?!  Im almost positive that my meter is fine.  Also, is it 
normal for it to be able to start an arc at 1" distance?!?!  Each secondary 
can arc about .5" to the case easily.  I can draw the arc nearly 4".

First of all, 7A from a 3A transformer is way too much, even without PFC.  
But now that its drawing 12A im starting to get scared!  Does anyone know 
why its doing this.  I figured that its because i removed a lot of wire.  
But i really dont think that its very safe for this thing to be drawing 12A. 
  Also, judging from the 1" arc lenght, how much voltage do you think that i 
have??  My 9000v 50ma unit can barely start a .5" arc under the same 
conditions, and it isnt nearly as powerful looking as this transformer.  Any 
thoughts are welcome about my little situation.  Thanks,

By the way, what is the average power draw from a 360VA transformer with out 
any type of power factor correction.  If its 2x the rating(6A for a 360VA 
tran) then the 7 amp reading makes sense if i figure i removed 15-20% of the 
primary winding.  Also the 15-20% winding removal would calculate a 14400 
volt output, which almost seems right with that long of an arc length.  I 
wonder if i didnt just solve my problem???  but 12A is still really high!!  
Help is probably still needed.

Steve Ward.