Re: Mad NST!

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

Original poster: "Alexander Rice by way of Terry Fritz <twftesla-at-qwest-dot-net>" <alex-at-rices.myip-dot-org>

05/06/2002 06:00:12, "Tesla list" 
<tesla-at-pupman-dot-com> wrote:

>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.

hi steve

By removing turns from the primary (the 
turns removed rom the secondry are such a 
small proportion if total turns it doesnt 
matter) you have increased the voltage of 
the transformer by (3/15)*100 = 20% or in 
other words it is now putting out around 
1440v with a peak voltage of 20,700v 
whaich explains the ability of it to jump 
an inch in air. It alsom means that the 
core is saturating and drawing an obscene 
amount of current. All you need to do is 
to re wind the 3 layers of primary 
windings you removed with some fresh wire 
and all will be well.

regards

alex
------------------------------
Alexander JJ Rice
Geek#-1232
Rank : G-2 (Wahey!)
http://www.TheGeekGroup-dot-org
"Because the Geek Shall Inherit the Earth 
!"?