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re: commercial capacitors

Original poster: "Dave Larkin by way of Terry Fritz <twftesla-at-qwest-dot-net>" <teslaman15-at-hotmail-dot-com>

>Firstly, does anyone know if maxwell still make HV caps? I can't find

Do GM still make cars? ;-) Maxwell were taken over by General Atomics last 
year, and the HV stuff is now marketed as General Atomics.

>any info on their page. I'm possibly interested in buying a commercial
>cap or two. My new coil would need a huge MMC (over 100 GG caps, then
>there's the soldering and stuff. This is a last resort.) I'm also
>wondering how much stray inductance an MMC this large would have. I
>would like to compare the cost of an MMC to a new commercial unit. I

Stray inductance is negligible (<10nH) when compared to the primary (10's of 
mH).  The cost comparison is basically this - Quite a lot for a big mmc vs. 
a heck of a lot for big brand new pulse caps.

>would like to get a quote from plastic capacitors, but I really don't
>know exactly what specs to ask for (the question sheet is very daunting
>- RMS current, peak current, voltage reversals, frequency, blah blah

Well, if you don't know how to spec. 'em you're gonna have a hard time 
buying 'em...  As a rule of thumb you want a DC working rating on the caps 
of 4 times the transformer rms.  For a coil of your scale you'd want them 
rated for at least 100A rms, with repetitive peak current capability of 5kA 

>blah). I have heard that condenser products still make Tesla >capacitors, 
>but they do not sell to the general public. Does anyone >know a way around 
>this? I would like a 0.15uF cap. Voltage is >currently 11.5kV RMS, but I 
>would like a significant safety margin, >and will later hopefully be using 
>nearly 20kV RMS.

Condenser Products will not sell to amateur coilers.  End of story.  However 
there are a lot of other pulse cap manufacturers out there, so no problem.  
Plastic Capacitors are the most expensive, at least 50% above the going 
rate.  I would recommend NWL, their prices are in a similar range to 
Condenser Product's were and they have some experience of building TC caps 
(Rich Hull was among their 'famous' clients).

Be prepared to pay through the nose.  Specialty pulse caps are expensive 
with a capital 'E', expect to pay 2-3 times what an mmc would cost for the 
same rating (true, the pulse cap will outlive the mmc by a factor of ten, 
but will you be alive to see either die?).  If you have your heart set on 
some big pulse caps, then surplus is probably the way to go.

>On a lighter note, the 10kW coil is progressing very well. The primary
>and secondary are completed. The primary is 15 turns 1/2" Cu pipe.
>Secondary is 1000 turns, 0.95mm wire close wound on 12" form. Sync
>rotary gap is to be finished today. Power cabinet is finished, with a
>continuous rating of 60 amps. I've started collecting HD magnets to
>investigate magnetic gaps.

Sounds good.


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