Re: Cap Confusion

Tesla List wrote:
> >From DELCOKEVIN-at-aol-dot-comSat Aug  3 07:00:12 1996
> Date: Fri, 2 Aug 1996 16:01:24 -0400
> From: DELCOKEVIN-at-aol-dot-com
> To: tesla-at-pupman-dot-com
> Subject: Cap Confusion
> Originally starting out as a letter to Richard Hull,
> I thought the group might want to put their 2 cents worth in,
> and or hear about the following.
> Richard,
> I am specing and pricing out 2 .1uf caps.
> Questions for the weekend:
> Condenser Products state that their caps that are rated for 20KV AC RMS
> are good for a peak DC voltage of 135 KV.(I believe he said 34 mil plate
> spacing).
> NWL states that for my 20KV AC RMS xfmr they would give me a cap
> that they rate as 60KV AC RMS good for a peak DC voltage of 85 KV.
> How would you explain these differences?

NWL is my cap company because they charge more and you get more!  More in 
the conservative nature of their specs.  They don't wnat to have to do it 
"twice" when their work comes undone!  This is no bad reflection on 
anyother manufacturer as long as they warrant their work. - R. Hull

> Which would you go with, based only on this, so far?

Your call only as it is your money -R. Hull

> NWL eng's will be getting back ahold of me Monday.
> Condenser Products eng seemed very familliar with Tesla applications.
> They are specing a .1uf cap good for 110 amps rms for 2 min intervals
> 5 min rest, 500 bps ascyronous gap. Terminals will be 1" copper fittings
> due to the temp and current and skin effect he stated that 1/2" brass
> would get too hot. (Why did you spec smaller 3/8" terminals for caps
> rated at higher currents? or why would their eng spec so large terminals?)
> Here is where CP has the edge.  They know Tesla coils.  They court the 
business!  NWL is unfamiliar with TCs and they over spec the stuff for 
tough operation beyond a simple spec.  The terminals should not heat in a 
well constructed system.  Brass or copper of the small surface found in 
these caps, will not dissapate much energy. -  R. Hull

> NWL, for a starting point I gave them the same criteria, but told them I
> wanted 400 amps rms -at- 150khz. (figureing that if the price was too high, I
> could
> go down to 110 amps rms -at- 130 khz)
> Both NWL eng's seemed very knowledgeable, but did not know a thing about
> Tesla coils. (they do recall making your caps) and I explained exactly how a
> standard Tesla coil worked)
> The currents I can jostle with on my own, but I wanted your input on the
> voltage situation, as it is not appearing to be apples to apples.
> CP's caps are rated for 125000 amps peak with 100 nH internal inductance.
> NWL will spec 70,000 amps peak with an unknown internal inductance.
> Is this a difference worth worrining about?

Not really for TC work.  For water arc work, Yes!  - R. Hull
> As far as using these caps later on for pulse discharge experiments, is
> the value of .1 too small to bother with? CP caps are long as opposed
> to NWL's square, so applying that current to a small inductance would be
> harder
> due to the added inductance of runs from the cap to whatever.

These caps can be used for discharge work in exploding wires, but a large 
cap 1uf or larger would be better for that service.
  I prefer 2uf. - R. Hull
> All my figureing is based on using these caps in 4 configureations that will
> be used in the future.
> 1). 80 khz, 2 x .1 balanced, l= 89uhy, zsurge=42, peak amps=673,
> rms amps (20%)= 134
> 2). 80 khz, 1 x .1 unbalanced, l= 43uhy, zsurge=20, peak amps=1415,
> rms amps (20%)= 283
> 3).150 khz, 1 x .1 unbalanced, l=31uhy, zsurge=24, peak amps=1179,
> rms amps (20%)= 235 (guess I could put 2 in series & change inductance,
> then again I would like to compare configureations myself)
> 4). 50khz, 2 x .1 (parallel) unbalanced, l=56uhy, zsurge=16, peak amps=1768
> rms amps (20%)= 353
> CP caps eng figured that a 130khz circuit would draw 110 amps rms (he did
> quite a bit of calculating, that at times I must admit was over my head)
> What input do you guys have on all of my ramblings so far?
> Kevin M. Conkey

Kevin I have answered above in the body of the text.  I think that yo are 
probably over concerned and maybe even stuck on points of little relative 
merit.  I believe either company will get you a cap which will serv you 

Richard Hull, TCBOR