Re: larger OR smaller than resonant ??? (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: List moderator <mod1@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Fri, 1 Jun 2007 17:14:10 +0100
From: James Howells <james@xxxxxxxxxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: larger  OR smaller than  resonant  ???

I am building my first NST tesla and have several options of Capacitors to 
use however,
But I have a dilemma I could do with some advice on

The NST has a natural frequency of 18nF  and the capacitors I have will give 
me either

15-16 nF, 18nF or about  60 nF
I have learned about 1.5 X Nat Frequency is best ( LTF) so I need about 27 
nF

But I can remember some discussion on Smaller than  resonant frequency also 
being acceptable ... should I go for the 15nF combination ?


( the spec on the NST is a little strange ... 3000 E 3000
37 /52mA    127 W )





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----- Original Message ----- 
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, June 01, 2007 4:43 PM
Subject: RE: larger than resonant (fwd)


> Original poster: List moderator <mod1@xxxxxxxxxx>
>
>
>
> ---------- Forwarded message ----------
> Date: Fri, 1 Jun 2007 10:55:09 -0400
> From: "Lau, Gary" <Gary.Lau@xxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: RE: larger than resonant (fwd)
>
> There are actually two reasons to use an LTR cap over a mains-resonant
> cap.
>
> The most frequently cited reason is that should you open your static gap
> too wide, a mains-resonant cap will resonate at 60 Hz with the NST
> secondary and "ring_up", to whatever breakdown voltage your gap is set
> to.  If your gap is set to break down at 50kV, it will get there, unless
> your NST or your cap break down and smoke first :-(
>
> Using an LTR cap shifts the NST/cap resonant frequency away from the
> mains-frequency, although it will still see some resonant-rise at 60 Hz.
> If it did not, your gap would never fire if the variac was less than
> 100%.
>
> A less often acknowledged reason to use LTR is that maximum streamer
> length correlates to bang size - 1/2 * C * Vgap.  With the same gap
> breakdown voltage (cap charging or bang voltage), a larger capacitance
> will yield a larger bang and result in a longer streamer, even if the
> BPS rate is less.  Of course the lower BPS rate will make for a less
> white-hot and impressive streamer - it's your choice.
>
> Regards, Gary Lau
> MA, USA
>
>> Date: Fri, 01 Jun 2007 05:54:39 -0400
>> From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
>> To: tesla@xxxxxxxxxx
>> Subject: larger than resonant
>>
>> Hey everybody,
>>      Can somebody explain to me the advantage to using a "resonant" or
>> "larger than resonant" tank capacitance?  I seen coils get huge sparks
> using
>> LTR and also very small tank capacitors, so what is the point?
> Thanks.
>> Scott Bogard.
>
>
>
>