Re: bang power ? (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 27 Sep 2007 10:08:29 -0500
From: Bert Hickman <bert.hickman@xxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: bang power ? (fwd)

Tesla list wrote:
> ---------- Forwarded message ----------
> Date: Thu, 27 Sep 2007 10:44:54 +0100
> From: Chris Swinson <list@xxxxxxxxxxxxxxxxxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: bang power ?
> 
> Hi all,
> 
> Just wondering, if you progress from say 10nF to 20nF, does it actually make 
> the bang power more, or does it sustain the charge longer so it takes longer 
> to ring down ?
> 
> Cheers,
> Chris 
> 
> 
> 
> 

Hi Chris,

If everything else stayed the same (which it rarely does), and you 
substituted a 20 nF cap into the same system, the primary bang energy 
(in joules, or watt-seconds) would double when going from a 10nF to a 20 
nF tank cap. BTW, there is no such thing as "bang power", only "bang 
energy". You can estimate tank circuit power by multiplying the number 
of bangs per second (main gap break rate) times the energy per bang 
(0.5*Cp*(Vp^2)), since this gives you power (in watts):

Primary Power = BPS * Bang Size

The above discussion assumes that you can indeed charge the 20 nF tank 
caps to the same voltage as the 10 nF cap to fire the spark gap. 
Depending on how much current the HV transformer can deliver, your break 
rate may be significantly reduced, or the transformer may not even be 
able to charge the larger cap sufficiently to fire the gap. We'll 
"assume" that the gap can fire in both cases.

Further, if we assume you use the same primary inductance, the resonant 
frequency of your primary tank circuit will decrease by a factor of 
1/sqrt(2). So, if your original primary resonant frequency was 100 kHz 
using a 10 nF cap, the new resonant frequency will become F1/1.414 or 
about 70.7 kHz. If the previous system was "in tune" with the secondary 
using a 10 nF cap, in order to bring the system back into tune using a 
20 nF cap, you'll need to reduce the primary inductance to one-half of 
its previous value.

But, if you reduce the primary inductance (say, by changing the tap 
point) this also alters the P-S coupling unless you ALSO change the 
primary-secondary geometric relationship. And, as we discussed earlier, 
changing the coupling alters the "ring-up" time (the time to complete a 
single P->S or S->P energy transfer).

That's why I said that all things seldom stay the same when you try to 
change just one parameter in a coil...  :^)

Bert
-- 
***************************************************
We specialize in UNIQUE items! Coins shrunk by huge
magnetic fields, Lichtenberg Figures (our "Captured
Lightning") and out of print technical Books. Visit
Stoneridge Engineering at http://www.teslamania.com
***************************************************