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Re: Barts Coil Desing (was flashing vs. whatever)


From: 	Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
Reply To: 	bert.hickman-at-aquila-dot-com
Sent: 	Sunday, November 30, 1997 12:49 AM
To: 	Tesla List
Subject: 	Re: Barts Coil Desing (was flashing vs. whatever)

Tesla List wrote:
> 
> From:   Barton B. Anderson[SMTP:mopar-at-mn.uswest-dot-net]
> Sent:   Saturday, November 29, 1997 11:01 PM
> To:     Tesla List
> Subject:        Re: Barts Coil Desing (was flashing vs. whatever)
> 
> Bert,
> 
> > <SNIP>
> > NOW I understand the source of the discrepency! It is essential that
> > your tank cap and primary be tuned to your secondary/toroid's operating
> > frequency. Now, for maximum power output you may also choose to "size"
> > the tank cap to the transformer/ballast power delivery capability.
> > However, you must STILL keep the system in tune. BTW, the 14.4 KV term
> > in the above equation is already RMS volts, so it does not need to be
> > derated by 0.707. This results in a properly "sized" cap value of about
> > 0.128 uF to match 10 KVA. However, you can easily run the pig
> > intermittently at 20 KVA which will bring you up to the 0.256 uF cap
> > previously computed.
> >
> > However, when you increase the size of the tank cap, you also directly
> > increase the amount of energy per "bang". Going from 0.05 uF to 0.256 uF
> > basically quintuples the energy available when the gap fires. For
> > example, if your gap fires at 16 KV, you'll have 6.4 Joules of energy
> > per bang with a 0.05 uF cap, but a whopping 32.7 Joules with the 0.256
> > uF cap. All other things being the same, the output voltage of the coil
> > would also increase by a factor of about SQRT(5) or 2.24 times...
> >
> 
> Ok, Now I understand my discrepancy. Thanks! I knew the KVA rating of the pole pig is
> rated as "apparent power" due to inductive loading, but I didn't know the output voltage
> was rms. I went back through the calcs and came up with 0.128uF (as you did) equating to a
> needed reactance af 12.44ohms. This would eventually work out to 16.4 Joules. What do you
> think, is this still a bit too "Whopping" for the 12.5" x 33.2" Secondary? I definitely
> want to throw as much "umph" at the coil that it can electrically handle, but then I don't
> want to kill it (at least on the first couple firings). It might be wise to just go off
> the 0.05uF and modify the primary to match Xc?
> 
> Let me know your thoughts,
> Bart

Bart, 

This is about the minimal length coil for a 0.05 uF tank cap driven off
a 14.4 KV source. This coil should be deliver 8-9 foot streamers, which
would be about 3X your secondary coil-length. While you can do quite
alot to shape the E-Field at the top of the coil by using a larger
diameter toroid, it's still very difficult to prevent most of your
strikes from going between the toroid and the strike-ring when your
streamer length gets much above 2.5-3X your coil length. I'd go with a
single 0.05 uF cap for now. If you decide later on that you'd like to
bump the power level up, you can add another 0.05 uF cap in parallel
with the first and "grow" the other parts of the system to match...

Safe coilin' to you, Bart!

-- Bert --