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Re: more turns or biger cap?



Original poster: "Stephen Conner by way of Terry Fritz <teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>

At 10:49 14/06/03 -0600, you wrote:
>Original poster: "J Dow by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
><jdowphotography-at-hotmail-dot-com>
>
>Hello all
>Thanks for identifying that ebay thing.
>
>After a coiling for a few years and with John Freau's TC efficiency theory.
>It seams that the best performing coil is a large one 1600 turns of thin 
>wire and a primary with many turns.
>But this means that the cap wants to be small.
>If I'm running a coil with a 5kw 4-pack MOT stack, the cap can be big, and 
>should be to handle the powers involved. So does this point to an even 
>larger coil to get the beast performance?

You can run high powers with a small capacitor if you use a high charging 
voltage. Of course, too high and you'll have trouble with things flashing 
over etc. DC coils with voltage multipliers, secondary-side inductive 
ballasts, etc. are all ways of boosting the charging voltage.

You can also run high power by increasing the bps, but this tends to make 
the sparks thicker and brighter rather than longer. John Freau's spark 
length formula is for cois running at 120bps so a higher bps unit will tend 
to underperform. However, it may look and sound a lot more spectacular :)

For instance, I built a medium sized DC coil with a 1200 turn 3.5" x 20" 
secondary, 13 turn primary, 9.4nF cap, and charging voltage of 20kV. The 
RSG was made from a couple of brass screws attached to a vacuum cleaner 
motor. Performance is 31" at 500bps.

Had I gone for 120bps operation, I would have needed a cap more than 4 
times the size, and correspondingly fewer primary turns. I might have got 
48" this way. That is more than twice the length of the secondary, so it 
would probably have self-destructed.

Fellow UK coiler Dave Gamble has a similar DC setup but much bigger and 
with 40kV charging voltage. It produces arcs over 6 feet using a 50nF cap, 
but things tend to flash over and go on fire.

Steve C.

http://www.scopeboy-dot-com/tesla/