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SPICE, Solid State Suk's, and Slugs (fwd)


From: 	Alan Sharp[SMTP:100624.504-at-compuserve-dot-com]
Sent: 	Monday, December 22, 1997 3:53 AM
To: 	INTERNET:tesla-at-pupman-dot-com
Subject: 	SPICE, Solid State Suk's, and Slugs (fwd)

Scott,

I was very interested in your post.

My maximum spark is 14 inches from Solid State electronics - the
details are on my web site.

  http://ourworld-dot-compuserve-dot-com/homepages/AlanSharp

The bottom feeding magnifier arrangement means the energy can be
put in over say 10mS.  

Looking at your options:

>1) Building a switch-mode inverter to turn 120VAC to 20KV+, since the size
>of the primary discharge capacitance decreases with the square of the
>voltage, and it's dielectric thickness increases linearly with voltage,
why
>not use 100KV+ in spark gaps? This would make for a very compact and
>effiecent supply, that could be shut down after the gap fires, for rapid
>quenching

But the Ferrite cores commonly available are physicaly small with very
limited
winding areas - how will you fit in the amount of insulation that will be
reduced
for 20KV+ - or even 10KV. You'll also need a big step up ratio on the
transformer
but then interwinding capacitance becomes a problem.

>2) Use massive array's of semis. Too expensive. Too many tears over the
high
>body count.

Mark Barton did this for his 3 foot "sheets of flame " coil - it did end in
tears.

>3) This option I am pursuing now. Slug my secondary with ferrite. Bring
its
>resonance down to 25KHz. Increase it's time constant to 10milli-seconds.
Now
>I have time to put 50J of energy into it using semi's. My problem will be
>dielectric heating and loss of all the poly I'll be using around the
slugs.
>Hopefully, the slugs I have (giant beads, 2"x2"dia with 3/4"hole) won't
>saturate in a 5"dia coil, bring its inductance up from around 45mH to over
>1H, and not have horrible core loss. My Q better be 750+. More simulations
>to do.

Mark Bartons solution was wind a coil the size of a oil drum.
I found a big improvement on increasing the inductance of my coil. But this
means that coils have to be physicaly bigger or have more turns of
thinner wire - more resistance. 
Slugging the coil with Ferrite is very attractive but the snags are the
ones
you mention plus internal sparking to the slug. We may just trade one set
of losses for another. It maybe that a modest bit of slugging at the
bottom of the core could be helpful.

>I know, its not a Tesla Coil, its probably a Oudin coil. But it will make
>4'+ sparks, and quite a show. Its low frequency skin depth will probably
>blow the surface layers clean off anything it zaps.
>Has anyone made a study of exploding fruit/veggies?

Or exploding fingers - even 6 feet away from my 500W coil - I can get
sparks jumping from my fingers to the metal.

>Comments anyone? Has anyone built a semi-coil that put out sparks over
1-1/2'?

Not yet but I think the way to do it is to build two identical coils and
drivers - out of
phase.

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