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Re: Could anybody PLEASE help me???

Hi Sam,
	Here is my shot at you questions...

At 01:04 PM 9/18/98 PDT, you wrote:
> Hi!
>
> This is the second time I am posting this message. Last time no one 
>replied and I haven't made any progress since than on my Coil. Since the 
>answers to these questions are vital to my progress, I urge anyone with 
>the time and knowledge to answer this to do so...

Sometimes we all get wrapped up in or lives and don't get time to respond
to stuff we would like to....

>
> ---Sorry for the long message, but PLEASE read on---
>
> Ok. My design aims for a medium power, very reliable, as efficient as 
>possible, good-looking Tesla Coil. I'll be tapping its energy to conduct 
>electromagnetic repulsion, confinement and acceleration of plasma, so 
>ground strikes shouldn't be much of a problem.
> The main thing I am looking for here is efficiency. I want this coil to 
>be as efficient as possible. Therefore I've given it a 3:1 H/D ratio and 
>an angled primary, together with the use of  0.60 (between AWG 23 and 
>22) wire (any thicker would be seriously wasted by "skin effect")
> Well, here are the specs for my coil so far:
>
> Secondary:
>
> Coil form:
> Diameter: 20cm (8in)
> Winding Length: 60 cm (24in)
> Total length from toroid bottom to secondary bottom: 80cm (32in)
> Wire gauge: 0.60mm (between 23 and 22AWG)
> Spacing between turns: NONE
> Secondary turns: 1000
> Secondary wire length: 627.69m (2028.57FT)
> Approximate resonant frequency: 186.11KHz
> Secondary quarter wavelength resonant frequency: 119.49KHz
> Secondary self-capacitance: 12.84pF
> Toroid capacitance required to form quarter wavelength coil: 18.31pF
>

I assume you have used all the standard equations and such.  The quarter
wavelength stuff has been disproved but in your case it won't hurt anything
if you use it.


> Primary:
>
> Primary capacitance: 0.0127uF
> Primary resonant frequency: 119.49KHz
> Primary conductor diameter: 8mm (0.320in)
> Primary turn to turn spacing: 8mm (0.320in)
> Spacing between the secondary and inside turn of primary: 55mm (2.2in)
> Primary tapped between turn 14 and 15 to form a resonant circuit at 
>119.49KHz
>
> Neon transformer/Capacitor matching (not decided yet):
>
> Transformer input voltage: 220V
> Transformer output voltage: 15KV
> Transformer operating frequency: 50Hz
> Transformer output current: 60mA
>

Sounds fine.  A 0.0127uF cap and a 60mA neon will be able to over voltage.
Be sure to use safety gaps to protect the neon from over voltage burn out.

> Ok. Now the problems begin:
>
>1- I have 2 ferrite cores, such as those used in radios. They measure 14 
>x 1cm (5.6 x 0.4in) and I also have 60 meters of 0.60mm (AWG 23/22)wire, 
>left from the Coil. Can I wind 2 good chokes using them? Would I need 
>more? I can get more of them, or a different wire, but no different 
>ferrite cores. How much inductance would be ideal for my coil? I think 
>2mH should do, but I could be wrong...

The ferrites are too small to be of much use.  Personally I always use
resistors and capacitors for the protection circuit.  I'll leave the use of
inductors to people more expert than I in their use.

>
>2- Mike Hammer suggested I used the following primary: 18 turns of 8mm 
>(0.320in) thick copper tubing spaced 8mm (0.320in) from each other, and 
>with 3cm (1.2in) clearance from the secondary and a 15 degrees angle. I 
>agree that's a better option, but I am not sure if it's the best option. 
>I feel I can make the secondary/primary clearance less. Perhaps 0.5in if 
>I insulate the primary (the secondary is already very well insulated 
>with epoxy and PU sealer). And, such a primary would have a diameter of 
>about 80cm (32in). That's HUGE!!! It would need such a massive base. Is 
>that really the best configuration, or can I make the primary coil 
>smaller and therefore increase inductance? I want the most efficient 
>design, remember!
>

I would space it by at least an inch.  If it arcs, it can do serious damage
to the secondary.  Mike knows what he is doing and I would follow his
advice.  You could make the primary smaller with the same results but it
would be harder to make and require some heavy computer calculations.

> One idea I had was giving the turns some 1mm spacing, and having 2 cm 
>clearance from the primary to the secondary. I would than insulate the 
>space between the turns and between primary and secondary with 
>Plexiglas, and also insulate the top of the primary and the bottom of 
>the toroid with Plexiglas. Would this work? Would it be a more efficient 
>coil? What is the ideal primary for my secondary, using power levels 
>between 1 and maybe 3KW?

I think a coupling of around 0.2 would be right for your coil.....  You
should be able to get this easily without having to go to any extremes.
Very high coupling won't improve performance but will hurt it.  Mike's
suggested primary sure sounds just right to me.

>
>3- Here in Holland the largest transformers available (because of legal 
>restrictions) are rated 8KV/50mA. I've being to all 13 Neon Shops within 
>a 50 KM range (it took me 5 days) and NOT A SINGLE ONE OF THE WILL GIVE 
>OR SELL ME A USED TRANSFORMER. Let alone the 3 I would need to run my 
>coil. A single new transformer here costs 300 dollars (rated 10KV, 
>100mA. They come from Italy and are impossible to get without and order)
> Can some kind soul sell me a 1000W+ working, used neon transformer? 
>PLEASE!!! I really need this, and there is no other way I can get it.. I 
>can pay some 25 dollars plus the costs of transportation

They are heavy!  Probably have to have someone in Europe get you one.  Too
expensive to ship from the states.  Look into microwave transformers.
Soooo....  You can't get a neon in Holland but the grocery stores sell
marijuana... hmmmm :-))

>
> Thank you very much for taking your time and reading such a long 
>message (supposing you didn't just scroll down looking for the "delete" 
>button). Please help me if you can... Any questions, comments, hints are 
>very welcome.
>
> THANKS!!!!
>
> Sam Barros
>
>

	Terry