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Re: Information Unlimited BTC30 coil

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Jay,

Terry put together a pdf file called "Formula's for Tesla Coils". There's a copy at his site "hotstreamer.com" and at my own site which should help with some of those formula's.


You should also use a program as the basic formula's are standalone calcs (but important to know and understand). I ran a quick calc on your coil with JAVATC just now. I'll paste results below. Although there is some info on the secondary, the rest is just a guess based on pics. JAVATC is a design program, so perfect for using with the BTC coil.


If you have any questions on the program, just email me off list (no need to clog up the list with that kind of stuff). I also inserted some text info next to each input so that it makes some sense to you.

Take care,

Friday, January 05, 2007 05:38:36 PM

Units = Inches
Ambient Temp = 68°F

Surrounding Inputs:
100 = Ground Plane Radius = Radius of floor the coil would be in. I didn't include any other surroundings.
0 = Wall Radius
0 = Wall Height
0 = Ceiling Radius
0 = Ceiling Height

Secondary Coil Inputs:
Current Profile = G.PROFILE_LOADED
1.75 = Radius 1 = Radius of the lower end of secondary
1.75 = Radius 2 = Radius of the upper end of secondary
20 = Height 1 = Height above ground of the lower end of secondary
29.75 = Height 2 = Height above ground of the upper end of secondary
430 = Turns = I calc'd the turns for you based on 9.75" length secondary
24 = Wire Awg

Primary Coil Inputs:
2.5 = Radius 1 = Inside radius of flat primary (I guessed at a 5" diameter)
5 = Radius 2 = Outside radius of flat primary (what would equal 5 turns)
20 = Height 1 = Height of inside radius (I set flat primary even with bottom of secondary)
20 = Height 2 = Height of outside radius (obviously the same for a flat coil)
5 = Turns
0.25 = Wire Diameter
0.006 = Primary Cap (uF) = Cap size close to what is need for this coil
30 = Total Lead Length = I assumed about 15" of lead wire from each end of primary coil
0.2 = Lead Diameter = I assumed a diameter of conductor

Top Load Inputs:
Toroid #1: minor=1, major=6, height=31.5, topload = I guessed at the toroid
Disc #1: inside=0, outside=5, height=31.5, topload = This is the inside disc of the toroid

Secondary Outputs:
793.13 kHz = Secondary Resonant Frequency
90 deg° = Angle of Secondary
9.75 inch = Length of Winding
44.1 inch = Turns Per Unit
0.00257 inch = Space Between Turns (edge to edge)
394 ft = Length of Wire
2.79:1 = H/D Aspect Ratio
10.11 ohms = DC Resistance
23522 ohms = Forward Transfer Impedance
23260 ohms = Reactance at Resonance
0.48 lbs = Weight of Wire
4.668 mH = Les-Effective Series Inductance
4.383 mH = Lee-Equivalent Energy Inductance
5.014 mH = Ldc-Low Frequency Inductance
8.627 pF = Ces-Effective Shunt Capacitance
7.922 pF = Cee-Equivalent Energy Capacitance
16.447 pF = Cdc-Low Frequency Capacitance
3.3 mils = Skin Depth
4.617 pF = Topload Effective Capacitance
72 ohms = Effective AC Resistance
323 = Q

Primary Outputs:
785.54 kHz = Primary Resonant Frequency
0.96 % high = Percent Detuned
0 deg° = Angle of Primary
9.82 ft = Length of Wire
0.25 inch = Average spacing between turns (edge to edge)
0.75 inch = Primary to Secondary Clearance
5.98 µH = Ldc-Low Frequency Inductance
0.00589 µF = Cap size needed with Primary L (reference)
0.861 µH = Lead Length Inductance
31.364 µH = Lm-Mutual Inductance
0.181 k = Coupling Coefficient
5.52  = Number of half cycles for energy transfer at K
3.44 µs = Time for total energy transfer (ideal quench time)

Tesla list wrote:

Original poster: jhowson4@xxxxxxxxxxx

Oh yea I'm Jay by the way             hey that rhymes

Well he did not buy the kit you see. It was left in the closet thing from the previous teacher and he did not know what to do with it so he stuffed it back in the closet then I found it and asked if I could have it so after thinking it over for like a month he gave it to me. YAY

The secondary has a 3.5in diameter and the wire section is 9.75in tall and has 24 gauge wire. I made the primary but it is weird. There is a big hole with 6 turns of 12gauge wire that are bunched together then that wire goes into 4 turns of small copper tubing.
How do I calculate the inductance for that?
I did not trim the copper tubing yet I will do that after I am done I guess.
The RF filter is 24 turns of 24 gauge wire

I put together the spark gap, capacitor and the weird case thing.

-------------- Original message --------------
From: "Tesla list" <tesla@xxxxxxxxxx>

> Original poster: Mike
> I don't know your name, but hi.
> It was cool of your teacher to give you this kit to
> build. It sort of detracts from your education on the design
> aspect, but hey....if he is willing to fork out too much $$ (based on
> my awesome scavenging skills lol) to further your education....I'm
> all for it. There's no substitute for winding your own
> secondaries...and I'd replace that filter choke with a 'Terry filter'
> as soon as you can. Another improvement would be to add an
> additional spark gap or two.....AFTER you get it going. Just that
> for a static gap system, a few gaps in series will quench
> better. You didn't mention the wire guage used on t he sec ondary,
> so I will have to make some assumptions for the moment. It would
> seem that there is a possibility of tweaking this system......but
> build it as is for now.
> Original poster: jhowson4@xxxxxxxxxxx
> Hello All
> 2nd day back to school and I am still on break.=)
> My Physics teacher gave me the BTC3 kit today. YAY
> So here are pictures of what it comes with.
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