Re: Tesla coil formulas

["Tesla list" <tesla@xxxxxxxxxx>]

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

Hi Terry,

Excellent! Glad to see you doing this. Matt's page was certainly a 
valuable resource, especially for new coilers. Programs are nice, but 
I think it is important to do math on paper now and then. It keeps 
the senses sharp for engineers and is overall helpful for new coilers.

For the primary inductance you list well known equations for helical 
and flat spirals. The conical equation is not listed. Probably best, 
because the classical conical equation was never true to measurement. 
I did work out a modification to this equation prior to Paul's 
ability to solve conical inductance's, and it fares pretty well with 
all possibilities (flat, cone, and helical).

The equation used was L = sqrt((L1*Sin(X1))^2 + (L2*cos(X2))^2)

L1 = ((W^2) * (N^2)) / ((9*W) + (10*h))
L2 = ((W^2) * (N^2)) / ((8*W) + (11*w))
X1 = COS(RADIANS(angle))
X2 = SIN(RADIANS(angle))
N = turns
Z = N * (WireD + Spacing)
h = Z * SIN(RADIANS(angle))
w = Z * COS(RADIANS(angle))
R = Inner Diam. / 2
W = R + (w / 2)

Input data is then: Angle, Inner Diameter, Turns, Wire Diameter, 
Spacing (edge-edge).
There is certainly Bart-ism here, but it did serve well in early 
programs for all primary coils. This may be something you want to add 
(or not). Thought I'd throw it out there.

You have the basic info which is great! There are obviously many 
equations for each topic (energy, inductance, etc..). I'm not sure if 
you want to include the others or not, that's up to you.

Something else which is often thought about but not calc'd is primary 
surge impedance.
Surge Impedance = sqrt(Lp/Cp) = the higher, the better (higher = 
lower gap losses).

For PFC, John Cortures, I use:
(KVA*10^9)/(2*pi*F*Vin^2)
But, all PFC calc's are really ballpark. Always best is trial and 
error. "Equation is a starting point".
Short commentary would be meaningful for new coilers.

For BPS-Power (energy), BPS = .5 * Cp * eVp^2
Where
eVp = Vp*(1-e^(-t/zc)
e = 2.7182818
-t = 1/bps*1000
zc = transformer Z*Cp
This equation pulls in charge time, thus a more accurate 
representation of voltage at the cap. eVp is certainly important 
here. The only other way is measurement (which is always best).

Well, I realize the basics are really what is important. I commend 
you for this write up. I think this type of info is great for new 
coilers and even the old timers who have become complacent with 
programs. Man, you could really fill this page with all kinds of 
stuff, but I'm not sure that is a good idea.

Bart


Tesla list wrote:

> Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>
>
> Hi All,
>
> I used Matt Behrand's Tesla coil formula page a lot.  It kept 
> getting shutdown for too many hits and now it seems gone permanently :-((
>
> http://home.earthlink.net/~electronxlc/formulas.html
>
> So, I guess I will have to make one myself :-))
>
> Here is what I have so far:
>
> http://hot-streamer.com/temp/FormulasForTeslaCoils-100.pdf
>
> I can make it into a web page when it gets more polished.  I just 
> threw it together tonight mostly from memory, so beware it might be 
> all wrong at this point %:o))
>
> If anyone has any suggestions or things they want added just let me 
> know.  I realize that I might be the last person on Earth who still 
> figures it all out by hand ;-)))
>
> Cheers,
>
>     Terry
>
> Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>