Re: Bart's Coil

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "John H. Couture by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
> 
> Antonio -
> 
> If I understand the relations you show below the a and b values cannot be
> determined at the design stage but only by tests after the TC is built. Is
> this correct?

You can determine a and b by looking at the waveforms after the coil is
built, but can also choose them at the design stage, designing a coil
with previously known resonances and energy transfer time, and perfect
energy transfer. 
Choose a and b as two integers with odd difference and a base frequency
f0 (Hz), and then compute L2*C2 , L1*C1, and k12 from the formulas:
f0=(1/(2*pi*a*b))*sqrt((a^2+b^2)/(2*L2*C2))
L1*C1=L2*C2
k12=(b^2-a^2)/(b^2+a^2)
Choose one of the elements (L2, C2, C1, or L1), and add the condition 
for maximum output voltage to get the others:
Voutmax=Vinmax*sqrt(C1/C2)
Maybe more practical to measure the resonance frequency of a built 
secondary with terminal, obtaining L2*C2 from the frequency (f2)
instead of choosing f0:
f2=1/(2*pi*sqrt(L2*C2))
Build then a coil that satisfies these relations.
 
> Have you tested your coils for K factor and if so what were the results?

The coils that I have built (only low-power tests so far...) were
designed in this way, and behaved accordingly. Losses and high-order
effects decrease the maximum output voltage a bit and add a decay in 
the waveforms, but the frequencies and the energy transfer time do not 
deviate much from the ideal design values.

Antonio Carlos M. de Queiroz