From: Alfred A. Skrocki [SMTP:alfred.skrocki-at-cybernetworking-dot-com]
Sent: Saturday, February 07, 1998 7:56 AM
To: Tesla List
Subject: Re: Voltage/Length (fwd)
On Thursday, February 05, 1998 6:17 AM Greg Leyh
> John H. Couture wrote:
> > It should be noted that using the equation
> > Vs = Vp sqrt(Cp/Cs)
> > can give incorrect results when applied to Tesla coils.
> > If the Cs is reduced in the above equation (reduce toroid size) with no
> > other changes the Vs and sparks can be shown to be greatly increased. We
> > know this is not true because it is contrary to tests of real coils.
The above is wrong because it does not consider the fact that the
equation Vs = Vp sqrt(Cp/Cs) refers to the distributed or parallel
secondary capacitance. The toroidal capacitance is in SERIES with the
secondary and actually decreases the total secondary capacitance and
this is why adding a toroid usually increases a coils output.
Ctotal = 1/(1/Csecondary + 1/Ctoroid)
yet it's own capacitance holds the necessary energy for increased output.
> But Vs isn't the the only factor that affects spark length!
> Real world factors, such as break rate and terminal capacitance
> both _dramatically_ affect spark length, independent of Vs.
This is definitely true! All these factors influence the efficiency
of the coil.
> When you increase the toroid size and see longer sparks,
> Vs has actually _decreased_, but the coils' effectiveness
> at propagating the spark channel has improved by an even
> greater amount, due to bigger toroid's improved capacity
> to provide fast currents to the base of the spark.
That's not really true for the reason I explained above.
> The equation Vs = Vp sqrt(Cp/Cs) follows directly from
> Conservation of Energy, and simply sets an _upper limit_
> for Vs. It's true that Vs can drop below this amount
> if the coil is inefficient, but Vs can never be _larger_
> than this quantity.
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Alfred A. Skrocki
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