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Re: TC Secondary Terminal Design
Have you tested this by changing the voltage, and measuring the change?
Where did you get the equations?
James.
>Original Poster: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
>
>
> All -
>
> Finding the proper size secondary terminal has now become easier when
>using a new(?) equation that I have derived from several theoretical
>equations. This is not a precise solution but does get you a ballpark
figure.
>
> The sizing of the secondary terminal capacitance is part of the tuning
>process and must satisfy the Lp Cp = Ls Cs equation. However, the size is
>also determined by the input voltage and wattage. When the input voltage or
>wattage is increased the secondary terminal capacitance should be
increased.
>
> The equation I derived to do this is as follows:
>
> Cs = 12.34 * cuberoot(KVp^2 * Cp)
>
> Cs in pf Cp in uf
>
> Note that Cs in this equation is based on input voltage and also on the
>input wattage when
> Cp = J/Vp^2 and J = Input watts/ Breaks per second
>
> The equation is derived assuming the following:
>
> The secondary terminal is a sphere and
>
> Cs (pf) = sphere dia * 1.41
>
> Secondary kilovolts = sphere dia * 32.5
>
> Sphere breakout is 65 KV per inch radius
>
> KVs = KVp * sqrt(Cp/Cs)
>
> When the secondary capacitance is found the approx. sphere dia can be
>found by subtracting the sec coil self cap from the secondary capacitance.
>
>-------------------------------------
>
> EXAMPLE -
>
> Given Primary volts 15 KV rms * 1.4 = 21 KV peak
> Primary wattage 1000
> Breaks per second 120
>
> Find Primary capacitance Cp
> Secondary capacitance Cs
>
> Watts per break = 1000/120 = 8.33
> Cp = 8.33/21^2 = .019 uf
> Cs = 12.34 * cuberoot(21^2 * .019) = 25 pf
>
> Sec volts = KVs = 21 * sqrt(.019/25*10^-6) = 579 KV
> Sphere dia = 579/32.5 = 17.8 inches
>
> For a check use Cs = sphere dia * 1.41
> = 17.8 * 1.41 = 25 pf as above.
>
>-------------------------------------
>
> This gives the approx. secondary terminal size when it is a sphere. The
>equations would have to be modified for a toroid. Does anyone want to give
>this a try?
>
> Note that the Cp/Cs ratio is important because it fixes the Ls/Lp
>inductance ratio. You only have to decide on the secondary inductance or
>the primary inductance. The operating frequency can be found by
> F = 1/(6.283 * sqrt(L * C))
>
> Note also that this explains the apparent dilemma in the equation
> KVs = KVp * sqrt(Cp/Cs) that indicates the secondary capacitance (Cs)
>should be made very small to obtain a large secondary voltage.
>
> I would be interested in comments from coilers on this somewhat novel way
>to find the secondary terminal size.
>
> I am obliged to make the following comment - the above can be more easily
>implemented using the JHCTES computer program. Please forgive.
>
> John Couture
>
>--------------------------------
>
>