Re: The 1500t secondary myth

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Dr. Resonance" <resonance@xxxxxxxxxx>


It's not a myth --- it's physics, pure and simple.

The potential developed across an inductor is V = -L di/dt.

It is very apparent that the larger the inductance, the large the output
potential (assuming similar values for the rate change of current across the
inductor).

Since inductance, L, is dependent on the physical geometry of the inductor
and the number of turns on the inductor, the greater the number of turns the
larger the potential.

Balanced against this is the resistance of the wire which, beyond a certain
point, impedes resonance.

I have tested literally hundreds of coils and always found 1,200 to 1,500
turns to be an optimum point for most coils in the 1 kVA to 15 kVA range.
We start out most designs by (1) after selecting a diameter suitable for the
power level, then determining the 4.5:1 height to dia. ratio, and then (2)
dividing this winding length by 1,400 to determine the correct number of
turns.  This produces a fixed wire dia. to use for the winding.  We always
use 200 degree C wire due to its increased insulation value and tough
finish.

Resonance and current factors become more deterministic above the 12-15 kVA
range where larger dia wires to carry the high peak currents become
necessary.

Dr. Resonance

Resonance Research Corporation
E11870 Shadylane Rd.
Baraboo   WI   53913
>
> I think we've always known there was a good bit of
> leeway, but a larger body of tests (some performed
> with rigorous standards) have been performed by
> coilers in the US and Europe, which support a
> 1000-1600T secondary.  See the pupman archives.  I
> wouldn't be so quick to call the 1500T secondary a
> myth without a larger body of evidence to back up your
> claims.
>
> Talk to you later.
>
> -Brett
>
>
> --- Tesla list <tesla@xxxxxxxxxx> wrote:
>
>  > Original poster: "Tom Luttrell PWRCOM"
>  > <tom@xxxxxxxxxxxxx>
>  >
>  > I finally got around to testing my latest TC set up.
>  > Due to a
>  > transportation accident that destroyed my old
>  > secondary coil I changed
>  > the configuration from 750t with an NST resonant
>  > primary cap to a 1200t
>  > secondary with an LTR primary cap. Both secondary
>  > coils have about a
>  > 4.5:1 aspect ratio.
>  >
>  > This has produced no noticeable change in the output
>  > spark length (still
>  > around 950mm for NST faceplate value of 880VA).
>  >
>  > There seems to be a large amount of leeway in the
>  > accepted wisdom of
>  > using a 1500 turn secondary.
>  >
>  > I do however feel a bit better about running my NST
>  > with an LTR cap, and
>  > also now having a flat pancake primary coil and
>  > adjustable height
>  > secondary has solved my over coupling racing spark
>  > problem.
>  >
>  > Tom.
>  >
>  >
>  >
>
>
>