Re: Primary Coil Design
>>From MSR7-at-PO.CWRU.EDU Thu Mar 28 11:13 MST 1996
> For close-wound secondaries this is another matter. There appears
>to be a net reduction in proximity effect for close-wound secondaries due
>the presence of a large toroid above a helical resonator.
> What appears to be happening is that the electric field produced
>by the toroid reduces proximity effects in the coil, thereby raising the Q
>of the secondary. This is probably due to the linearization of the 1/4
>voltage rise. What I mean by this is that the capacitive top hat reduces
>the phase angle by which the secondary must operate at to achieve 1/4 wave
>resonance. We need 90 degrees of phase shift for 1/4 wave, but the toroid
>reduces this to perhaps 50-60 degrees along the coil, if a large toroid is
>employed to make up the difference.
A thought occurred to me while reading this thread. The toroid
acts like a shorted turn, N inches above the primary, this decouples
the top portion of the secondary,from the primary, and allows it to
act as a magnifier coil.
>. This means that the overall
>secondary Q is higher, and that losses are reduced. The energy storage of
>larger capacitance (E=1/2 x C x V^2) seems to promote more energetic
>breakout as well.
The spark acts as a low Z shunt, since P=I^2 * Z, shunting an
inductance (secondary coil) does not produce the large current need
for high power, energetic, sparks. The C of the toroid, however, does
provide this when it is shunted with a low Z.