Dear Paul,
Thank you for your concise explanation.
I forgot that adding a topload lowers the resonant frequency of the coil.
So there is no way to match the topload to the secondary. Tuning is done on
the primary side.
A follow up question: are the primary and secondary oscillating at the same
frequency or at a 1/4 wavelength?
I get confused because I often see the 1/4 wave mentioned. JavaTC seems to
supply numbers for a matched resonance.
Is there a way to get a Tesla Coil to operate at 1/4 wave or do you need to
build a 3 coil system?
I have been battling to get longer than 30cm arcs from my VTTCs. It's
mainly due to my impatience and incompetence but hopefully there is a way
to improve the current system.
I don't have any toroids unfortunately. Will have to get one!
Cheers!
-Wil
On 31/10/2014 7:39 PM, "paul" <tcml88@xxxxxxxxxxx> wrote:
>
> > is the topload acting as a capacitive transmitter?
> > I mean is it transmitting using a dielectric effect
> > rather than electromagnetic.
>
> The electric field dominates, therefore mostly capacitive
> coupling to surroundings. Far field is negligible which
> is why you don't need a transmitting licence.
>
> > does the topload turn the secondary into a parallel or
> > series LC network?
>
> The TC is either parallel and series resonant - depends on
> your viewpoint. Looking between top terminal and ground
> you see a parallel resonance. Looking into the base of
> the coil you find a series resonance. Same when you add
> a topload but with increased C.
>
> > could the secondary topload be sufficiently sized to match
> > the inductance of the secondary?
>
> Not sure what you mean by 'match' here? Coil and topload will
> form a resonator with whatever L and C they happen to have.
> If you want a particular frequency then you must choose the
> topload to have the correct C to achieve your target frequency.
>
> But usually F is not a design target.
>
> The topload protects the top of the coil from high field
> strengths, and matches the output of the coil to its load
> (usually a spark loading). These considerations determine
> the size and shape of topload. That fixes the topload C.
> In combination with the coil, that determines resonant
> frequency. Then you design a primary to match that F.
>
> > ...Tesla used an elevated capacity. Was this for transmission
> > purposes
>
> Probably the intention was to extend the E-field as far as
> possible.
>
> > ... or could it act as a delay line between the inductor
> > and capacitor?
>
> No significant delay.
>
> If the topload is too far above the coil it wont be able to
> protect the top of the coil. Can consider two toploads, one
> toroidal just above the coil and another of any shape which
> can be placed remote from the coil.
>
> Formation of long sparks requires short very rapid bursts of
> charge delivered into the developing streamers. The coil only
> provides charge slowly (compared with the streamer formation
> timescale), so the topload needs to act as a charge reservoir.
> A sphere is the worst possible shape for this - for a given
> size and voltage a sphere is the shape that stores the least
> amount of charge. A sphere is also poor for controlling the
> field around the coil top. Toroids are good in both respects.
>
> I'll just add that there is no formula to calculate the ideal
> topload size/shape to give max spark length for some given
> power level. Coilers have discovered over the years that
> large is good, and larger can be even better. But there must
> be an optimum size - too small and not enough charge stored,
> too large and not enough E-field to push out the streamers.
>
> --
> Paul Nicholson
> --
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla