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Re: Off-axis primary inductance
Tesla List wrote:
>
> Original Poster: Gary Lau 22-Nov-1998 1518 <lau-at-hdecad.ENET.dec-dot-com>
>
> >"I had heard the well circulated wive's tale that off axis L would waste
> >energy. This test graphically proved that it does not.
> >
> >The practical conclusion is that it IS technically acceptable to place a
> >high quality air core tuning coil in series with the Tesla coil primary
> >coil in order to achieve 'fine tuning' without throwing away hard won RF
> >tank circuit energy!
> >
> >Real valuable knowledge gleaned by the actual doing.
> >
> >Robert W. Stephens
>
> This sounds reasonable. Now it makes me wonder about the importance of
> low ESL tank capacitors. If it's okay to have inductance scattered
> anywhere throughout the tank circuit as long as one's coupling is not
> compromised and pri/sec resonance is maintained, why should ESL matter?
> Could it be that only dielectric, and DC plus skin-effect resistive losses
> matter in the tank? Or is capacitor ESL correlated to resistive losses
> in the cap as well?
>
> Gary Lau
> Waltham, MA USA
Gary,
Fortunately, capacitor ESL shouldn't matter very much with
reasonably-constructed caps. Even an end-terminated rolled cap has much
of it's inductance cancelled because of opposite current flows through
its plates. The main reason to keep ESL low is that the tank capacitor's
ESL is "in parallel" with its own capacitance, and can form a separate
parallel resonant circuit. This parasitic LC circuit can "strand" a
portion of the primary circuit's energy that would otherwise go into
making sparks. Keeping the cap's ESL low elevates its self-resonant
frequency, hopefully to the point this effect is negligible at the
operating frequency of your system. The moral of the story: Keep
capacitor ESL low... just don't get fanatical about it! :^)
-- Bert --