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Re: Lower secondary cself => better performance?
Original poster: "Area31 Research Facility by way of Terry Fritz <twftesla-at-uswest-dot-net>" <rwstephens-at-hurontario-dot-net>
Very nicely worded explanation. I agree with your theory entirely.
Robert W. Stephens
AREA31 Research Facility
AREA31 Radio Observatory
Hangar31 Vintage TV Museum
> ----- Original Message -----
> From: <mailto:tesla-at-pupman-dot-com>Tesla list
> To: <mailto:tesla-at-pupman-dot-com>tesla-at-pupman-dot-com
> Sent: Tuesday, February 13, 2001 13:25
> Subject: RE: Lower secondary cself => better performance?
> Original poster: "Lau, Gary by way of Terry Fritz
> Hi Paul:
> Concerning why large toploads appear to give superior performance, as
> opposed to using a small one designed to maximize topload voltage - what
> follows is the reasoning I have heard and understood. You no doubt have
> studied these issues in far greater depth than I have, so I would enjoy
> hearing your take on this.
> The total secondary capacitance Csec occurs in two components - the Ctop
> from the toroid, and Cself, the distributed capacitance of the secondary
> windings. When a streamer breaks out, the charge from Ctop is there with
> just the metal in the toroid between the Ctop charge reservoir and the
> streamer where it wants to go. But the charge in Csec is distributed along
> the length of the secondary. There are many mH of inductance between most
> of this charge and the streamer that wants to drain it. The streamer is a
> very high frequency, short-lived event, so the intervening inductance just
> won't allow it to be useful in terms of feeding the streamer. So it is
> desirable to have as large a portion of Csec in the form of Ctop and as
> little as possible in the form of Cself. I think this is why space wound
> secondaries are sometimes favored, as it minimizes Cself (in addition to
> lowering Rac and raising the Q) of the secondary, though I've heard of no
> direct experimental performance comparisons. Adding a larger topload to an
> existing secondary serves to raise the ratio of Ctop/Cself.
> When streamers occur may be one (important!) instance where the lumped model
> of the secondary may not accurately describe what happens should charge be
> drained from Ctop to a streamer, but "stranded" in Cself.
> I'm not sure that maximizing the theoretical peak pre-breakout secondary
> voltage is useful in maximizing streamer length. Maximizing the efficiency
> of getting the total energy stored in the secondary to the streamer is.
> Easier said than done, for sure.
> Comments MOST welcome!
> Gary Lau
> Waltham, MA USA