Re: Ratio of primary outer dia.

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts" <m.j.watts-at-massey.ac.nz> 

On 8 Dec 2003, at 8:10, Tesla list wrote:

 > Original poster: "RIAA/MPAA's Worst Nightmare"
 > <mike.marcum-at-zoomtown-dot-com>
 >
 > So a large primary inductance with smallish cap (x-ray transformer) is
 > worse than a small inductance with large cap (pole pig) assuming same
 > kva and Fres?

No, but that approach forces you to use a high inductance secondary
to maintain a high Ls/Lp ratio (for voltage gain). A high Lp/Cp ratio
is desirable to minimize primary losses but stuffing a high secondary
inductance into a smallish secondary coil increases secondary losses.
Hence, the approach is more suitable for large coils. As always in
engineering, there are tradeoffs and the law of diminishing returns
applies. Things tend to pretty much balance out in TC-land as
evidenced by the fact that one can benchmark a coil against John
Freau's sparklength vs power formula which doesn't even take physical
coil factors into consideration. It *is* a benchmark however and it
is easy to design a coil which falls well short of its ideal.

Malcolm


----- Original Message ----- From: "Tesla list"
 > <tesla-at-pupman-dot-com> To: <tesla-at-pupman-dot-com> Sent: Monday, December 08,
 > 2003 2:10 AM Subject: Re: Ratio of primary outer dia.
 >
 >
 >  > Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com>
 >  >
 >  >
 >  > There is no "exact ratio" because the design depends on two
 >  factors, not > one.  These two factors include the primary inductance
 >  and the primary > capacitance. > > Our procedure goes something like
 >  this: > > First, more capacitance usually provides higher peak
 >  currents and more > energy available to couple into the secondary
 >  system.  Keeping this > important factor in mind, we tune as follows:
 >  > > Using a "scrap wire" primary, usually 24 turns to 30 turns, we
 >  tune the > system with the size capacitor a computer program
 >  dictates.  Now, you have
 > a
 >  > basic tune with fixed capacitance.
 >  >
 >  > If you are in the range of 6-12 turns (with NST) or 3-8 turns (with
 >  pole > xmfr), you have a good, but not optimum capacitance. > > Now,
 >  we tune for optimum capacitance by adding more capacitors and
 > reducing
 >  > the # of primary turns.  Our final goal is 6-12 turns with NST or
 >  3-6
 > turns
 >  > with pole xmfr.  A large capacitance value provides more peak
 >  current and > additional energy available to couple into the
 >  secondary system. > > This "turns reduction" as I call it usually
 >  provides significant
 > improvement
 >  > in secondary output (assuming your spark gap is up to proper
 >  quenching of > additional current). > > If you increase the cap size
 >  you may also have to adjust your power supply > to provide more
 >  energy to charge the larger cap. > > These procedure are time
 >  consuming but assist in the quest for optimum > output for any system
 >  large or small. > > Dr. Resonance > > Resonance Research Corporation
 >  > E11870 Shadylane Rd. > Baraboo   WI   53913 >  > >  > Does someone
 >  have a rule of thumb for determining  primary outer
 > diameter
 >  >  > based on secondary diameter and height?
 >  >  > I did an archives search, but came up with nothing definitive.
 >  I am
 > sure
 >  >  > that there is a ratio for optimum performance.  Also, if John
 >  Couture
 > is
 >  >  > reading this, are you planning on publishing an updated version
 >  of your >  > construction guide?  Mine is from the early 90's, and I
 >  was curious if
 > you
 >  >  > are planning to integrate some of the last decade's developments
 >  into a > new >  > book.  I certainly hope so. >  > >  > Thanks, >  >
 >  John Richardson > >
 >
 >
 >