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Re: optimal aspect ratio
Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Mddeming-at-aol-dot-com>
In a message dated 7/29/02 2:28:30 AM Eastern Daylight Time, tesla-at-pupman-dot-com
> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> Fellow coilers,
> The latest edition of a German radio amateur magazine is dealing with
> the optimal aspect ratio of cylindrical single layer air core coils
> (like the solenoid type primaries in our TC systems).
> The author proofs, that coils with an aspect ratio length/diameter of
> 0.45 provide maximal inductance and minimal resistance.
> The number of turns is calculated from
> 7.43 x 3rd root(L in ÁH/dia in mm)
> Unfortunately there is no URL available (the publisher wants to sell
> the copies of course).
Hi Herwig, All,
The detailed derivation of Lmax also appeared twelve years ago in
"Modern Tesla Coil Design Theory" by Duane A. Bylund, Tesla Book Co. Chula
Vista, CA, 1990, ISBN # 0-914119-09-5. There is also a similar derivation of an
Lmax for flat coils of B=8R/11 where B is the width of the coil, defined as
ro-ri, and R is the average diameter, defined as (ri+ro)/2. In the case of a TC
with vertical coil, this optimal point may not be a practical one, since at the
ratio where L is maximum (dL/ds=0) the voltage drop between turns, (dV/dh) is
extremely high, requiring higher insulation values, etc. Very low aspect ratio
coils would also be limited in spark length due to the proximity of top load
I did an as-yet-unpublished article for the Geek Group on this subject
about 6 months ago and would be happy to send copies or send it to Terry to
post, if there is any interest.