Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>
Hi All,
Javatc has been updated to version 10.i which now includes a
secondary Q and Rac output. Also, the recommended wire size has been
removed for now.
Recently, Gerry wrote a program for Q based on the Fraga equation.
I've been mulling through approximately 140 Q measurements, most of
which are thanks to Malcolm (Medhurst would have been very proud!).
During my episode with the data, I've found that Fraga's Rac can by
used with both closewound and spacewound coils. If we were to use
Fraga's calculation as it is, our "real world measurements" would
see very high error which is useless to coilers.
I have included a factor to Fraga's Rac to account for h/d and the
spacing ratio of coils. It's very simple.
Fraga's Rac x [1+(spacing ratio/hd ratio)]. Q of course is
calculated as Q = sqrt(Les/Ces)/Rac.
Where:
h/d = coil length / coil diameter
spacing ratio = turns/(wire diameter/coil length)
Here is a graph of Javatc vs. measurement of 128 loaded coils. The
loaded coils include toroids, spheres, and discs.
http://www.classictesla.com/temp/Rac_Q_Chart.gif
For h/d ratios > 2, the prediction is good. Ignore any coil less
than an h/d of 2. The numbers are somewhat good for loaded coils,
but for bare coils, they are useless.
To put this in some perspective:
h/d ratio's of 5:1 showed that 80% of the measured coils were less
than 10% error
h/d ratio's of 4:1 showed that 75% of the measured coils were less
than 10% error
h/d ratio's of 3:1 showed that 50% of the measured coils were less
than 10% error
Q is one of the most difficult to predict based on an initial
design. Most don't even attempt it. Q is also one of the harder
measurements which requires correct equipment, procedure, and
experience. Since many do not have the equipment or experience,
Javatc will help by providing a good ballpark figure to consider
during a design process.
Many thanks to Malcolm for his excellent measurements on a "VAST"
number of measurements with top of the line equipment. Measurement
data like this is as good as it gets. Anyone who has ever measured Q
(or even provided measurement data) can appreciate the hard work and
effort Malcolm put into his measurements.
And of course, Javatc is where it always has been:
http://www.classictesla.com/java/javatc.html
Take care,
Bart