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[TCML] Re: Source for 1H air-core inductors



Hi Harvey,


From: Greg Leyh <lod@xxxxxxxxxxx>
Date: Thursday, June 18, 2009, 8:40 PM
Hi All,

I can offer one potential source for 1H air-core inductors;
two will come free with purchase, as part of the NLL
Project.  ;)

Each of the NLL secondary windings will have an inductance
just over 1H.
If desired, they can be arranged in series for 2H,
total.  The 1H claim can be confirmed using Faraday's
Law; secondary coilform dimensions are 29ft dia, 105ft
winding length, and 1.8" turn-turn
spacing.   GL

>

Jesus of Mary, I must protest. Two distinct observations can be made concerning high inductances. First is the ratio of resistance to inductive reactance at the tested frequency whereby the "acting" q factor of the inductor can be determined upon further balancing of equal capacitive reactance; both in series and in parallel to ascertain the "real" actions of the circuit compared to the "theoretical" Q factor that should exist.
In this regard simple measurements exist to show that high inductances may be gained by the transformer iron core as a toroid primary/secondary action. However the gain of inductance  there is not practical for resonance schemes. I doubt whether a single 1 henry coil would do much good either. It is simply impossible to believe that given the supplied dimensions of this coil that it would only be in the micro-henry range still. Indeed I am building a one inch separation wind of ten ft diameter near 47 windings, so my observations on that completed structure can be shown. It takes 9000 windings of 23 gauge wire on a 12 lb spool to make a 2.4 H air core inductance. I dont know how you can use Faradays law to deduce the above, or whether it is just a joke upon people who seriously look upon these things.
HDN


Not exactly sure what you're protesting here or what you think the joke might be. From Faraday's Law, the familiar 'coil-makers equation' can be derived: L = (4pi*10^-9 * N^2 * A) / l

Note that the units for x-sectional area [A] and length [l] are in cm.

Plugging in the values listed above, the equation yields about 1.15H.
Assuming a skin depth of 38mil on 4/0 cable, the total AC resistance of the winding is about 14ohm. This yields a calculated Q of about 2000 at 5kHz although the actual unloaded Q is likely to be significantly lower.

-GL
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