Re: Self Capacitance formulas
Subject: Re: Self Capacitance formulas
From: lbliao-at-alumni.caltech.edu (lbliao)
Date: Sat, 13 Jan 1996 09:41:39 -0800 (PST)
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Thanks Ed, for the post. Could you kindly send me the list of references.
If you can point out a little which article has what, that would prevent
hunting those articles that may not be what I want. i am looking for
derivations and also nifty ideas/tricks.
> >From EDHARRIS-at-MPS.OHIO-STATE.EDU Thu Jan 11 20:28 MST 1996
> From: EDHARRIS-at-MPS.OHIO-STATE.EDU
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> Date: Thu, 11 Jan 1996 19:45:39 -0500 (EST)
> Subject: Re: Self Capacitance formulas
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> Hi Ed,
> Mark R. posted the self capacitance formula due to Medhurst
> in a previous post. If you use this formula in conjuction with standard
> inductance formulas for soleniods (like Wheeler's), you can compute
> the self resonant (no top terminal) frequency of most coils. I have found
> that it works very well for predicting most of Malcolm's measured
> If you want to read a little more of Medhurst try:
> "HF Resistance and Self-Capacitance of Single-LAyer Solenoids" by
> R.G. Medhurst, Wireless Engineer, Vol 2, p35, Feb 1947
> *Note: the range of frequencies he used does not allow his Q formulas
> to work at normal Tesla coil frequencies.
> If you are just interested in computing self-resonant frequencies
> there is another method which I have found useful and generally accurate
> to about 10% for all coil sizes - space wound or not. Its limitation is that
> it probably shouldn't be used for aspect ratios (Height/Diameter)<1.
> The formula is:
> 29.85 x (H/D)
> F = -------------------
> N x D
> (hope the ascii came out)
> F= self resonant frequency in Mhz of an isolated coil
> H= coil height in meters
> D= coil diameter in meters
> N= total number of turns
> Make sure the top line reads " (H/D) to the 1/5 power"
> Note that the frequency is a very weak function of the
> aspect ratio (H/D), but a fairly strong function of the number of turns
> and the diameter.
> This is an adapation of the formula for Helical Antennas found
> in Reference Data for Radio Engineers. A form of this equation also
> appears in both of the Corum brother's books:
> "Vacuum Tube Tesla Coils" and "TC Tutor"
> Incidentally, they incorrectly attribute the analysis of the helix to
> Kandoian and Sichak. These guys actually just made a simplification of the
> formula derived earlier by JR Pierce (1947) and Franz Ollendorf (1925).
> I have a list which has more complete references.
> -Ed Harris