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Secondary Frequency(fwd)
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From: Barton B. Anderson [SMTP:mopar-at-uswest-dot-net]
Sent: Wednesday, August 19, 1998 2:35 AM
To: Tesla List
Subject: Re: Secondary Frequency(fwd)
Reinhard,
I would say "He" (whoever He is) is right. Geometry is significant in the
formula (1/ 2pi LC).
L is affected by the radius of the coil (geometry) as the radius is used to
calculate the inductance where L=(R^2 x N^2) / 9R + 10H, here R=radius,
N=number of turns, H=height. This is known as the Wheeler formula.
C is affected by the H/D relationship (geometry). This is the Medhurst
formula where C=K x D.
C = solenoid self-capacitance in picofarads.
K = a constant which depends on the ratio of the coil height and diameter.
D = diameter of solenoid in centimeters.
For coil A, I calculated L = 23.9mH and C = 7.9pF and came up with 367kHz
(unloaded).
For coil B, I calculated L = 40.6mH and C = 7.4pF and came up with 290kHz
(unloaded).
Based on my assumtions, I came up with values different than "He" did, but
our relationship is the same. If you think about how proximity affects both
inductance and capacitance, you can get an idea of why geometric dimentions
are necessary and why these two formula's are used.
Hope this helps,
Bart
Tesla List wrote:
> ----------
> From: RWB355-at-aol-dot-com [SMTP:RWB355-at-aol-dot-com]
> Sent: Tuesday, August 18, 1998 12:31 AM
> To: fwd
> Subject: Secondary Frequency(fwd)
>
> Hi to All,
>
> Below are two given coils.
> What is the frequency of each coil? Another coiler and I disagree on the
> resonant frequency of these two coils. Can somebody help?
>
> Coil A:
> 21.7" long
> 3" diameter
> Wound with 1230 feet AWG 28
> He says 418kHz (I say 200 kHz)
>
> Coil B
> 10.84" long
> 6" diameter
> Also wound with 1230 feet AWG 28
> He says 275kHz (I say 200 kHz)
>
> Who is right??
>
> Thanks,
> Reinhard