From: boris petkovic
Date: Sat, 16 Dec 2000 03:47:12 -0800 (PST)
Subject: Re: [TSSP] Coils at high elevation
--- Paul wrote:
> I wrote:
>
> >> Using the new program the f1 error for H/D=1 in
> >> Malcolm's catagory (a)
> >> coil 1 measurements is +7.7%, and for Mark's 875
> >> turn coil, +16.3%.
> >>
> >> These errors can no longer be attributed to
> >> defects in the capacitance
> >> determination software and must be due either to
> >> an inadequate
> >> representation of the environment, or more
> >> worryingly, a problem with
> >> the application of internal capacitance within
> the
> >> model.
>
> boris petkovic wrote:
>
> > You mean interturn capacitance effect of a winding
> has
> > such a dramatic influence at Fo?
> > If so ,I don't agree .At least,It couldn't be
> reason
> > for 875 turn coil.
> > 16% error for 1/4 wave resonant freq.is way too
> much
> > to be caused by neglecting interturn capacities
> here.
>
> I guess you're thinking of the direct interturn
> capacitance
> between neighbouring turns - what I call the
> 'Palermo'
> capacitance [*].
----
Yes.Thanks for the name.Now I know how to call it.
----
I agree this by itself is far too
> small to
> have significant effect - even its value is in doubt
> due to
> the proximity effect. My definition of internal
> capacitance
> includes that between remote turns, a much smaller
> capacitance
> but there are more of them and they are charged to a
> higher
> voltage. Their combined effect accounts for around
> 5-10% of the
> overall capacitance at normal coil elevations.
---
Despite that 5-10% energy storage part,overall Cint
influences to 1/4 fo of usual way built close wound
coils (cylindrical shape of winding not a conical)
less than might be orginally supposed by upper percent
presented.
As fn resonant frequency increases situations change
-the effect of Cint influence to higher harmonic
frequency cannot be neglected anymore.
This year I sent Malcolm an outline of my papers
where I explained how and why that appears.
-----
At
> high elevations,
> external capacitance is reduced and the internal is
> much more
> significant. For Malcolm's h/d=1 coil, the internal
> capacitance
> accounts for over 50% of the total E-field energy
> storage [+].
----
Very much indeed.
But it is my opinion anyway that factor of influence
to 1/4 wave freq. is smaller than
g=sqrt(Cexternal)/sqrt(Cinternal+Cexternal)
where fo=g*foe
foe means calculted res. freq. taking into account
just external capacity of coil.
-----
> Therefore if either the determination of, or the
> implementation of,
----
I think it could be implemetation but I'm not sure.
----
> internal capacitance is faulty in any way, the
> effect will be up
> to 10 times worse at high elevations. The effect of
> internal
> capacitance on the amplitude profiles is
> particularly interesting,
> so I'm keen to use high elevation measurements as a
> means of
> validating the internal capacitance modeling.
-----
Fine.Msm will decide
>
> [*] A.J. Palermo, 'Distributed Capacity of
> Single-layer Coils',
> Proc IRE 1934, Vol 22, p897. Contributes around 1%
> or less to
> coil capacitance, depending on how much proximity
> effect you
> allow for.
>
> [+] Mark's coil, which exhibits a higher discrepancy
> in f1, has
> a Cint contribution of only 17%, since it has h/d=6
> which gives a
> smaller Cint to begin with. This leads me to believe
> that Cint is
> not to blame.
----
Becouse of high h/d ratio that is my thinking too.
Regards,
Boris
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