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Re: E-Tesla = Medhurst

Hi Terry,

I thought i would try to get a few points from your programe for the ends of
Medhursts's table.  But the programe you gave the link to does not work on
my PC.  After inputting the data it asks if the data is correct if I reply
yes or no it contiuously ouputs an error message???

In the file I sent you  will note, if you have not already done so,
that there is a minimum in med C.
I was trying to check if E-tesla reproduced that minimum.  I don't
understand why If med C is just referred intrinsic C linear wieghted.  Why
would the intrinsic C go down then up as you increase the hieght? I find it
hard to accept that when you increase one dimension of something its C goes
down?? If this is true then reffering process is more complicated than I
have deduced.

regards bob

-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Cc: alwynj48-at-earthlink-dot-net <alwynj48-at-earthlink-dot-net>; malcolm.watts-at-wnp.ac.nz
Date: Monday, June 12, 2000 2:10 AM
Subject: Re: E-Tesla = Medhurst

>Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>Hi Bob,
>At 01:40 PM 6/11/00 -0400, you wrote:
>>Hi Terry.
>>After a little more thought or was it a lot more thought.
>>For a large parallel C the voltage a long the coil  approaches a linear
>>function regardless of what the distribution is with out parallel C.  ie
>>current flowing in the distibuted intrinsic C hardly effects the voltage
>>across the coil because the coil current is much higher than the intrinsic
>>Hence the additional current flowing in to the distributed intrinsic C is
>>only a function of the voltage and C.  This is even true for low H/D
>>with almost unity coupling (auto transformer action).
>>Under such condition the distibuted intrinsic C can be refereed to one end
>>by simple summing the  currents.  Because the currents are proportional to
>>the voltage a voltage weighted intrinsic C is equal to a single C you must
>>put in parallel with the coil to have the same total current flow that the
>>distibuted intrinsic C had.
>>Hence if you run E-Tesla with a linear voltage and on an isolated coil it
>>will produce med C. This is a theoretically valid comparison and should
>>correlate to approximately. 1% in C not F. A good test of the theory and
>Ok.  I stripped out E-Tesla5.50 to put a linear voltage on the secondary
>and stick it in free space and all that.  The program is at:
> http://users.better-dot-org/tfritz/site/programs/ETMED.ZIP
>I then ran the program with a 200 grid on 10 inch diameter coil of various
>lengths.  I then compared the results to Medhurst.
>H/D Cmed C ET5 calc Error %
>10.0 1.32 1.2056 -8.66
>9.0 1.22 1.1238 -7.89
>8.0 1.12 1.0482 -6.41
>7.0 1.01 0.96745 -4.21
>6.0 0.92 0.88716 -3.57
>5.0 0.81 0.80313 -0.85
>4.5 0.77 0.75848 -1.50
>4.0 0.72 0.71428 -0.79
>3.5 0.67 0.66897 -0.15
>3.0 0.61 0.62244 2.04
>2.5 0.56 0.57424 2.54
>2.0 0.5 0.52573 5.15
>1.5 0.47 0.4758 1.23
>1.0 0.46 0.42783 -6.99
>The graph is at:
> http://users.better-dot-org/tfritz/MedComp.gif
>Note that both graphs have a bend at 5.0!?!  Must be something magical
>happening at that point.  Below 5.0 Medhurst tracks very well until the
>coils get really small.  I wonder if the error is him or us? :-)  ET5 looks
>like two straight lines while the Medhurst graph is showing obvious signs
>of a little experimental error.  The program did about 300 billion more
>calculations than Medhurst did so it should be straight! :-))  I wonder if
>I dare say that the computed numbers "may" be more accurate than Medhurst's
>in the 2.5 to 5.0 range?
>Looks like Bob is again right!!
>>If you run it with a ground plain it will produce med C with a ground
>>But as Medhurst did not produce such a table you can not make any valid
>>comparison.  The true C / TM equation is again theoretically valid for an
>>isolated coil.
>>When I say valid for..... I dont mean its not valid for other conditions
>>means only that I can only prove its valid for that condition/s.
>>So E-Tesla can be said to be theoretically accurate for coils with
>>approximately 1000 turns (low turn to turn C effects), for large top loads
>>and with a ground plain sufficiently below the coil (at least several
>>diameters)  that the inductance is valid.
>>Note E-Tesla must include some  internal C (turn to turn C)  effects
>>the C is determined with a voltage profile as opposed to a unity profile
>>(the correct way to calculate intrinsic C) then weighting the result with
>>the voltage profile.   However as the  internal C has mostly internal
>>current I don't know if it can be refereed to the one end and I don't if
>>you treat the internal coupled flux is valid or  correctly produces  a
>>reffered C to one end.  That will require more thought but as I believe
>>a small effect I am not motivated to try. If you try it both ways and the
>>answer (refereed C or med C) is significantly different then I will be
>>motivated to try.
>>Now what about the self resonant case.  When the only current flowing in
>>coil is due to the distributed intrinsic C both the voltage and current
>>not linear so the above method of referring the intrinsic C to one end is
>>not valid.  A 5% to 10% error in F is  10% to 20% error in C or L.
>I am working on such things to further increase accuracy...
> Terry
>>Regards Bob
>>You can put this on the list if you think anybody else is interested