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RE: Barts Flat Coil Dimensions Was: Dimensions of my flat spiral coil



Original poster: "David Thomson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>

Hi Bart,

Thanks for the sample.  I was able to look at your sample input file and
determine what was wrong with mine.

When calculating the inductance for my trifilar coil, the one I'm using at
the moment, I had to assume a few things.  First, since the three wires are
essentially one wire, I had to take the number of turns to be one third of
the total.  So instead of 224 turns I used 74.66 turns.  And instead of
using 21 awg for the conductor, I used three times the diameter which is
.085383 inches.  This gave 648uH.  My measured inductance is roughly 6.23mH.
Maybe the flat conductor is throwing off the calculation?

units inches

secondary {

   radius1 .125     ; Starting radius
   radius2 6.375     ; Finishing radius

   height 0

   conductor .085383
   turns 74.66
}

primary {

   radius1 14.5
   radius2 18

   height .25

   conductor .375
   turns 3.5
}

    SCNY.L| SCNY.R|    PRMY.L| PRMY.R
  648.7 uH|   0.05|   19.7 uH|   0.00
SCNY-PRMY.M|SCNY-PRMY.K
     9.2 uH|     0.0816

As for the single wound flat spiral secondary coil, the acmi program
calculated the inductance to be 5.871mH whereas my spreadsheet calculated
the inductance at 5.697mH.  Yet my LCR meter reads 35.0mH.

To check the accuracy of my LCR meter, I calculated the inductance of a
single wound solenoid coil with 4.5" diameter, 9.625" winding length, and 21
gage wire.  The calculated inductance was 4.7mH.  I measured the inductance
with my LCR meter at 4.6mH.

So my LCR meter seems to be fine, at least when working with solenoid coils.
I don't know yet how we are going to resolve our discrepancies.

Dave

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Monday, February 18, 2002 8:29 AM
To: tesla-at-pupman-dot-com
Subject: Re: Barts Flat Coil Dimensions Was: Dimensions of my flat
spiral coil


Original poster: "Barton B. Anderson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi Dave,

Some help below..

Tesla list wrote:
>
> Original poster: "David Thomson by way of Terry Fritz
<twftesla-at-qwest-dot-net>"
> <dave-at-volantis-dot-org>
>
> Hi Bart,
>
> I'm having a tough time getting the parameters right.  I keep getting an
> unrecognized option error.  As soon as I figure out what I'm doing wrong,
I
> tell you if it gives a better inductance calculation than the standard
flat
> spiral coil formula.
>
> Dave

You'll find standard L equations are close to Acmi, because they are close
to
the inductance of the coil. Using a stardard spiral equation, I calc'd
11.4mH
and measured 12mH. ACMI however calc'd 12mH. (these values on my 2nd spiral
coil).

Below is an input file I used today for Acmi. You could probably just copy
it
into Notepad and save it as "flat.in". (the extention isn't important - just
that it's called out properly when piped into Acmi).

Also, open Notepad and copy the following into it, then save it as
"Acmi.bat".

acmi<flat.in

All you have do then is run Acmi.bat and the input file (flat.in) is piped
into
Acmi.

A note about my file. The primary I'm using is a flat configuration which
will
be below the secondary about 6 inches to start out due to coupling reasons.
Anyway, you can simply ignore the primary and change the secondary
parameters
for your coil.

Hope this helps,
Bart

Here's the "flat.in" file.

; Flat Spiral Secondary.
; Turns are rounded to nearest integer.

units inches

secondary {

   radius1 0.3125      ; Inner turn radius
   radius2 6.98875     ; Outer turn radius

   height1 0.0   ; leave at 0 for flat coil
   height2 0.0   ; leave at 0 for flat coil

   conductor 0.01005   ; bare wire radius
   turns 298  ; number of turns
}

primary {

   radius1 4.5         ; inner radius
   radius2 6.122       ; outer radius

   height1 -6.0     ; inner turn height
   height2 -6.0     ; outer turn height

   conductor 0.125      ; bare wire radius
   turns 3.7  ; number of turns
}