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

["Tesla list" <tesla-at-pupman-dot-com>]

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

Hi Dave -

Your number of turns hasn't physically changed and is 224 correct? With the
3 windings, I agree you
have 3 x the area. Account for 21 awg size x 3, but I don't see why the
number of turns would be
changed (I'm assuming each wire has 224 turns). I tried this and Acmi says
5.839mH (near your
measurement). There may not be a solution for your 3 wire coil. True that
the physical area is 3 x
the wire size, but Acmi is looking at 1 wire 3 x the size, not 3 smaller
wires side by side. The
wire is basically non-uniform for all practical purposes and this is
probably where the discrepancy
exist. If any program could get close or will in the future, it will be
Acmi. But like all other
programs, it's only as good as it's inputs and it's limitations.

However, there should be no problems at all with the single wire coils like
your 13 inch coil. Who
knows, maybe you can get your hands on a second LCR somewhere to aid
verification. I'm sure
Radioshack would just love to measure the coil (assuming they have an
inductance meter).

Take care,
Bart

Tesla list wrote:

> 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
> }