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Re: Inductance calculations
Original poster: "Barton B. Anderson by way of Terry Fritz <teslalist-at-qwest-dot-net>" <classictesla-at-netzero-dot-com>
Antonio,
Tonight I tore down and stretched out the coil. Yes, it is tubing (I needed
the coil to hold shape). When you mentioned the smaller wire size, I
decided to stretch it out to at least the maximum of my meter leads. The
results are impressive! Once again, nature tells the tale.
Dimensions: r1,r2=.485775, h=2.1336 at turn 5, wd=.009525): (L=uH,
units=meters).
height turns meas. fantc Wheeler Lundin | inca.h Snow
------ ----- ----- ----- ------- ------ ------ -----
2.1336 5 17 9.02 9.06 9.08 | 18.15 18.73
1.7051 4 13 6.92 6.97 6.97 | 14.26 14.65
1.27635 3 10 4.86 4.89 4.89 | 10.41 10.63
0.84785 2 6 2.87 2.90 2.89 | 6.63 6.70
0.4191 1 3 1.08 1.09 1.09 | 3.02 3.00
Note:
With the XT's 1uH minimum, I measured 2uH of lead inductance (already
accounted for in numbers above). The leads inductance did toggle between 1
and 2uH, but settled on 2uH. Thus, I feel that inca and Snow are likely
calculating the inductance better than I can measure.
I think you have a winner with Inca! This coil was spaced out far enough
that the conductor size appears small relative to the distance. And with
that thought, if we were capable of decreasing the conductor size
extremely, we should be able to achieve the same inductances with less spacing.
Obviously, these geometry's are impractical to coiling, but excellent for
the test. I think I've learned a little something today. Very cool!
Take care,
Bart
.
Tesla list wrote:
>Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz
><teslalist-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>
>
>Tesla list wrote:
> >
> > Original poster: "Barton B. Anderson by way of Terry Fritz
> <teslalist-at-qwest-dot-net>" <classictesla-at-netzero-dot-com>
>
>Bart,
>
> > Tonight I wound a 5 turn helical at nearly 1 meter diameter. I read
> > inductance with the 27XT.
>
>I was avoiding this... Thank you for the experiment.
>
> > For the measurement values, I already removed lead length inductance
> > (dimensions in meters, L in uH). The 27XT cannot show enough digits beyond
> > 1mH, but ok to see how programs parallel.
> >
> > Final dimensions: r1,r2= .485775, b=0, wd=.009525
>
>A tube?
>
> > height turns meas. fantc inca.g moshier
> > ------- ----- ----- ----- ------ -------
> > .092075 5 49 49.33 49.3 49.15
> > .082042 4.5 42 41.37 ----- 41.2
> > .071882 4 33 33.97 33.79 33.79
> > .061722 3.5 27 27.14 ----- 26.96
> > .051562 3 20 20.92 20.83 20.73
> > .041402 2.5 15 15.36 ----- 15.17
> > .031242 2 9 10.5 10.38 10.31
> > .021082 1.5 6 6.4 ----- 6.23
> > .010922 1 2 3.32 3.02 2.99
> >
> > As you can see, they all agree with measurement and follow as expected.
>
>(The numbers that I get with Fantc are a bit different. 49.39 in the
>first case and 3.23 in the last.)
>Really, in this condition the calculations agree well, and Nature
>agrees with them all, what is very good. Note, however that
>the coil where I noticed the difference was made with thinner wire, with
>2 mm of thickness. Thin wire causes the Maxwell and Snow (Moshier)
>formulas to give larger values. Ok that big coils with thin wire are
>rare in Tesla coiling... With 2 mm wire, the difference appears again
>when the number of turns is greater than 1:
>
>height turns fantc inca (e.f.) moshier
>------- ----- ----- ----- -------
>.092075 5 49.41 53.97 53.93
>.051562 3 20.96 23.63 23.59
>.010922 1 3.24 3.98 3.95
>
>I have now implemented in the Inca program the same formula that Moshier
>uses (Snow), for comparison. It doesn't agree exactly with Maxwell,
>but gets always very close (0.1% of difference when the spiral
>is considered), and is fast.
>
> > don't think the problem realized is with small number of turns (although
> > the small turns will aggravate the problem). The problem I see occurs when
> > the loop itself falls away from the horizontal and tends towards the
> > vertical, as if it is stretched out. The further it is stretched, the more
> > it resembles a straight conductor. Fantc, Acmi, and MandK move toward
> > Wheeler as the coil is stretched which are is the geometry we've been
> > discussing. Because of this coils large radius and distant proximity, the
> > single turn should be very near to the straight wire inductance. When I
> > tear down this 5 turn primary, I'll stretch it out to where the height =
> > diameter and measure.
>
>This will show a difference. Do you have some #18 wire around? with 1 mm
>of wire diameter an even larger difference shall be noticeable.
>
>Antonio Carlos M. de Queiroz
>
>
>
>