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RE: More Coupling...



Original poster: "John H. Couture by way of Terry Fritz <twftesla-at-uswest-dot-net>" <couturejh-at-worldnet.att-dot-net>


All -

I have entered Bart's coil parameters into the JHCTES/2.3 program with the
following result.

            acmi           Bart             JHCTES/2.3

Pri         108.6 uh       107.13 uh         108.8  uh
Sec 1000 T   80.3 mh        87.6 mh           80.21 mh

Mut Ind     439.8 uh       627.0 uh          482.63 uh
K Factor    .15            .20               .16

Pri turns     ?            11.6              11.56

As with other past Tesla Listings trying to get test data to agree with TC
programs is always a struggle. It is obvious that a thorough understanding
of both TC testing and programs is required. This is particularly true of
mutual inductance because so few coilers make this test. I have used the
Mutual Inductance and K Factor tests shown in my books and they agree very
well with the JHCTES program. However, these tests were for small coils and
limited in number so I am always interested in the test results of other
coilers.

Note that the JHCTES program is an "instant calc" program and not an
iterative type so there could be some differences in results between them.
Also the mutual inductance of the JHCTES is coordinated with the other TC
parameters in the program. This means that many "what if" combinations can
be tried in a short time.

It is unfortunate for TC programs that less than one percent of the TL posts
are in regards to actual TC tests. Of course there are plenty of random
spark length tests but these have little value for TC engineering design.

John Couture

------------------------------

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Sunday, December 17, 2000 5:53 AM
To: tesla-at-pupman-dot-com
Subject: Re: More Coupling...


Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<paul-at-abelian.demon.co.uk>

Barton B. Anderson <tesla123-at-pacbell-dot-net> wrote:

> ... a second look at your graph and the coupling direction was
> clear.

OK, I just made a similar mistake too - I asked for your winding
inductances when in fact you already mentioned them in an earlier
post. Doh!

Comparing acmi output numbers with your measurements, we have

|              acmi            Bart
|            predicts        measures
|
| Primary    108.6 uH        107.13 uH
| Secondary   80.3 mH         87.6  mH
|
| Mutual     439.8 uH        627.0  uH

I'm pleased with the primary agreement because that's the one acmi
will struggle with, if anything.

Your reported secondary inductance is way too high. I took the
dimensions of your secondary from your web page

 http://www.classictesla-dot-com/photos/gizmos/bart.html

as 12.75" diam, 45.0" length, and 1000 turns. The Nagaoka inductance
for this winding comes out at 80.532 mH, which agrees very well with
acmi. (As usual, acmi does a good job with the secondary because a lot
of small turns are well approximated by current filaments).

Could it be that you have a few more than 1000t as indeed your web
page hints? If I adjust the turns to match your quoted secondary
inductance I find 1043 turns are required. With this change, I get

|              acmi            Bart
|            predicts        measures
|
| Primary    108.6 uH        107.13 uH
| Secondary   87.4 mH         87.6  mH
|
| Mutual     458.6 uH        627.0  uH

which puts the self inductance right, but the mutual is still out
by some 30%. That counts as a large discrepancy and more than I would
have expected.

A couple of questions: You measured 2.59V across the secondary when
the primary was carrying 10.95A at 60Hz. Did you measure the
secondary V when the primary current was turned off, as the secondary
will pick up a certain amount of induced voltage just from the back-
ground field of surrounding mains wiring? Was the hair dryer anywhere
near the secondary - near enough for its AC magnetic field to couple
directly to the secondary? I take it your 2.59V was RMS and not peak?

Ed Phillips <evp-at-pacbell-dot-net> wrote:

> Will have to try a similar measurement here
> using a small flat primary I happen to have.

Any coupling measurements you can make would be very welcome - for
any shape of primary.

Regards,
--
Paul Nicholson,
Manchester, UK.
--