Re: Mutual Inductance & K Factor

["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 John,


Tesla list wrote:

> Original poster: "John H. Couture by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
>
> Bart -
>
> Thank you for the comparison data for Kurt's coil. I am thinking of changing
> the JHCTES Ver 3.3 program to bring it up to date. It obviously needs to be
> changed to conform more closely with the Mandk, Acmi, and Java9.1 programs.

With Acmi ID, OD, Turns, and conductor are inputs (and thus identified this
way in Kurts file).
Typically, I plug in ID, conductor, and turns to get OD. Java9.1 works real
nice for providing this
info into the other programs like Acmi. For me, they work hand in hand. The
ID and OD are the only two
measurements really required because everything else can be found. In Kurts
case, I simply changed the
e-e spacing until OD matched Kurts measurements, then verified against all
the turns he measured OD
on.


> Someday coilers will make K Factor tests using the frequency method and with
> the mutual inductance test we should have more accurate K Factor values.

Agree.

>  Your comment to pay attention to OD for each turn of Kurt's coil has made me
> look into the JHCTES and Java programs in more detail. To compare these two
> programs with the Kurt data it is necessary to reverse engineer the data to
> conform with the input requirements of the programs. This can be a problem
> in finding the inputs. For example I noted your primary wire diameter plus
> the wire spacing gives the center to center (c/c) distance or the edge to
> edge distance = .7867. However, which Width of turns should be used, 3.1203
> or 2.725 for the 3.9663 Pri turns?

2.725 would be correct and you should have come to the same number in the
math below for both methods
of equating this value.

>     c/c = .3937 + .393 = .7867 inches
>     Width of turns = .7867 x 3.9663 = 3.1203 ?

The above is an e-e calculation. Simply remove 1 turn to change to c-c.
Width of turns(c-c) = (.7867 x 3.9663)-.3937 = 2.725

>     c/c dist. = (OD-ID)/(2 x turns)
>               = (25.14 - 19.69)/(2 x 3.9663) = .6870
>     Width of turns = .6870 x 3.9663 = 2.725 ?

Interesting way to get there. The end result is correct.

> For the JHCTES avg radius
>
>  Avg radius = (OD-ID)/4 + ID/2
>             = (25.14 - 19.69)/4 + (19.69)/2
>             = 11.21
> If the Width of turns is 2.725 the program c/c = .69 inches
> This works OK with the 3.97 Pri turns and the 1.97 Pri to Sec clearance of
> your data.

Yes. The spacing input was changed to e-e after enough requests. Using c-c
on this particular input
always caused input errors with coilers. I guess it's easier to design with
what one can visualize.
I'm ok with that because if used for design prior to building, it's ideal.
Once the coil is built and
the coiler wants to use the program to look at various output, then this
input should be adjusted to
match the measured OD value, which then considers all the little variations
that stack up when the
primary is actually built.

> With one Pri turn the JHCTES gives Lm = 33.98 and K = .125 which compares
> favorably with the .1244 of the Mandk and Acmi programs.   However, when the
> Sec is raised to 3.4" above the Pri the K Factor is .097 compared to the .68
> of the Mandk and Acmi. The coupling reduces very fast with the Mandk and
> ACmi programs. I would be interested in seeing this verified with the
> frequency test.

It's possible Kurt may have tried the frequency method out on this coil at
one time or other. His
measurements on this coil were some time ago.

Take care,
Bart