RE: Mutual inductance and K factor

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

Original poster: "J. B. Weazle McCreath by way of Terry Fritz <twftesla-at-qwest-dot-net>" <weazle-at-hurontel.on.ca>


At 10:14 PM 24/10/01 -0600, you wrote:
>
>Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<couturejh-at-telocity-dot-com>
>
>
>Weazle -
>
>The equation you used apparently is not in the programs Terry has listed
>below.  Where did you find the equation?  Your calcs are correct.  It is
>the equation that is incorrect.
>

<snip>

Hello again John, coilers,

The formulas below are the ones I got from a posting Terry made to 
the list some time ago.  He indicated then, that it was easy to do
the measurements and it gave reliable results, which I agree with.

The mutual inductance is found by:  M = V / (w * I)

Where:  M = Mutual inductance in Henries.
        w = Line freq. in radians per second (377 for 60 Hz.)
        I = The measured current in the primary in amps A.C.
        V = The measured secondary voltage in volts AC.

K can then be found by using the formula:  K = M / sqrt(L1 * L2)

If you look on page 21-2, Fig. 33 in your Tesla Coil Design Manual
you'll see that you have used essentially the same formula.

The only difference is that you use a specific current of 2.65 amps,
while I used 10 amps.  In my case, that meant the measured secondary
voltage (in volts) was divided by 3770 to give the mutual inductance
in Henries.  Having that value, I applied it to the other formula
to get the K factor, just as you show in your manual.