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RE: Mutual inductance and K factor
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>"
>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.
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.