# Re........ Measuring Coupling Coefficients

```
From: 	John H. Couture[SMTP:couturejh-at-worldnet.att-dot-net]
Sent: 	Tuesday, December 09, 1997 2:01 AM
To: 	Tesla List
Subject: 	Re........  Measuring Coupling Coefficients

At 04:59 AM 12/8/97 +0000, you wrote:
>
>From: 	terryf-at-verinet-dot-com[SMTP:terryf-at-verinet-dot-com]
>Sent: 	Sunday, December 07, 1997 7:01 PM
>To: 	Tesla List
>Subject: 	Re........  Measuring Coupling Coefficients
>
>All,
>        Mark's program will be a major benefit to those who do Tesla coil
>modeling.  The mutual inductance between the primary and secondary coils has
>always been a very difficult factor to predict. This will provide one of the

>--------------------------------------------------- snip

I agree that Mark's program will be a major benefit to TC design.
Hopefully it will eventually be incorporated into a comprehensive program
that will calaculate all of the necessary TC parameters and automatically
keep them in tune when changes are made like the JHCTES program. The more of
these programs that become available the better for coilers.
JHC
----------------------------------------------------- snip

>The equation Q = 6.283 F L does not sound correct.  The equation 6.283 F L
>is equivalent to the inductive reactance of a single coil, not it's Q.

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

You are correct. The equation should be   Q = 6.283 F L / R
The Rp and Rs are related to mutual reactance by  Xm = sqrt(RpRs).
JHC

-------------------------------------------------------- snip

The equation ( K = >1/sqrt(QpQs) ) will predict a K of 0.0527 but does not
take into account
>that the two coils are separated by 150 feet and thus have a K of zero.

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

The K - 1/sqrt(QpQs) is for mutually coupled coils so the K would not be
zero.
As Q depends on F it would appear that coupling depends on frequency. I
havn't seen an explanation for this contradiction with other K factor equations.
JHC

------------------------------------------------------- snip

>I disagree that the energy transfer is 100%.  Resistive losses, as you point
>out, are at work and the losses as sparks emit from the coil disrupt the
>circuit and can cause heavy losses of efficiency.  Models take such

------------------------------------------------------- snip

Transfer of electrical energy by currents will cause losses. Transfer of
electrical energy by the magnetic fields created by currents is always 100
percent because this is by induction which is reactive. Refer to H.H.
Skiling's Transient Electric currents. Coupling (K factor) only affects the
time to make a complete transfer.
JHC

------------------------------------------------------snip

I agree that measuring or calculating the mutual inductance of Tesla coils
is important. The typical accuracy of +/- 5% or 10%  is usually sufficient
at the design stage and for testing.
JHC

------------------------------------------------- snip

>The great thing about Mark's program is that is should be able to handle any
>configuration.  I believe that the JHCTES program is based on coil testing
>of a limited number of coils in limited configurations and numerical
>predictions are based on those data points.  This should give good results
>as long as the coils in question are similar to the original coils.  Mark's
>program should even be able to do the non-linear coils I play with (needs
>slight modification).  The JHCTES program cannot predict these coils at all.

----------------------------------------------------- snip
>        Terry

I have not seen Mark's program so cannot comment on its ability to handle
any configuration.
The JHCTES program  is for classical Tesla coils only and not for non
classical type coils.
The JHCTES is based on theory and empirical data from real coils. This
data was converted into equations a computer could use by using mathematical
regression methods. This means the program covers a wide range of original
coils and all coil designs in between. Many successful coils have been
designed and built using this program.

John Couture

```