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Re: TC Inductance Formulas...

> "Baddeley, Glenn" <GBaddele-at-vitgssw.telecom-dot-com.au> wrote:
<snip>
>I have yet to see practical mutual inductance formulae (certainly not
>in BoSC47 or RDH, which I have both) for the case of concentric air core
>single-layer inductors, where the inner coil is a long cylindrical solenoid,
>and the outer coil is in any concentric position in relation to the inner
>and is cylindrical, pancake or conical shape.  (In other words,
>typical Tesla primary/secondary arrangements).
>
>I can approximate the mutual inductance, and know the basic
>integral calculus formula for the general case, but does any one have
>a formula (not charts) for the above case (any of the outer coil
>arrangments mentioned) ?

Hello coilers,
        There is a formula in Grover for mutual inductance computation.
However, it is an approximation, and yields incorrect results for typical
tesla coil geometries.  I wrote a program to compute mutual inductance using
Neumann's formula (basically, a slow numerical integration method).  It
works for a primary with flat pancake, inverted cone, or solenoidal
geometry, and assumes the secondary is a solenoid.  It does not take into
account wire thickness, but this effect is generally small.  
        The nice thing about the program is that one can examine coupling
between the primary and secondary as the coil positions and geometries are
changed.  (It sure beats bending a lot of expensive copper tubing.)  I, too,
wanted to know how the primary interacts with the secondary, and wanted an
answer to the question: Should I use a flat spiral, inverted cone, or
solenoid geometry? 
        I am not ready to post the program to the list at the present time
since it is not particularly user friendly, but I would be willing to run it
for folks on the list.  If you have something in mind, send me private
E-mail and I will let you know what information I need to run a simulation.
Regards,
Mark S. Rzeszotarski, Ph.D.