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Re: TC Inductance Formulas...


ed-at-alumni.caltech.edu (Edward V. Phillips) wrote:

> Tim:
>         Wheeler's formulas are pretty close for most purposes.

Agreed.

> There
> are more accurate formulas available in such places as Bureau of
> Standars Circular 47 (unfortunately published in 1917 and out of
> print since World War 1) and the publication
> 22 ' "INDUCTANCE CALCULATIONS
> 24 ' WORKING FORMULAS AND TABLES"
> 26 ' 'BY FREDERIC W. GROVER
> 28 '
> 30 ' DOVER PUBLICATION S974
> which your library should be able to produce for you, even though
> it's been out of print for years.  Grover's stuff includes
> formulas good to a part in 100,000.  I have a bunch of stuff here,
> including Basic programs for calculating self and mutual inductance
> of cylinderical solenoids, based on Grover's data and some morfe
> more recent publications.  I would also suggest looking at a
> copy of the "Radiotron
> Designer's Handbook"   (sorry, can 't keep my finger off the
> return key) which your library should also be able to produc e.
> Ed Phillips

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) ?

'a part in 100,000' is way over the top, a part in 100 is satisfactory
for on-paper design work, where other factors (power related,
skin effect, physical construction etc) may have an influence of
this order, or greater.

Glenn Baddeley
Melbourne, Australia