Re: More Coupling...

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

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-uswest-dot-net>" <bert.hickman-at-aquila-dot-net>

Tesla list wrote:
> 
> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<paul-at-abelian.demon.co.uk>
> 
> Bert Hickman <bert.hickman-at-aquila-dot-net> wrote:
> 
> > ACMI Results versus measured values:
> > ===================================
> >
> >                    ACMI:        Prev. Measured:          Error:
> >                    ====         ==============           ======
> > Pri Self Ind       168   uH     161.8 (-at- 15.625 Turns)      -
> >                                 Est 170 uH at 16 Turns    -1.2%
> > Sec Self Ind        74.0 mH      73.5 uH                  +0.6%
> > Pri-Sec Mut Ind    708.8 uH     not directly measured       -
> > Coupling Coeff.    0.201         0.209                    -3.8%
> >
> > The results appear to be within the estimated accuracy of my
> > measurements.
> 
> Thanks for the results Bert - they are comfortably within the
> tentative limits I might guess for acmi accuracy. The success with
> primary windings is pleasing - I had in mind the possibility that
> with the thick conductors typically used, I might have to integrate
> source current filaments over the volume of the conductor. The
> likelihood of this seems to be dwindling and we seem to be able to get
> satisfactory predictions by assuming that all the primary current is
> concentrated in a filament at the wire center. Interesting that your k
> factor measured at RF agrees with the value calculated for low
> frequency - it appears that neither the skin effect, nor the non-
> uniform secondary current are interfering with the coupling enough to
> be troublesome at this precision. Could it be that your slightly
> higher k factor at RF is due to the secondary current bias towards the
> low end of the coil?
> 
<SNIP>

Paul,

I did use the centerlines for the 3/8" copper for the primary's
parameters for ACMI - apparently, skin or proximity effects appear to
have a negligible effect on the filamentary inductance calculation in
ACMI versus reality. 

The K measurement was done with a fairly heavy topload in place.
However, based upon the relative imprecision of the measurement
technique (measuring the sideband peaks versus Fo and back computing K),
I would assume that my K value is probably only accurate to within +/-
5-7%, so I really wouldn't put much stock in the fact that my measured K
seems to be on the high side. 

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com