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Re: Arc Impedance Study - Computer Models

At 04:33 PM 10/11/98 -0600, you wrote:
>to: Sam
>
>Definitely not.  In most all systems the sec. first turn should be elevated
>above the pri by 1 to 1 1/2 inches.  We use up to 9 inches in some of our
>larger systems.  The idea is to set the coeff. of coupling so the double
>"Camel's hump" doesn't occur which would indicate frequency splitting and
>the division of energy into two separate freqs which then start "beating"
>against each other.  You need a pulse generator or signal generator and a
>scope to see the double hump, but as the sec is elevated the two freqs will
>come together and this is the point for most efficient energy transfer and
>good operational characteristics from the coil system.
>
>DR.RESONANCE-at-next-wave-dot-net
>
>
Hi Dr. Resonance,

Hmmmm....  I guess I disagree with that.  My coil, with a coupling of 0.17,
has two very distinct spectral humps at ~100 and ~119 kHz.  Indicating it
is way too over coupled by the signal generator test you mention.  This
double hump is a result of the primary and secondary energy bouncing back
and forth in the typical multiple notches wee see.  In order to get the
coil to operate so that the coupling produces a single notch, I would have
to lower the coupling to around 0.07.  This would produce a single notch
and give a single hump in the energy spectrum.  However, the power
delivered to the load would be very low.  
	I think lowering the coupling to produce a single hump may have sounded
like a good idea back when we had little real data about what is going on.
But that theory did not take into account that we are trying to deliver
substantial power to a complex load.  Thus, we need much higher coupling to
push much more power into the secondary than the low loss signal generator
tests and theories behind it would suggest.


To answer Sam's original question... I have found it extremely useful to
adjust the secondary height in order to adjust coupling.  John C. tries to
do this with secondary to primary spacing but this is not very adjustable
once the coil is built.  I like to make the clearance close and then adjust
the height so that I have a full range of couplings to choose from.  I can
then find just the right height and coupling for best performance.

	Terry Fritz