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Re: Overcoupling?

At 09:35 AM 5/6/99 +1200, you wrote:
snip...
>> Frequently I see the term "overcoupling" in this list, but can't see
>> what it means. I don't see a reason for increased voltage gradients
>> along the secondary just because the coupling coefficient to the
>> primary is increased. A primary closer to the secondary would induce
>> sparking between the two coils, certainly, but why sparks along the
>> secondary? Would not this effect be due to tuning to a higher order
>> resonance mode instead?
>> 
>> Antonio Carlos M. de Queiroz
>
>Three things I can think of:
>- the voltages do get higher at certain values of k as the energy is 
>transferred much more rapidly giving the gap less time to lose it.


Yes, but other factors may begin to limit the voltage too but this is
certainly an excellent area to look at.  See my other response to Reinhard
on this subject for more details...
 

>- closer proximity of the primary to the secondary encouraging corona 
>formation around the secondary, particularly with raised primaries 
>such as conical or helical (I've seen this in small systems)


Another possibility, but I think arcs occur in systems that don't seem to
have high field stress do to corona.  Such as the long thin coils of old or
out of tune coils that seem to like to arc at the base despite the fact
that the output voltage of the coil is very low.


>- excitation of spurious resonances causing the secondary to be 
>electrically shortened because of the presence of the upper sideband.


That is possible,  However, that is certainly the most complex and messy
mechanism that could be at work.  So far I have found that the simplest and
most straight forward possibilities turn out to be the correct ones.
However, if all else fails this could be a place to look.  Measurements can
see these harmonics effects and they show up in models but I doubt at this
"moment" that they are responsible for racing arcs.  Although, ring up
times do decrease and that can lead to inducing all kinds of fun things...


>I finally had to accept that this is a possibility after Terry's 
>current msmt results, much as I don't like the idea. Perhaps this is 
>a field ripe for further measurement and exploration to see which 
>of the above is correct.
>
>Malcolm
>


Exploration is why we are here!  Perhaps we can formulate some experiments
to prove/disprove this.  Perhaps we can just think through some too...

	Terry