Re: [TCML] Re: Position of baffle inside secondary

[Paul Nicholson <tcml88@xxxxxxxxxxx>]

Dex wrote:

> Could it be after all that current computer models overlook
> something regarding propagation of higher overtones and their
> interaction even without spark loading?

Yes, certainly.   Computer models are checked against
measurements taken from a real coil which is operating below
breakout.   Typically a base current waveform is captured
and compared with the waveform predicted by the model for
that particular coil.

But only a handful of such comparisons have been made, for
example here

 http://abelian.org/tssp/tfss270501/

What we're looking for is a correspondence, not just of
the basic beat waveform, but also the little ripples on the
waveform which are the overtones.

Here's a more interesting one which demonstrates something
that has not been modelled,

 http://abelian.org/tssp/md110701/

Overall a good correspondence between model and measurements,
but scroll down to the first 20uS graph.  Note the high level
of initial HF ringing, caused by overtones of the primary
which were not calculated by the model.  These decay rapidly
but are initially quite intense.    It is not known what
happens when one of these primary overtones coincides in
frequency with a secondary overtone.  Would that induce
short-range breakdown voltages along the secondary?  Small
changes in k would alter the relative tuning of the overtones,
making such behaviour quite k-sensitive.

Changing topic slightly - the voltage max can be moved into
the coil (instead of at the top) if the discharge 'load' has
an impedance less than the characteristic impedance of the
coil+topload combination.   This would be a transient
situation because while it is happening, stored energy is being
dumped into the load very rapidly - the overall Q is virtually
destroyed.  A sudden switch into this 'half-wave' mode sends
a transient along the coil - somewhere I have an animation of
it, which could in principle generate a brief, very high volts
per turn as the leading edge of the transient propagates
down the coil.

But all this is guesswork based on insufficiently qualified
models. Plenty of research remains to be done.  There are many
more questions than answers.
--
Paul Nicholson
--

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