Loading, quenching, and surging

To: "'Tesla List'" <tesla-at-pupman-dot-com>
Subject: Loading, quenching, and surging
From: Tesla List <tesla-at-stic-dot-net>
Date: Fri, 6 Mar 1998 23:01:20 -0600
Approved: tesla-at-stic-dot-net

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From:  FutureT [SMTP:FutureT-at-aol-dot-com]
Sent:  Friday, March 06, 1998 8:04 AM
To:  tesla-at-pupman-dot-com
Subject:  Loading, quenching, and surging

All,

Many have discussed the importance of spark loading for good quenching,
and I think my latest coil demonstrates this is an intriquing way.  I'm using
a two gap sync rotary at 60 BPS, and obtaining 45" sparks at 600 watts.

Often the sparks are shorter than 45", and at these times, the gap arcs
are very bright indicating poor loading and subsequent poor quenching.
Then as the coil runs, a random spark often reaches out a little farther,
which causes the loading to improve, which improves the quenching,
making the gap arcs dimmer.  As the quenching improves, the extra
energy going into the arc lengthens it even more, which in turn improves
the loading and the quench.  So a positive feedback condition is occuring
which eventually propels the spark out to the full 45", and the gap arcs
are very dim by this time, indicating excellent quenching.  Finally, the 
spark hits the measuring wire, the loading is adversely affected, and 
the gaps brighten, and the process is free to begin again.  In addition,
the longer sparks may be improving the tuning of the coil, adding still
another factor to the positive feedback loop.  The loudness of the coil
also increases during the long spark, good quenching times, reflecting
the extra energy going into the streamers.

This process may be occuring in many coils, but may not be so
pronounced.  It is possible that the 60 BPS break rate slows the
process so it is more easily seen.  It is also probably important to 
use a somewhat marginally quenching gap to make the process more
noticeable.  I've noticed that when I use better quenching series rotaries,
the gap tends to run at a more constant brightness, and the sparks tend
to be more equal in length with less surging.  I actually find the surging-
type operation gives a more interesting and impressive display, and some
visitors who saw the coil in operation strongly agreed.  I've noticed that
many large coils tend to surge in this way.  Maybe the characteristic
is enhanced in large coils, or maybe the quenching was marginal in
those coils.  I think this surging effect is at least a partial explanation
for those *rare long sparks* that people refer to.

I've seen this surging in some of my previous coils, but to a lesser
degree. I'd be interested to hear if anyone has seen this effect in
their coils.  Comments welcomed as always.

John Freau