Re: Why does running an NST on an async gap kill it?

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

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <teslalist-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
 >
 > Original poster: "Zagarus Rashkae by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <arbitrarily_random-at-yahoo-dot-com>

 > I think I pretty much phrased the entire question in
 > the subject line :)

A comparison with other kinds of gaps may solve the mystery and find
a possible reason for the (legendary?) problem:

A static gap fires when the voltage is high enough (for the current
gap conditions, essentially temperature), and stops conducting when
the voltage is low enough. The transformer just sees a series of
shortings at its output.

A synchronous gap seeks to align the gaps only when the voltage is
at a given level. The firings are uniformly spaced in time, and
more regular because the gap temperature can be kept lower due to
the fast movement. The gap stops conducting while the electrodes
are still aligned.

With an asynchronous gap, some problems that can happen are:
- Resonance for several cycles without the electrodes becoming
   aligned when the voltage is high enough. This would rise the
   output voltage to too high levels. This is probably the main
   problem, I think.
- Gap firing when the electrodes are just coming out of alignment,
   resulting in forced interruption of the arc when there is
   significant current, causing an energetic high voltage pulse
   across the transformer (this is unlikely to happen, and could
   happen too in a badly adjusted synchronous gap).

 > Is there anything one can to to protect the NST from
 > damage? Wouldn't an RLC filter like a Terry filter
 > protect the NST from spikes?

A filter is surely useful. From the considerations above, an
asyncronous gap that aligns the electrodes more than 2 times
per cycle should be relatively safe.
The worst kind of asynchronous gap would be one that aligns
the gaps one or two times per cycle and runs close to the
synchronous speed, but not there, when the primary capacitor
is dimensioned to resonate with the transformer.

Antonio Carlos M. de Queiroz