Re: Dwell time, etc

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: FutureT@xxxxxxx 

In a message dated 3/28/06 7:27:25 AM Eastern Standard Time, 
tesla@xxxxxxxxxx writes:


> What is dwell time and how does it affect your coil?


Kevin,

Mechanical dwell time is the time duration during which the electrodes
are aligned.  The thicker the electrodes the longer the dwell if
everything else stays the same because there is more distance
for overlap of electrodes.  Luckily dwell time is usually not
an issue for the standard electrode diameters, rotor diameters,
rotor speeds, and breakrates commonly in use.  After the gaps
fire, the capacitor will discharge and the energy will be used up.
When there's no longer enough voltage to jump the gap, the
gap will quench.  Typically the gap does not quench because
the electrodes pull apart and break the spark.  Rather the
electrodes may still be aligned when the gap quenches.
This is because the cap runs out of energy and the voltage
drops until quench occurs.  A rotary gap determines when
the gap will fire, but not when it will quench.  Quenching is
more determined by other aspects of the Tesla coil although
teh gap does have some effect.  For example if the electrodes
run too hot, they'll take longer to quench.  If the dwell is really
long in duration, then the cap may charge up enough to
jump the gap while the electrodes are still aligned.  This
causes very inefficient operation, but again this is rare.  It
would require a low rpm motor with very thick electrodes,
and a small diameter rotor along with a rather small capacitor
value.  For the most part mechanical dwell can be ignored
with the caveats I mentioned above.

I only recommend using fixed static gaps in addition to the
rotary if they seem to be needed.  Usually they're not needed,
but may be needed at very high powers, etc.  I like to keep
my coils as simple as possible whenever possible.

   http://hometown.aol.com/futuret/page3.html

John