Re: Dwell time, etc

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: FutureT@xxxxxxx 

In a message dated 4/1/06 3:24:31 PM Eastern Standard Time, 
tesla@xxxxxxxxxx writes:


> Hi John,
>
> I calculated the dwell time on my 8 inch 1800rpm SRSG with four 1/8"
> flying electrodes and thought the dwell time was like 3 or 4 times
> the energy transfer time.  This seemed long enough for energy to flow
> back into the primary and reignite the gap.  However, it also seemed
> like if a breakout occurs, the energy is quickly removed from the
> secondary so dwell time would not be a problem.  Is this correct
> thinking or did I make an error somewhere??
>
> Gerry R.


Gerry,

There may be two types of re-ignition.  One type is caused by the
energy flowing back into the primary to re-ignite the gap.  This
is the type you mentioned.  This type is actually *OK*, because
it's not due to the capacitor being recharged by the power supply
and then re-igniting.  Instead it's being caused by energy which is still
ringing down in the system.  I'm not even sure if the gap
really quenches between transfers within the same "bang".
Enough residual energy and ions may be around to keep
the air ionized.  I'm not sure.  Very few coils quench for good on the
first energy transfer or "first notch".  Larger coils have an
easier time quenching on the first transfer.  For example
Ed Wingate's large magnifier TC quenches at the first transfer
when running at full power, but not at low powers.  This is
despite his mechanical dwell time being about 3 times the
energy transfer time.  Small coils generally quench on the
3rd notch when using a rotary.  Sometimes on the 2nd notch
or transfer.  The question is still open regarding whether there's
any spark length advantage to quenching on the first transfer
vs. the 2nd or 3rd transfer.  Bert Hickman often explained
that the extra transfers may actually help the spark to grow,
although this may be negated by other factors in certain
cases.  More work needs to be done in this area.  Maybe
the solid state coilers have some comments on this?
(The longer time to quench gives less time for the cap to charge,
so that's a negative factor.)  Generally spark breakout doesn't
load the coil enough to give 1st notch quench except on
large coils.  But certainly without any breakout many
transfers will occur.  Ground strikes however do drain the energy
out of the system very quickly.

The second type of re-ignition (the bad type) is when the
energy has rung down, then the power supply charges
the cap to a high enough voltage to fire the gap while
the electrodes are still aligned.

Some of the terminology makes it a little difficult to
make things clear.  The terminology is not always well
defined in Tesla coil matters in general.

John