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Re: Quenching question.



Original poster: FutureT-at-aol-dot-com 

In a message dated 3/7/04 4:05:05 PM Eastern Standard Time, 
tesla-at-pupman-dot-com writes:

>So do we want a gap that quenches real fast or do we want a gap that
>quenches at just about the right amount of time?  We seem to go for a gap
>that quenches very rapidly.  Could that be only because we can't get one to
>quench fast enough yet, let alone one that quenches too fast?
>
>Thanx
>
>Luke Galyan


Luke,

We want the gap to quench at the right time which is after all
the energy has been transfered.  Yes, It's very hard to get a fast
enough quenching (more below).  The best quenching is considered
to be at
the first notch, which is when all the energy has transfered from
the primary to the secondary.  This traps all the energy in the
secondary and the energy is all available for producing long
sparks.

Although we want fast quenching, there is usually no advantage
to obtaining fast quenching at the price of increased losses.
We can certainly improve the quenching by increasing the
losses, because energy is then frittered away more quickly,
causing the gap to quench.  The gap will always tend to quench
when the system runs out of energy from a bang.

Usually the quenching is a tradeoff between good quenching
and reasonable losses.  Quenching can be improved by loosening
the coupling, but this increases the losses because energy is
transfered slower thereby giving more time for losses to occur.

It is not known for sure that first notch quenching gives any
advantage.  There is some evidence that second notch
quenching may be as good or better.  This is because each
increase in RF envelope energy (each rise), tends to cause
the sparks to grow longer.  Bert H. has written extensively on
this subject.  Therefore the two rises which occur with second
notch quench may actually propel the spark further.  However
when the energy makes these round trips from pri to sec to
pri and back to the secondary, losses occur during this time.
These losses my negate any advantage of the two spark
growth periods offered by second notch quench.  In reality,
there is probably not much difference in performance between
first notch or second notch quench.  Many smaller coils
quench on the second or third notch (the notch shows up
in the energy transfer  waveform in case you're wondering
what *notch* means here).  Larger coils may quench better
because they tend to run at a lower frequency which causes
the notches to be wider in duration for a given k value.  A
wider notch gives the ions more time to disappear.

My old research coil which gave 42" sparks quenched on
the 2nd notch most of the time if I remember correctly.

One reason why using a large number of turns on a small coil
may increase the efficiency is because it improves the quenching by
lowering the frequency and giving the ions more time to
disassociate.  A large coil will tend to run at a low frequency anyhow,
so a great number of turns may not be as important.

Some coils such as Ed Wingate's magnifier quench on the
first notch.

John