Re: quenching at the first notch

To: "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
Subject: Re: quenching at the first notch
From: Tesla List <tesla-at-stic-dot-net>
Date: Thu, 20 Nov 1997 21:45:27 -0600
Approved: tesla-at-stic-dot-net

From: 	Gary Lau  20-Nov-1997 1718[SMTP:lau-at-hdecad.ENET.dec-dot-com]
Sent: 	Thursday, November 20, 1997 3:31 PM
To: 	tesla-at-pupman-dot-com
Cc: 	lau-at-hdecad.ENET.dec-dot-com
Subject: 	Re: quenching at the first notch

>From: 	kevin[SMTP:wawa-at-spectra-dot-net]
>Sent: 	Saturday, November 15, 1997 7:08 AM
>To: 	tesla-at-pupman-dot-com
>Subject: 	quenching at the first notch
>
>I got these lines from one of the posts
>
>>it definately did not quench at the first notch (don't recall exactly when it
>>was).  I understand that failing to quench at the 1st notch implies multiple
>>pri-sec power transfers and loss of efficiency therein.
>
>
>could someone please explain to me quenching at the first notch, what
>happens when it doesn't, how do you know it's happening, and how you can
>make it so it does?
>
>Thanks
>Kevin Wahila

Since those were my words, I'll do my best, though I'm probably not the most
qualified to say how to achieve this.

Quenching refers to the point in time when the spark gap stops conducting
and consequently, when the primary L-C circuit stops resonating.  Notches
refer to "valleys" in the waveform representing energy in the primary.
In TC operation, when the gap initially fires, primary energy is max,
then decays, as the secondary energy begins at zero and increases to max.
Then the pri and sec energies transfer back and forth, until the gap
quenches, at which point the transfers cease.  Each minimum point in the
primary's energy is called a notch.  Since the goal is to transfer all of
the energy to the secondary (and keep it there), and since each transfer
back and forth between pri & sec looses energy, the highest coil
efficiency is had by quenching on the earliest notch possible.

One can determine at which notch his coil quenches by observing on an
oscilloscope the secondary energy.  Usually one just has to have a scope
probe dangling several feet away from a TC to pick this signal up, no
direct connection is necessary or recomended.  

The hard part is how to get your coil to quench at the first notch.  It
is probably not even possible to quench at the first notch on all coils,
(maybe none?).  Things that affect this are:
1) Coupling between pri & sec coils, as measured by "K".
2) Spark gap geometry and airflow.
3) Power level.
4) The nature of (and if) sparks break out from your top load.

I wish I could be more specific on these points, but this is where my
science fails and black art and luck take over.

Regards,
Gary Lau
Waltham, MA

p.s.  You may wish to look at
ftp://nic.funet.fi/pub/sci/electrical/tesla/pictures/misc/quench.zip for
some simulated pri/sec waveforms