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Measuring where quench occurs (fwd)



---------- Forwarded message ----------
Date: Sun, 28 Sep 1997 14:27:45 -0600 (MDT)
From: Chip Atkinson <chip-at-pupman-dot-com>
To: tesla-at-pupman-dot-com
Subject: Measuring where quench occurs

From: 	Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: 	Thursday, September 25, 1997 4:39 PM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: Measuring where quench occurs

Hi Jason,
 
> From:   Jason Judd[SMTP:Jason.Judd-at-anu.edu.au]
> Sent:   Wednesday, September 24, 1997 11:01 PM
> To:     Tesla List
> Subject:    Measuring where quench occurs
> 
> Hi all,
> 
> I have recently been watching waveforms of my coil on a scope. The scope is
> set up about 8' from the coil with a short wire on the end of the probe. I
> clearly see two notches and then a very slow low amplitude decay. By
> varying K the number of rings in each notch changes ( of couse ), but what
> am I actually seeing here does this show that the gap is quenching after
> the second notch ? I wouldn't have thought so because the secondary will
> continue to ring until the energy has been disipated ?

The peak of each "bump" is the point at which pri-sec transfer is 
complete. So if you see two bumps with a null after each and then
a third one which doesn't null but decays slowly, your gap is 
quenching at the completion of the third transfer. By that time, 
energy in the secondary is so low it doesn't significantly 
contribute to the output discharge. The quench occurs when gap current
and voltage is too low to sustain athe gap discharge.  

> My tests have been carried out at low power levels so far, but I found that
> when I turned up the power sometimes I would see a third notch.
> 
> Do other people measure the quench by directly measuring accross the gap ?

I just observe the secondary waveform. Much easier. The primary humps 
are much the same, simply offset by 90 degrees. When you see an extra 
notch/hump, the output discharge is not as strongly ionized so energy
remains sloshing around in the coupled system for longer.

Malcolm