Re: Quenching

To: "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
Subject: Re: Quenching
From: Tesla List <tesla-at-stic-dot-net>
Date: Wed, 10 Sep 1997 18:51:21 -0500
Approved: tesla-at-stic-dot-net

From: 	Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: 	Wednesday, September 10, 1997 2:56 PM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: Quenching

Hi John,

> From:   FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
> Sent:   Wednesday, September 10, 1997 5:53 AM
> To:     tesla-at-pupman-dot-com
> Subject:    Re: Quenching
> 
> I<< snip>   Without going through all the steps, I finally tried the air jet 
> > at full pressure. Now the gap was very loud and bright, output had 
> > sunk to a real low, and I actually achieved quench at the end of the 
> > second ringup with no breakout. It is clear this was a totally useless 
> > setting because while the quench looked excellent on the scope, the 
> > gap was dissipating the bulk of the power. This was borne out by the 
> > abysmally short discharge to the ground wire. BTW, the full air jet 
> > was so violent the spark was considerably displaced from the centre 
> > of the gap electrodes.
> 
> Malcolm,
> 
> By second ringup, do you mean the second notch; the second
> complete transfer of energy to the secondary?  If so, this should
> be the perfect place to quench I would think.  Could it be that some
> firings were being skipped, or missed?  Could this be what some
> people refer to as "overquenching"; the gap is sometimes prevented
> from firing due to excessive air?

That is what I mean. The results spoke for themselves. The gap was 
loud, bright, and chewed up well over half the cap energy like 
this. I conducted those tests single shot. The repetitive results were 
no better. Output voltage dropped by over half at maximum air blast.
I now use relative brightness/noise between primary and secondary 
discharges as a good guide to efficiency.

> > of quench he was having to apply to stop power arcs was hindering the 
> > output of the coil. It seems to me that the way around this is to 
> > choose a bigger cap to load the supply more heavily so the air supply 
> > could be moderated to the point where it served the tuned circuits 
> > best.
> 
> I have so rarely seen power arcs in my TCs, that its hard for me to
> comment.  I agree large caps should help prevent the power arcing.

The real problem became clear last night. The primary voltage is just 
too low to allow the gap to fire reliably with any airblast at all.
My next move will be to run with a smaller primary capacitance, more 
primary turns to maintain tune, and higher primary voltage. While
my output voltage won't improve if Ecp remains the same, it should 
get reliable gap firing and raise the primary Q in one hit.

> >     For my coil it looks as if a quite moderate air jet is best for 
> > tuned circuit behaviour. Question is: will it also be best for 
> > stopping transformer arcs in the gap? If more air is required to stop 
> > the arcing, it seems I could do better in matching the primary cap to 
> > the transformer. Be interested in comments anyone else has to make on 
> > this.
> 
> By using 120BPS sync gaps and resonant charging,  the gap fires
> at or near the zero crossing point of the 60Hz AC cycle, and power
> arcs are unlikely.

Agreed! Perhaps it is time I went to the rotary. But I still think I 
can do a lot better with static gaps under the conditions above.

Malcolm