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Re: Optimal Quenching Tests

Tesla List wrote:
> 
> Subscriber: FutureT-at-aol-dot-com Sat Jan 11 10:52:21 1997
> Date: Fri, 10 Jan 1997 16:38:50 -0500 (EST)
> From: FutureT-at-aol-dot-com
> To: tesla-at-pupman-dot-com
> Subject: Re: Optimal Quenching Tests
> 
<Mucho-Snippage>

> Bert,
> 
> Thanks for the speculations, and thanks also for the info in your other post
> answering my Q measuring questions.  I've been doing some speculating also:
> 
> 1)  Are the PSPICE conclusions really refering to splitting, could they be
> refering to beating?  Splitting can eventually lead to beating.   I can see
> how 1st notch quench would eliminate beating because the primary would
> contain only 1/2 of a beat period, and the secondary would also contain 1/2
> of a beat period.   I agree that for beating to occur, energy must make a
> round trip, as you said, energy flows only one way if we quench at first
> notch--therefore no beating.  But I think we still get splitting.  I don't
> know if this splitting can cause racing sparks.

I originally thought the same, John. However, when I do a Fast Fourier
Transform for the case where the primary is optimally quenched or
before, niether the primary and secondary voltages or currents show any
evidence of any frequencies other than the fundamental of the
secondary/toroid. 

> 
> 2)  Did the old spark transmitter engineers really say that 1st notch quench
> eliminated splitting, or did they say it eliminated beating?  Maybe they just
> looked at their secondary waveform and said, " look, a  nice clean
> ringdown....no beats....just what we want!"    Also, in Richard Hull's
> comments on the subject, was he refering to splitting, or to beating?   Are
> we differing on our definitions of terms?

I don't think so... they were probably striving also for spectral purity
and output efficiency. However, I'll have to defer to Ed Phillips or
Richard Hull, since they originally mentioned this in earlier posts.
However, isn't the beat frequency the difference between the upper and
lower "split" frequencies? These "sidebands" actually are not there 
until AFTER the first energy transfer - all that's seen IS the
fundamental frequency of the high-Q secondary circuit. 

> 
> 3)  I agree that a key point is the one way transfer of energy from the pri.
> to the sec.,  Once the energy makes round trips, undesirable phase shifts and
> beating wreak havoc by creating unwanted frequencies, which result in racing
> sparks.
> 
> 4)  I think the first notch is caused by the additive effect of the two split
> frequencies; at the point when they are 180 % out of phase--they cancel and
> cause the notch.  Also, since the energy in the secondary is out of phase
> with the primary, the secondary is now at it's maximum energy level.

That's what I thought originally - however, if there were two
frequencies then wouldn't these should show up in the FFT analysis, and
in peak/zero crossings of the primary versus secondary voltage
waveforms? During the first primary:secondary energy transfer, there are
no split frequencies, nor any relative phase shifting. But they do
appear afterwards if the gap is still firing... Wierd!!

> 
> 
> > haven't taken the speculation past this point... However, "classical
>  >theory", observation, and PSPICE all show that frequency splitting will
> >occur beyond this point (once energy flow reverses).
> 
> 
> Again, I think splitting always occurs in an over-coupled, double-tuned
> circuit, but beating can be eliminated by quenching at the first notch.
> 
> >Flames, brickbats, etc. are welcomed!
> 
> >-- Bert --
>   >>
> 
> Are we "splitting hairs", and "beating" our brains?  All comments are
> welcomed.
> 
> John Freau

Probably... :^)

Anyways... the _practical_ Bottom Line I think we CAN agree on: 

For k = coupling coefficient  
    Fs = the resonant frequency of the secondary/toriod

Then:
Quench at, or near, 80-85% of 1/(2kFs) for maximum energy transfer and
retention by the secondary (no matter the actual mechanism involved!)
:^)
This should translate to maximum energy transfer efficiency, and I
suspect, maximum spark length.  

Safe coilin' to you!

-- Bert --