Re: Optimal Quenching

To: tesla-at-poodle.pupman-dot-com
Subject: Re: Optimal Quenching
From: Tesla List <tesla-at-stic-dot-net>
Date: Wed, 26 Mar 1997 23:00:23 -0600
Approved: tesla-at-stic-dot-net
Subject: 
            Re: Optimal Quenching
       Date: 
            Mon, 24 Mar 1997 20:11:04 -0800
       From: 
            Skip Greiner <sgreiner-at-wwnet-dot-com>
Organization: 
            Greiner, Ltd.
         To: 
            Tesla List <tesla-at-pupman-dot-com>
 References: 
            1


Tesla List wrote:
> 
> Subject:
>             Re: Optimal Quenching
>        Date:
>             Tue, 25 Mar 1997 08:22:39 +1200
>        From:
>             "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
> Organization:
>             Wellington Polytechnic, NZ
>          To:
>             tesla-at-pupman-dot-com
> 
> Hi Skip,
> 
> > Big Snip
> > >     A final note about the MOSFET experiments: anyone (everyone) who
> > > uses either transformers with leakage inductance built-in (neons) or
> > > near perfect transformers (pigs) with "current-limiting" inductors
> > > attached should know that current-limiting applies *only* to limiting
> > > the transformer current in the gap. It has exactly the opposite
> > > effect when charging the primary cap because the two form a resonant
> > > circuit of rather high Q.
> >
> > Malcolm
> >
> > Are you saying that if a cap is "matched" to a neon (ie., a .021uf for a
> > 15kv-at-120ma neon) then it would be possible to charge the cap to the peak
> > neon voltage (or more) more than once each half cycle of the mains. If
> > so it seems to me that our poor old neon will be able to deliver
> > sustantially more power than the nameplate implies?
> >
> >
> > Skip
> 
> No, because time is factored in - the circuit is resonant at a low
> frequency. To get quick charge, the L/C value would have to be
> smaller but then it would no longer be resonant at the mains
> frequency unless both L and C were altered. The problem with neons is
> that you cannot vary the charging inductance. You can vary Cp but
> then the thing is off-tune and current-limiting starts to take
> effect (no longer purely resistive).
>     The current in a series resonant circuit = AC Voltage applied
> in series with it divided by the vectorial sum of the reactances:
> 
> I = V/SQRT(R^2 + (Xl-Xc)^2)
> 
> You can "tune" the charge time to suit a rotary break speed other
> than 2xmains frequency.
>      Here's a phenomenon which demonstrates the resonant nature of
> the charge circuit. I have done this as has Ed Philips and many
> people do it unwittingly. Suppose you choose your cap such that the
> resonant -at- mains condition is met. Then it follows that the circuit
> will accumulate energy (ring up) with each half cycle until the gap
> fires if its Q is greater than 0.5 with dynamic losses taken into
> account. Demonstration: using a static gap set to fire at the
> transformer o/c voltage, turn the variac up part way. The gap will
> fire regularly but at a sub-multiple of the mains due to the
> necessary /half cycle energy accumulation. I think Ed had his gap
> firing at just a 20% variac setting. I have opened the gap on a small
> system such that it fired at fmains rather than 2fmains with a near
> full setting. I could have lost the transformer doing this.
> 
> Malcolm

Hi Malcolm and All

I have a problem with what you outline. Assume a cap value to resonate
at 4x the mains. The cap will certainly attain some max voltage at 4x
the mains frequency. But, that voltage will never get as high as the
voltage would get when the resonance is set at the mains frequency.
Therefore will not the power delivered by the resonance at the mains
frequency be greater than at any higher frequency.

 I hope I said what I think I said.

Skip