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Spark Gaps


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From:  Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent:  Wednesday, April 15, 1998 12:34 AM
To:  Tesla List
Subject:  Re: Spark Gaps

Hi Richard (Hull), all,

> From:  richard hull [SMTP:rhull-at-richmond.infi-dot-net]
> Sent:  Sunday, April 12, 1998 5:05 AM
> To:  Tesla List
> Subject:  Re: Spark Gaps
> 
> At 08:33 PM 4/11/98 -0500, you wrote:
> >
> >----------
> >From:  Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
> >Sent:  Friday, April 10, 1998 10:25 PM
> >To:  Tesla List
> >Subject:  Re: Spark Gaps
> 
> >Thratron or transistor switches were used by Richard Hull and Malcolm
> >Watts respectively to switch off primary current at earlier current
> >"zeros" (of the coil's fundamental operating frequency) during a number
> >of very interesting quenching experiments last year. Malcolm's attempts
> >to turn off a low-power transistor-switched primary circuit at points
> >other than primary current zeros did result in the expected high voltage
> >spikes stemming from rapid di/dt, but it's not clear that the an arc's
> >characteristics will permit this to actually occur under any reasonable
> >circumstance in higher power air-gap systems.
<snip> 

> FETs are really a great way to get data, but are in the tit-mouse class at
> their best. There are a lot of solid state items coming along now that can
> give the H2 thyratron a run for its money when comparing raw specs but the
> heavy kick back found in tight coupled Tesla systems will leave the solid
> state devices a smoldering mass while the H2 thyratron keeps on ticking.  In
> addition some these new solid state devices are in the kilobuck price range.
> Great stuff to dream about though.

Absolutely agree. The coil eventually produced discharges reaching 
about 1/2" FWIW. The main aim of the exercise was to get sub-uS 
control of frequency, dwell and quench times to examine the issues 
involved in detail. I felt it was reasonable to extrapolate the 
results to other disruptive systems given that they basically work 
the same way. Very interesting, very instructive and hopefully 
very useful when I come to try using those kA range SCRs I mentioned 
a while ago. I do not want to send them to an early grave. 

Regards,
Malcolm

> No, it looks like we are stuck for the foreseeable future with air gaps and
> their limited control.

Unfortunately yes. 

> Richard Hull, TCBOR