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