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Re: Triggered spark gaps for coils
Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jimlux-at-earthlink-dot-net>
Xenon flash lamps are a triggered spark gap, but are probably unsuitable for
TC use for the reasons you mention:
1) Slow quench
2) difficult cooling
One of the new xenon filled short arc lamps (as used in all sorts of things
like car headlights) might be a more likely candidate, since at least they
are designed to dissipate a fair amount of heat from the envelope.
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, March 17, 2001 8:47 PM
Subject: Re: Triggered spark gaps for coils
> Original poster: "Metlicka Marc by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <mystuffs-at-orwell-dot-net>
>
> bert, Gary, all
> i to have been giving this some thought. i was actually looking at the
> triggered xenon flash lamp as the source of the gap.
> if you've ever noticed them, they have the trigger electrode dead center
> between two tungsten points and are filled with the gas. it is built of
> heavy pyrex or something like quartz so cooling could be overcome.
> the one i had here met a sorrowful death under my cordless drill, but i
> see them come up on ebay once in a while. i don't think one would quench
> because the gap is only about an inch, but maybe three or four in series
> with only the first one as the triggered unit?
> or am i not understanding the xenon properties correctly? kind of a real
> poor mans triggered gas spark gap?
> marc
>
> Tesla list wrote:
> >
> > Original poster: "Bert Hickman by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <bert.hickman-at-aquila-dot-net>
> >
> > Gary and all,
> >
> > Hmmm... I was wondering why you just outbid me on that pulse
transformer...
> > :^)
> >
> > I think it makes great sense! There should be no reason that you
couldn't
> > use a three terminal gap (such as a home built or commercial field
> > distortion gap) to perform this task as long as you provided a flow of
gas
> > through the gap to help cool it and remove ions. In fact, field
distortion
> > gaps were often used to provide rapid pulsed switching for flashlamps to
> > drive older pulsed excimer lasers prior to their replacement by hollow
> > anode thyratrons (which will safely handle a degree of oscillatory
> > bi-directional current flow). For example, older Lumonics pulsed lasers
> > used field distortion gaps that looked a lot like little Claymore mines
> > (about 5.5" in diameter, and 3" thick) - every now and then these come
up
> > for sale on Ebay.
> >
> > You need to make sure that the middle electrode is centered between the
two
> > main electrodes and that is biased so that its potential is halfway
between
> > the voltage that's applied between the main electrodes (except for when
you
> > want to "fire" it). One way to do this is to use a pair of HV resistors
to
> > create a voltage divider. Triggering is done by coupling a HV pulse
(from
> > an ignition coil or a HV pulse transformer) through a blocking
capacitor.
> > The main gap spacing is adjusted such that the gap will self trigger at
a
> > voltage that's at least 20% higher than the maximum expected voltage
from
> > the HV supply. The triggering voltage needs to be at least half of the
> > maximum applied gap voltage in order to reliably force breakdown. A LV
> > pulse capacitor, SCR, and phase shifting circuit operating off fullwave
> > rectified line voltage can then be used on the LV side of the trigger
> > transformer to control the trigger point in a manner similar to
adjusting a
> > SRSG via a variac/capacitor phase shifter. Use a fixed font in order to
see
> > the diagram below:
> >
> > To HV1
> > |
> > | ||
> >
|----------------------o----------------||-------------
> > | | || Ctank
|
> > | |
|
> > | |
|
> > _ | |
|
> > | | | ------------------
|
> > __| |_ R --/\/\/\/--- | Main 1 |
O
> > HV | ----------------
O
> > Trigger C1 || |
O
> > Ltank
> > --------------||-----o--------------------- Trigger Electrode
O
> > || |
O
> > | ----------------
O
> > R --/\/\/\/--- | Main 2 |
O
> > | ------------------
|
> > | |
|
> > C1 | |
|
> > | |
|
> > | |
|
> >
|----------------------o--------------------------------
> > |
> > |
> > To HV2
> >
> > -- Bert --
> > --
> > Bert Hickman
> > Stoneridge Engineering
> > Email: bert.hickman-at-aquila-dot-net
> > Web Site: http://www.teslamania-dot-com
> >
> > Tesla list wrote:
> > >
> > > Original poster: "Lau, Gary by way of Terry Fritz
<twftesla-at-uswest-dot-net>"
> > <Gary.Lau-at-compaq-dot-com>
> > >
> > > >From my recent web searches and technical paper readings, there
appears to
> > > be a large variety of commercially available 3-terminal triggered
spark
> > > gaps. And it seems that these can easily be home-made as well. These
> would
> > > seem to be ideally suited for use as replacements for rotary spark
> gaps, but
> > > I've not been able to find any reference to this obvious application.
The
> > > only reference I've seen towards "amateur" applications is in can and
> > > quarter shrinkers. While RSG's do have relative simplicity on their
side,
> > > it seems as though there ought to be some worthwhile benefits to using
a
> > > triggered static gap. Has anyone attempted this? Or am I attempting
to
> > > invent a square wheel?
> > >
> > > Gary Lau
> > > Waltham, MA USA
>
>
>