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Re: Thyratron pair (was DC Drive)
---------- Forwarded message ----------
Date: Sun, 12 Oct 1997 15:33:47 +0000
From: randy <randy-at-mail.gte-dot-net>
Reply-To: randy-at-gte-dot-net
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Thyratron pair (was DC Drive)
> Date: Sun, 12 Oct 1997 11:58:17 -0600 (MDT)
> To: tesla-at-pupman-dot-com
> Subject: Re: Thyratron pair (was DC Drive)
> From: Tesla List <tesla-at-pupman-dot-com>
>
>
> ---------- Forwarded message ----------
> Date: Sun, 12 Oct 1997 09:02:46 -0500 (CDT)
> From: Richard Wayne Wall <rwall-at-ix-dot-netcom-dot-com>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Re: Thyratron pair (was DC Drive)
>
> 10/12/97
>
> Bert wrote:
>
> snip
>
> >After studying this circuit a bit more, it appears that a this may
> >alsobe a very good way to use a pair of thyratrons for performing
> >quenching experiments or for building an electronic disruptive coil.
> >With this circuit, a conducting thyratron should never see potentially
> >damaging voltage reversals because of the DC offsets. If we design the
> >circuit so that Vpeak of the thyratron is greater than 2xVin, and
> >design it in such a fashion that we ONLY alternately trigger T1 and
> >T2, the approach should work. By varying the trigger pulse width,
> >triggering on any notch could be controlled. It may even be possible
> >to "quench" at any primary current zero crossing. A pair of 4C35's
> >should be able to handle Vin of up to 4 KV, and a pair of 5C22's, up
> >to 8 KV.
>
> snip
>
> >
> > T1
> > Anode |
> > -----------------| | <------------
> > | | |
> > + | |
> > ----- |
> > Vin ----- |
> > - | Cp |
> > | | | Lp |
> > ---------------| |----OOOOOOO-----
> > | | | |
> > + | |
> > ----- |
> > Vin ----- |
> > - | |
> > | | |
> > -----------------> | |------------
> > | Anode
> > T2
> >
> >-- Bert H --
> >
> >
>
> Excellent post. This push-pull configuration has some of the aspects
> of Dave Sharp's new push-pull TC. As we move away from the confinment
> of 60 Hz drivers our technology is elevated to a new plane.
>
> Since a thyratron is only on full blast after it is triggered, perhaps
> big, low impedance vacumm tubes (or IGBTs) might give better control
> than thyratrons. As such, the primary driving waveform can be better
> tailored to the requirements of the resonator. I do not refer to a
> continous wave vacuum tube driver, but disruptive vacuum tube pulses
> that have superimposed information content that the secondary resonator
> requires. Fast pulse rise time and information content of the pulse
> are both crucial.
>
> The vacuum tube or IGBT is pulsed rapidly with superimposed information
> content required by the resonator, but for the most part is quiessent.
> Similar to a spark gap a in on-off time. There is no coil feed back
> driving of the vacuum tube, it's totally electronically driven. BTW,
> SGs contain these two requirements of fast rise time and much, much
> more irrelevant information content and energy that is wasted. If the
> resonator cannot use parts of the wave content, then it simply ignors
> them. The resonator simply chooses what it needs to resonate.
>
> So, why not determine the requirements of a particular resonator and
> design our drivers to provide only these requirements? We may be able
> to exprimentally provide even better waveform content than that which
> occurs naturally.
Although I have yet to build my first coil of any sort, I have been
pondering this very sort of thing, as I have two 4-1000A pentodes
gathering dust. A question that popped into my head sort of
line up with your ideas, I think; drive it with a variable
width and variable frequency pulse.
Another question on my mind is; since we are theoretically
"calling the shots" here, so to speak, is there still a need for
tuned resonance per-se; wouldn''t it be possible to just drive
an autotransformer of more-or less appropriate characteristics
with this set-up, and vary the drive until
everything at the business end of the beast was "happy"?
Or would a cap be necessary for the "ringing", or would
Cstray be enough if this is the case? Maybe pulse-mode
w/o a L/C combination would work, with a weaker streamer?
Two KW of plate dissipation (the 4-1000A's above)
, at maybe 70% efficiency,
at X% duty-cycle could be substantial, I suppose.
> Think about Dr. R's version of the extra coil where he has eliminated
> the driver secondary altogether and drives the extra coil from the
> primary alone. The reason this works is that there is fast rise time
> and the the required extra coil wave content is available.
Now that I have added my two-cents worth above, and we
theoretically got away from the spark-gap, allow me to ask
a stupid question in my typical recidivist way:
Could this pulse (would it have to pass thru a doorknob cap?)
then fire a gap in such a way as to dump voltage from a charged cap
to add more oomph, and then be quenched by a negative-going pulse?
I'm relatively sure that some of Silicon Alley's diodes would have
to be put to use here....
> As we become more familiar with these driving techniques, we will
> eventually be able to elminate the primary/secondary driver altogether
> and directly drive the resonator electronically.
>
>
> RWW
I have been chomping at the bit to build a coil of SOME sort,
but haven't done so due to the fact that I live in an apartment,
second floor. But now I have remembered Randy's First Rule
of Hamfests : Locate the Coke machine. Useful for testing
purposes : "yeah, it worked last time I plugged it in..."
Now to find a gas station with a 220 outlet for the compressor
out back of the building......This may be enough to get me off
my duff.... thanks for your thoughts...Sorry for any mindless
ramblings...
Randy Venable