Re: 304tl

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Brett Miller <brmtesla2@xxxxxxxxx>


--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: Sparktron01@xxxxxxxxxxx
>
> SNIP
>
> This reminds me.  I had an idea.  What about using
> an
> interrupter with a suitable SCR, with some good
> isolation between the SCR and the interruptor.
>
---------------------------------------------------------------
> Brett
>
> You need to use a controlled switch like an IGBT,
> a SCR will require cathode current to drop below
> latching current values (i.e. a current '0') to
> allow
> the current to be controlled.  An IGBT can pretty
> much be turned on and off as necessary, as long as
> you don't exceed Vce; controlling currents will
> be trivial (<5A for all but largest VTTC).  You
> could
> could control screen grid bias on 4PR style tubes
> and drop controlling current  requirements
> another order of magnitude.
>
> I have considered breadboarding the same type
> control (Hyper-staccato???   ;^D )  Basically power
> supply could be filtered DC or an AC level shift
> power supply.  You gate oscillator on as normal
> burst controlled staccato but you terminate
> oscillator burst when cathode current exceeds some
> value, rest tube for some time (.5-2ms) then repeat.
>
> A "POP-POP-POP--rest--POP-POP-POP-rest-POP-POP-POP
> -long rest- REPEAT sort of sequence.  Each POP would
> be similar to present DRSTTC systems (50-200us
> depending on resonant frequency, and oscillator
> build up time to current limit.  Number of POPS in
> pulse train, rest times (intra POP and burst long
> rest)
> could be programmable via a PIC or FPGA style
> controller.  This control method is identical to
> present
> PIC, uP controlled DRSSTC systems, but implemented
> on a VTTC.
>
> To my knowledge, such a modulation "recipe" has
> never been attempted (at least in public domain)
> on a VTTC system.
>
> SNIP
>
> -Brett
> -----------------------
> Regards
> Dave Sharpe, TCBOR/HEAS
> Chesterfield, VA USA

Yes, since I have a remote interruptor built, as well
as an 833A system set up, I may try this myself soon.
I will be building my first DRSSTC relatively soon
(definately this year) so I will have IGBTs around.
Shortly before you wrote me about this I was
considering a simple IGBT brick driver (like Steve
Conner's circuit) connected to the SSTC interrupter.
This should produce spectacular results on a vttc
running filtered DC.

-Brett







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