Re: 4 stage SISG

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

Phil, all,

I think one good alternative to IGBT and SG driven coils
is the vacuum tube Tesla coil (VTTC). Brett Miller has been
discovering this recently as well as a few others. Although
vacuum tubes don't run quite as efficiently as solid state
devices, they are still considerably more efficient than
spark gaps. And vaccum tubes are MUCH more forgiving
of accidental short circuits and such than solid state IGBTs!
And if you run a relatively high primary circuit voltage, you can
get some pretty impressive "continous wave" spark lengths in
stacatto mode with only a single 833A type of vaccum tube.
Cameron Prince (and I soon followed his lead) was brave
enough to dare to run 2 seriesed MOTs through a voltage
doubler circuit and break the 36" spark length barrier with a
SINGLE 833A vacuum tube in stacatto mode. Cameron followed
Steve Ward's single MOT'd, voltage doubler, 833A tube driven
VTTC plans, with the John Freau stacatto controller, but instead
of the single MOT, he opted for 2 seriesed MOTs and
still used the voltage doubler circuit. Cameron also tried
raising the grid leak coil further above the primary coil
than most other VTTC coilers had been doing up until this
point, and instead of getting 22" sparks, he ended up topping
out at 37"! I have followed Cameron's lead and gotten very
similar results with my 2 seriesed MOT'd, single 833A
driven VTTC. And both Cameron and myself are using
USED 833A tubes with no idea of how much use and abuse
that the tubes had already sustained before we ever got them!
>From my experience, 833A tubes rock (and 833C's with their
graphite plates) are even tougher! And I'd imagine that other power
transmitting vacuum tubes have very similar durability as well.

I would like to eventually take the IGBT SISG plunge, too, but until
my electronics savvy and my pocket book feels a bit more "up
to the challenge", I am going to be sticking with the SG and the
vacuum tube driven variety of Tesla coils for building/operating.

David Rieben

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Monday, February 19, 2007 5:10 PM
Subject: Re: 4 stage SISG


> Original poster: FIFTYGUY@xxxxxxx
>
> In a message dated 2/18/07 9:08:49 P.M. Eastern Standard Time,
> tesla@xxxxxxxxxx writes:
>
>  >I've priced suitable IGBTs.  "Sticker shock" is an understatement.
>
>      Yeah, but Terry says they should last "forever" and have zero
> maintenance. Factor in near-silent operation, almost perfect
> efficiency, and the ability to "box up and forget about" the entire
> primary system, and I think it's definitely worth every penny.
>
>      Of course, in the past three weeks I replaced two inverter
> drives at work that decided to blow up (7.5kW where the Semikron
> brick vaporized, the other a 15kW where a cheap *input rectifier*
> exploded on power-up). Telemecanique Alitvar 31 VFD's, if anybody's
> counting. No line or load reactors in the drives, and none with the
> OEM's installation (!). Only six months old... and these are mature
> industrial power electronics from a major manufacturer.
>
>      To me, "solid state" means it's only solid until it becomes a
> conductive vapor. At least a few minutes with some emery cloth and a
> bit of fiddling is all it takes to get a SG back in working condition.
>
>          I've got 10 of the IRGPS60B120KDP's on back-order from
> Digi-Key for a month now, so I'm in the same boat as you guys. Could
> somebody please tell I-R to start making more? Or are we gonna start
> having "roll-your-own IGBT" discussions? Will gluing a glass
> microscope slide and an extra layer on an SCR do the trick? ;)
>
> -Phil LaBudde
>