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Re: [TCML] BIG solid state
Did I was rude? Sorry Phil. It was not intended. I include myself in the gapper category as I have limited electronic knowledge, so the phrase was directed to me more than to the others.
Do not be offended. It is not related with the age too.
vasil
>
>
>An excellent build and infinitely more complex than a lot of us could
>manage.
>A YouTube video to see the 'type' of streamer it produces would be great. >I
>say 'type' as I like the lazy wandering sort as produced by the Biggg one,
>rather than the more frantic output of some SS types.
>There are many I am sure who want to know about the fire Dept. issues, >which
>were briefly mentioned as a teaser.
>PS: I can't say I agree with Vasil's rather cheeky comment of >> " and
>they win compared with "those old spark gappers"
>Regards
>Phil Tuck (an old spark gapper)
>www.hvtesla.com
>
>
--- On Wed, 6/15/11, Steve Ward <steve.ward@xxxxxxxxx> wrote:
> From: Steve Ward <steve.ward@xxxxxxxxx>
> Subject: [TCML] BIG solid state
> To: "Tesla list" <tesla@xxxxxxxxxx>
> Date: Wednesday, June 15, 2011, 6:35 AM
> Hi Everyone,
>
> Just a post about a recent project of mine. Many
> hands involved on this one
> (see credits later). So far its just a prototype, but
> results are
> promising:
>
> http://www.flickr.com/photos/kickermagnet/5811280440/in/photostream
>
> This is, as far as im aware, the largest Double Resonant
> Solid State Tesla
> Coil built and working as intended. The machine
> stands 15 foot tall (to the
> top of the toroid). With breakout point at 16 foot
> above the ground, its
> made some 25 foot sparks. Power input at 200bps was
> measured at 33kVA
> (480VAC 3 phase, about 40.5A RMS). I estimate a power
> factor of .92 given
> the line reactor used to smooth the current peaks charging
> the 2kJ of DC bus
> storage. The secondary is 24" diameter and wound to
> just over 8 feet
> length. The toroid is 96" by 16", and is indeed very
> ugly.
>
> For now, i dont have many photos of the detailed
> construction (this is
> something i should get to soon) but you can sorta see whats
> going on here:
>
> http://www.flickr.com/photos/kickermagnet/5487415037/in/photostream
>
> <http://www.flickr.com/photos/kickermagnet/5487415037/in/photostream>On
> the
> lower level, you can see banks of white electrolytic DC
> capacitors, 3300uF
> 400V X 16 total, wired in series parallel banks, one per
> each of the 4 IGBT
> inverters. The inverters consist of a full-bridge of
> CM300DY-24H
> transistors. So each pair of half-bridge bricks
> (there are 8 total, 4
> H-bridges) drives its own .625uF 20kVAC capacitor, and
> 2-turn primary coil.
> There are 4 MMCs and 4 primaries. The mutual
> inductance between primaries
> and equal MMCs force current balancing of the 4 drives
> (each drive sees the
> same load impedance). This was chosen to avoid some
> possible issues with
> directly paralleling modules, such as, what happens if 1
> device fails? Does
> it take out all the rest? In this scheme, there is DC
> isolation between
> inverter outputs, so one inverter failure should not take
> out the other 3.
> And, in fact, if i did lose an inverter, i should be able
> to short its tank
> circuit (using its energy storage of the MMC to maintain
> tuning) and
> continue operating at 3/4 power. Hopefully it never
> comes to this!
>
> The coil has a natural resonance of about 45khz, but i
> found that de-tuning
> the drive down to 40khz or so was best to keep it in tune
> with large
> streamer loading. The primary current peaks at 6000A
> after about 6 cycles
> of excitement. The coupling coefficient of the system
> is fairly high, at
> about .19 (estimated by a 5 cycle beat period that didnt
> quite notch). So
> detuning the primary seemed to work well at efficiently
> transferring energy
> to the secondary in the event of being detuned by
> streamers.
>
> The primary copper is 3/8" diameter to keep the surface
> area down (which
> happens to reduce AC losses as the eddy currents are
> lessened). I pump tap
> water through the primary to keep it cool, as the RMS
> current is something
> like 80-100A per primary coil! Me (tall guy) and
> friend Mike working on the
> primary coils:
>
> http://www.flickr.com/photos/kickermagnet/5487414563/in/photostream
>
> The MMC is made out of giant polypropylene snubber
> capacitors, rated 5uF,
> 2500VAC pk, 3600Apk and 80A RMS each. They make the
> CDE MMC caps look very
> small indeed. I think the whole MMC bank (32 of these
> caps) weighs
> something like 150lbs. Total bank is 4 strings of 8
> in series, 2.5uF 20kVAC
> effectively.
>
> RF grounding was primarily a 4x20 foot sheet of metal
> "cloth" (1/2" square
> steel mesh) laid on the parking lot, and also clipped to
> the building ground
> rod (about 40 feet away). Would have preferred an
> even larger sheet of
> metal down there, but this was available and quick, and
> seemed to do the
> trick!
>
> Spark performance ended up being right on target, at 25
> feet, with
> extrapolations from smaller DRSSTCs (that make 10-12 foot
> sparks).
>
> I gotta thank the help of many friends, Jeff Larson for his
> use of materials
> and labor on the secondary coil for this beast. Big
> thanks to the guys in
> Arcattack, who stayed at my house for a week this january
> to help me crank
> out this prototype (we actually got it running by the end
> of a week!).
> Terry Blake has been supportive in helping setup and
> teardown of this
> system, which isnt trivial, and for being the guy in the
> suit. And recently
> Jimmy Hynes (who got me working with DRSSTCs originally)
> who visited and
> instigated the testing of this machine, and helped tune it
> up to almost
> perfectly match our expected outputs. And Dave (who isnt on
> the TCML) for
> being such an awesome host, letting us run and store this
> machine at your
> shop, and dealing with the city and fire department on
> issues that really
> dont concern them, thats a story for another time.
>
> Steve
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>
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