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Re: some new ideas for the SSTC guys
Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com>
Larger coil diameters and a flat spiral was my "other" idea as well. I
think the series fed sec might be the way to go to prevent IGBT explosions.
Resonance Research Corporation
E11870 Shadylane Rd.
Baraboo WI 53913
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
Sent: Monday, October 04, 2004 8:26 PM
Subject: Re: some new ideas for the SSTC guys
> Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>
> Hi DC,
> At 08:58 PM 10/3/2004, you wrote:
> >Problem --- Exploding IGBTs when they are hit with a sec - pri spark
> >(Terry Blake's coil terrible demise at our Teslathon).
> >A few years ago I did some experiments with a flat spiral coil (18 dia.
> >sec.). In the classic configuration with a .05 uF cap, RSG, and 4.5 turn
> >primary the sec sprayed out 8 ft long sparks.
> >At the urging of a plasma physics guru from UW-Madison (Paul Nonn for
> >those of you who might remember meeting him at Ed's recent Teslathon), I
> >removed the sec coil and placed it on a stand 10 feet away. I used a 7
> >inch corona ball on the bottom to prevent any corona and used a single
> >which I attached to the "normal" primary coil. With some re-tuning it
> >again spraying out 8 ft sparks.
> High coupling is not required if the primary and such losses are low. If
> there are nil losses, there is only one place for the power to go
> ;-)) Even 0.03 CCs work in many cases!!
> >What I'm getting at here, is, the SSTC experimenters, Dan M., Steve W.,
> >etc, might try using a larger dia sec coil and then use a 15-20 turn test
> >primary coil while feeding the sec coil a few feet away. If this works,
> >then the greatest danger to SSTCing, ie, blowing the IGBTs should become
> >problem of the past.
> My failed model was also trying to reduce coupling to "isolate the primary
> circuits from bad secondary effects. Modeling always tended to show that
> few amp streamer hits would not hurt much on a conventional coil. Even
> OLTC was pretty well protected with a few transorbs. Dan's book shows
> a ground strike can greatly increase IGBT current which certainly is a
> factor to be dealt with!!
> >It will take some experimenting --- perhaps the best tap is "inside" the
> >normal classic tap location or perhaps it will be "outside", but either
> >way, getting the sec away from the primary to act as a series fed setup
> >should eliminate the IGBT explosion problem. If it does work the primary
> >can be either a flat spiral or normal solenoid coil --- perhaps enclosed
> >in clear acrylic with a large "feeder" wire over to the sec coil.
> I think they should reduce the coupling a bit and go with a flat
> spiral. But what do "I" know :o))
> >If someone DRSSTC tinkering wants to experiment with this idea on their
> >present or planned near future coil, please advise and I will send you a
> >nice 10 ft long chunk of #6 AWG for experiments --- with 125 kV BIL
> >insulation --- it's 1 inch thick and offers great HV feedwire
> >performance. We use this "big Red" on all our HV power supplies to feed
> >the 14.4 kV HV over to the base of the oscillator.
> >Might work, might not, but worth trying.
> Ya always have to keep trying ;-)))
> >Dr. Resonance