Re: some new ideas for the SSTC guys

["Tesla list" <tesla-at-pupman-dot-com>]

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.

Dr. Resonance

Resonance Research Corporation
E11870 Shadylane Rd.
Baraboo   WI   53913
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <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
tap
 > >which I attached to the "normal" primary coil.  With some re-tuning it
was
 > >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
a
 > >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
a
 > few amp streamer hits would not hurt much on a conventional coil.  Even
the
 > OLTC was pretty well protected with a few transorbs.  Dan's book shows
that
 > 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 ;-)))
 >
 > Cheers,
 >
 >          Terry
 >
 >
 > >
 > >Dr. Resonance
 > >
 >
 >
 >