Re: some new ideas for the SSTC guys

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

Original poster: "John" <fireba8104-at-yahoo-dot-com> 

Terry,
Your driving me nuts. I was going to test out a small cap and flat primary 
on my mini DRSSTC!!! I thought about using a smaller cap after looking at a 
thread on 4hv-dot-org. In this thread, one member stated the common rule of 
doubling capacitance only increases energy by 2 fold while doubling voltage 
increases energy by 4 fold. I figured since a Drsstc rings up, a higher 
reactance cap will ring to a higher voltage and thus a higher energy than 
that of a system using a capacitance twice as big.
The flat primary was only chosen since it would not have as many insulation 
problems as a helical. Also I think it looks alot better. :-). Next time 
I'll open my mouth earlier, till than my hat is off to you my good chap.
Cheers,
John

Tesla list <tesla-at-pupman-dot-com> wrote:
Original poster: Terry Fritz

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
 >