RE: Help! My Coil Blew Up

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

Original poster: "David Trimmell" <humanb-at-chaoticuniverse-dot-com> 

Sue, I hate to think you are getting the cold shoulder? I am a SSTC
cheat as of yet, only using Dan's PlasmaSonic so far. So I know you have
done much more than myself. Sometime this year I hope to try my own self
made SSTC, but time is not real free for me. One thing I have had an
interest in is details of your Plate modulated audio VTTC, can you
share?

Thanks,

  David Trimmell

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, February 04, 2004 7:48 PM
To: tesla-at-pupman-dot-com
Subject: Re: Help! My Coil Blew Up

Original poster: "S.Gaeta" <sgtporky-at-prodigy-dot-net>

I guess in spite of the age of the individuals involved, this SSTC crowd
is
just another "old boys" club.

I will get it working myself anyway. I have always gotten my projects to
work no matter what, and this will be no exception.


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, February 03, 2004 7:41 AM
Subject: Help! My Coil Blew Up


  > Original poster: "S.Gaeta" <sgtporky-at-prodigy-dot-net>
  >
  > I built Justin and Arons Quasi Self resonant coil, and it blew up
Friday
  > night.
  > Two mosfets failed. One was shorted and the other blew to bits. Even
before
  > it blew up I was only getting 8" stremers out of it with 130 volt
input,
and
  > the fets ran hot. I checked the phasing of all the driver coils and
  > everything looked right. The thing that was really disturbing was
that I
was
  > getting ringing on the output of the H bridge even with a light bulb
as a
  > load, and 12 volts pure DC on the rails. Some pics of the coil, and
  > waveforms can be seen at
http://community.webshots-dot-com/album/113763981zJBnik
  >
  > Well anyway, the two mosfets that shorted were not supposed to be on
at
the
  > same time. The two that were bad would have placed a short right
across
the
  > DC buss. The other two tested good. It appears that the driver
survived
all
  > this mayhem. It puts out a good waveform with only the good fets
connected
  > to it. So at 8:15 PM, the cause of death was determined to be shoot
  > through. Now I had 10 ohm resistors in series with each gate with the
  > schottky across each one. It did improve the waveform, so the only
thing
to
  > do now is try and improve the layout of the GDT and MOSFETs.
  >
  > I re-read the HV Guys instructions, and realised that I messed up big
time
  > with the antenna. They say to put it no closer than 20" from the
secondary,
  > and I had mine maybe 6" away, so maybe having it too close may have
  > introduced parasitics, or some other bad noise into the system. I
also
used
  > 13 turns on my GDT instead of 10 like they suggested. With my
resonant
  > frequency being around 236 KHz, which is a little on the high side, I
could
  > probably do better with less turns on the GDT. I also noticed that
they
  > don't have a toroid in their photos. I used one because Dan's SSTC
had
one,
  > but his circuit is also completely different than this one. Are
Toroids
bad
  > with this design?
  >
  > Has anyone else had problems with shoot through or cross conduction?
  >
  > If anyone can offer me any further insight, or suggestions, I would
really
  > appreciate it!
  >
  > Thanks,
  > Sue
  >
  >