Re: Help! My Coil Blew Up

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

Original poster: "pjj" <tha3rdman-at-comcast-dot-net> 

I'm no expert, not even close but just from what I have read and correct me
if I am wrong, but . . . A larger torrid would inhibit break out and I don't
remember why but SSTC and ?VTTC? don't like that,  but that's just what I
remember reading and there-in lies 2 problems my memory, and word of mouth.

Paul

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, February 05, 2004 10:17 AM
Subject: Re: Help! My Coil Blew Up


 > Original poster: "Robert Jones" <alwynj48-at-earthlink-dot-net>
 >
 > Hi,
 >
 > I think you may need to give people a little more time to respond.
 >
 > I don't have any direct experience on SSTC.  Your failure sounds like it
 > could be caused by a lot of things.
 >
 > I would expect the bigger the toroid the better to get your frequency
down.
 > Your frequency does seems high that maybe causing the unexpected heating.
 > In any case if the fets are getting unexpectedly hot it indicates you have
a
 > problem. I think you need clamping zeners too. Stick to 12v in till you
have
 > every thing looking right unless you have a bucket of new fets.  I also
 > suggest you run it of an external oscilator untill you have it all checked
 > out and check the signal from your pick up.
 >
 > Your link down loads a file with an unknow extension??
 >
 > Bob
 >
 > ----- Original Message -----
 > From: "Tesla list" <tesla-at-pupman-dot-com>
 > To: <tesla-at-pupman-dot-com>
 > Sent: Wednesday, February 04, 2004 7:48 PM
 > 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
 >  >  >
 >  >  >
 >  >
 >  >
 >
 >
 >