[Prev][Next][Index][Thread]

Solid State Record

Thanks to all who replied to my question about records. No one had any
specific data about a longer spark from a solid state drive, which I assume
would allow me to claim the record of 57 inches to a ground rod.  Marco is
making sparks close to that length, and I expect him to exceed it when he
gets his big coil in tune.

Record claiming may be a bit like the Olympics, with categories like
tiddlywinks, arm wresting, etc.  I blame part of this trend on Terry, who
claims the record for spark length from ignition coils!  But I consider this
a part of the fun of coiling, as long as no one takes it too seriously.

In response to some of the questions:  The coil is 39.6 cm in diameter,
winding length 116.6 cm, 387 turns space wound of 14 ga wire.  Resonant
frequency is 160 kHz.  I am direct driving the base of the coil from a half
bridge of IGBTs, no primary, no high frequency transformer.  The base sees a
square wave of plus and minus 1200 V.  The Q is about 500, so by standard
lumped analysis, if the toroid did not break out, the top voltage would
reach 500(1200) = 600,000 V.  It reaches breakout voltage of about 500,000 V
about 1 ms after the pulse train is applied.  Just before breakout, the
current is in the vicinity of 30 A, so the peak power applied is slightly
over 30 kW. The power drops to perhaps 3 to 5 kW for the remainder of the
burst.  I was using 10 ms total for each bang.

At breakout, the frequency drops to about 152 kHz (due to the larger
effective toroid).  By the end of the 10 ms burst, it is back close to 159
kHz.  I might mention that the controller is a non-trivial item.  It needs
to find the exact resonant frequency, hold frequency stable at that value to
within 50 Hz (out of 160,000 Hz) before breakout, and then slew at say 100
Hz per microsecond to keep up with the changing frequency.

To my eye, the sparks look just like the sparks from a well tuned NST spark
gap coil. They are white, thick, branched, and energetic.

I don't have a web site.  I also do not intend to keep any secrets from
anyone interested in solid state drives.  I am writing up my notes now, and
will make them available for the cost of photocopying and postage.  I will
announce them on this list when I am finished.  It may be a few months.

Gary Johnson