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Even More DRSSTC numbers

Original poster: Steve Ward <steve.ward@xxxxxxxxx>

Hey Guys,

I built a nice little CT today using a somewhat large ferrite core
with some 200 turns or so of 30awg wire (i cant remember the exact
number), loaded down with about 2 ohms of resistance, gives a nice
100A/1V output to the scope.  I calibrated it against a nice *real* CT
(its hall effect though, and only rated to 200A or something).  Should
be "good enough" for DRSSTC use.  Anyway, i took down some numbers,
they are posted at the bottom of this page:


I haven't really analyzed the numbers so much yet.  I did look for the
peak efficiency to find the constant if we were to modify John Freau's
spark length per watt formula( SL=K*sqrt(P) ).  Looks like the best i
can do is K=1.57, vs the 1.7 figure typically seen, and thats at 70uS
burst lengths (only 20" spark though).

One interesting thing is that the peak currents dropped lower as i
increased the burst length!  I wonder if this may have something to do
with my somewhat small electrolytic (only 2900uF a piece).  The
highest peak current i monitored was 450A, it might have gone just a
bit higher during ground strikes, though.

Maybe if i get really ambitious i could plot these points to compare
the 20" tests vs the 25" tests.

At the moment I'm pondering either converting the setup to a full
bridge, or altering the tank Z to see if i can get a better efficiency
from this coil.  I believe that either halving the tank Z or doubling
the drive voltage (moving up to full-bridge) would require about 1/2
of the burst length (ON time)...  would be interesting to see if I'm
right, and furthermore to see the resulting spark length formula

Just more food for thought...

Steve Ward