OLTC update

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi All,

Today I set up the coil for action:

http://hot-streamer-dot-com/temp/OLTC08-24-02.jpg

I powered up the coil at low power and brought the coil into tune by
selecting toroids and the distance they were above the coil.  I ended up
with one of Finn's toroids about 8 inches from the top of the coil.

I brought the coil up at low power.  The first notch timing was way off.
Instead of being about 102uS it was closer to only 45uS.  The ring up was
also far faster than anticipated:

http://hot-streamer-dot-com/temp/OLTC08-24-01.gif

I ran a bunch of MicroSim models and determined that the coupling was an
astounding ~0.30  Far higher than anticipated.  Apparently, single turn
primary coils (or single coils with three spread conductors like this coils
uses) are capable of very high coupling.  I tried raising the secondary but
the coupling tended to stay very high.  I could raise the coil to get it to
about 0.15 but the power of the coil obviously diminished.

Realizing that this problem would need considerable more study (and time),
I went ahead with the other testing.  I was able to lock a dwell timing on
the first notch despite the fast time.  The spike protection circuit of
yesterday was obviously working.  I was getting a small electrostatics
shock off the adjustment knob and low power but just since I was close to
the coil.  All else seemed well so I removed sensitive test equipment from
the area.

As the power increased, the machine seemed to almost shake the room.  Even
though there was no spark gap firing, the caps and coil had a profound
electrostatic sound to them.  Slowly turning up the power I go the first
arc.  However, it was primary to secondary corona.  The plastic stretch
wrap is obviously a very good insulator!  I fiddled with the tuning a bit
more and placed a piece of G-10 between the IGBT array and the secondary.

This allowed me to turn up the coil for the first small streamer action:

http://hot-streamer-dot-com/temp/OLTC08-24-03.jpg

I turned up the power more until I got streamers about twice this size at
about 5 inches.  I was just about to snap the camera when it made an "odd"
sound.  I turned it off instantly.  I found no obvious damage and the coil
repowered fine.  I think it was either corona breaking out somewhere I
didn't see, possibly a larger streamer, or a loss of control in the
electronics.  Definitely a "different" sound.  So I ran a little longer at
lower power to confirm there was no damage and shut down.

I was unable to work on it for the rest of the day.  Due to other commitments

I am going to look at the "flight recorder" video tonight and think on
things.  

So it is basically working :-))  The coupling is probably a bit of a messy
issue I need to look into.  The primary to secondary spacing may be too
small too.  The coil was happily arcing to the IGBT array and all with no
damage.  Other than the possible late problem, all the control electronics
seem to perform perfectly.  So, I really didn't get much time to work on
it, but it went pretty well.

Cheers,

	Terry