OLTC update

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

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

Hi All,

Although I have been a bit lazy lately ;-)  I still am working on the OLTC
quite hard.  Much of the work right now is very time consuming trying
models and stuff.  Pretty boring especially when the results are not
significant...  Also been playing with streamer currents and such.  Also
fixing blown fiber probes as a result ;-))

I decided not to pursue the cascade Marx configuration right now.  Seems
just to complex and Ken points out some problems that would be messy to
fix.  That configuration is very interesting indeed!  But too far different
from what I have now.  It would need a multi turn primary and the caps
would probably have to be charged through very large inductors or
transistors.  Primary losses may also be a problem since fewer IGBTs and
four in series now...

I am also holding off on the OLTC-2 effort until I can find out more about
streamer loads.  Even though the losses are high right now, The early
streamer data seems to suggest that it is not that terrible of a problem.
So I am going to learn more before changing the configuration much.  I
don't want to do a be redesign and find out I didn't accomplish much.  I
was considering rewinding the secondary on a plastic form but the data say
to wait for now till I really know what the benefits will be... 

The thing I am really excited about right now is I think I found a way to
get rid of the iron core split 150mH inductor and increase power!!  By
changing the inductor to an air core 34mH coil, I can run at 240BPS.
Nothing else changes but the inductor.  The control circuit will
automatically lock on at 240Hz and run just fine.  I need to use #20 wire
to keep the resistance down but since I only need 34mH that is not a great
problem now.  Many thanks to Richie Burnett for clueing me on to this!!
This also eliminates saturation problems and gives very "nice" inductance
properties.

The schematic is at:

http://hot-streamer-dot-com/temp/OLTC09-20-01.gif

The charging waveform looks like it did before but now I have an extra
smaller bang between them:

http://hot-streamer-dot-com/temp/OLTC09-20-02.gif 

The current is nicely balanced still:

http://hot-streamer-dot-com/temp/OLTC09-20-03.gif

The line current gets strange now but it won't hurt anything.  So hopefully
I will get more power, 10 pounds lighter, and simpler (no split inductor
just a coil of wire now).  All for free basically ;-))

So I'll order up a 1000 feet of #18 wire (and a few miles of #26 in case I
redo the secondary)and get it going at 240 BPS.

I am interested if anyone has any tips on how to wind a 34mH air core
inductor with #20 wire using the least amount of wire (least resistance).
I figure a very short large diameter coil?

Cheers,

	Terry