SISG Testing

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Original poster: "Mark Dunn" <mdunn@xxxxxxxxxxxx>


All:

I assembled (4) SISG boards and tested them on a very small coil driven
by a flyback based power supply.  Worked fine though I have not yet
re-tuned and duplicated spark length.  Tried it with from (4) to (16)
Sidac circuits(1 to 4 boards - 3600 VDC to 14400 VDC).  Could clearly
hear the bps frequency increasing as reduced the # of SISG circuits.  At
17 SISG circuits the capacitor charged up, but the Sidacs never fired -
the SISG threshold voltage was higher than the power supply voltage.

Then moved to my DC resonant MOT based coil.  Here is the schematic of
this system:

http://www.teslaboys.com/SISG/TeslaCoilv1.bmp

The MOT transformers produce about 6000 VAC which when rectified gives
8500 VDC at the filter caps.  The DC resonant circuit then pushes things
up to about 17000 Volts.

I replaced the RSG with the SISG - trivial concept, but here is a
schematic:

http://www.teslaboys.com/SISG/TeslaCoilSiSGv1.bmp

When operated the SISG fires one bang and then stays on due to the DC
current supplied by the filter caps thru the charging reactor.  The
filter caps have reduced the DC ripple to around 1000 vdc and this is
not enough to allow the sidacs to shutdown.  What I need is a pulsed DC
or unfiltered DC to make it work.

My filter caps were integral with the rectifiers on a board so I cobbled
together a rectifier and tried this:

http://www.teslaboys.com/SISG/TeslaCoilSiSGv2.bmp

I could not get this to fire.  At the time I believed it was because my
voltage was now too low, but in hindsight I think I may have blown a
rectifier.

So I cobbled up a voltage doubler arrangement like this:

http://www.teslaboys.com/SISG/TeslaCoilSiSGv3.bmp

To get my peak voltage back and have a pulsed DC charging system... But
after it did not fire I discoverd the 15 kv rectifiers were dead short.
They were the same rectifiers from the previous test so I am not sure
when they blew.

Now I planning to set up the last arrangement properly with correct
components, but am confused as to what value to chooses for the caps(Cd)
to get voltage doubling, but not smooth the DC so much that the Sidacs
won't turn off.

I am also starting to feel uncomfortable with the center tapped MOT's
tied to the voltage doubler and am getting confused as to what the DC+
and DC- legs will be out of the voltage doubler.  Comments please?  I
don't see a current path for the DC side with this set-up.

Assume the input legs to the doubler are rms 3000 VAC phase-to-ground
and 6000 VAC phase-to-phase.  Thus 4200 V peak-to-ground and 8400 V
peak-to-peak.

So I originally thought the output from the doubler would be 8400 DC+
and 8400 DC-, but now I am having reservations.  Normally, the DC- side
would be grounded, but I can't do that because I am feeding from a
center tapped MOT series(center tapped to minimize stress on the
windings).
Thanks.

Mark