Re: Terry's DRSSTC - First light ;-))

["Tesla list" <tesla@xxxxxxxxxx>]

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

Hey Terry,

Congrats on some great sparks :-)

I really like the sequence of still frames you posted of the failure,
the whole driver is nicely lit up :-).

It still seems to be somewhat of a mystery as to why primary strikes
are so catastrophic to a DRSSTC.  Some of my coils have survived many
primary strikes, other times just a hint of a streamer forming on the
primary will kill the thing.  It seems that some coils are more prone
to failure from a primary strike as well.  It might be possible that
the streamers short out primary turns making for a nice short circuit
load on the driver.  I cant see how the low primary impedance and all
those snubber caps and TVS couldnt keep voltage transients to a
minimum during such an event.  Either way, you really have to protect
all that stuff from the streamers!  I put metal caging around the base
of my coils, which seemed to work fine until i switched to primary
feedback (now the fence sucks up a lot of power for some reason).
Still a bit puzzled about that...  In any case, a well placed strike
ring as well as a breakout point that guides the sparks outward goes a
long way to keep those arcs out of there ;-).

So what primary current were you running?  What ON time and BPS?  Did
you try letting it arc to grounded targets at all?  And finally, how
long were those streamers?

Anyway, keep fine tuning that system and im sure you will end up with
something very reliable.

Seeya,

Steve


On Sat, 05 Mar 2005 23:44:21 -0700, Tesla list <tesla@xxxxxxxxxx> wrote:
> Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>
>
> Hi All,
>
> I hauled the thing over to Jerry's house tonight to run it at full power!!
>
> Works great!!
>
> Pretty pictures from handycam video (forgot to take good pics...)
>
> http://drsstc.com/~terrell/pictures/FirstFullRun-01.jpg
> http://drsstc.com/~terrell/pictures/FirstFullRun-02.jpg
> http://drsstc.com/~terrell/pictures/FirstFullRun-03.jpg
> http://drsstc.com/~terrell/pictures/FirstFullRun-04.jpg
>
> It worked perfectly until I got a primary power arc which took out two 
IGBTs:
>
> http://drsstc.com/~terrell/pictures/Frame19795.jpg
> http://drsstc.com/~terrell/pictures/Frame19796.jpg
> http://drsstc.com/~terrell/pictures/Frame19797.jpg
> http://drsstc.com/~terrell/pictures/Frame19798.jpg
> http://drsstc.com/~terrell/pictures/Frame19799.jpg
>
> Damage seems very minimal at first look.  Just two IGBTs blew their tops ;-)
>
> http://drsstc.com/~terrell/pictures/IGBTsetTwo.jpg
>
> There is a DIVX movie here (16Meg) of the last few moments.
>
> http://drsstc.com/~terrell/pictures/FirstFullRun-short.avi
>
> So it runs great!! and the two IGBT explosions, so far, are well 
explained...
>
> Replace the IGBTs and make a strike rail and off to the next road trip ;-))
>
> Cheers,
>
>        Terry
>
>