OL-DRSSTC 8 - Triggers and RUNs at 60 BPS now!!!

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi All,

The OL-DRSSTC (I am open to suggestions for a better name :o))) "runs" now!

I finally found the problem with the trigger circuit.  The trigger 
was turning on the IGBTs for 5uS just like it was supposed 
to.  However, the primary capacitor was charging up to the bus 
voltage every time it did that.  So the H-bridge was pumping 200 
volts across the primary cap, but the primary cap was already charged 
to 200V!!  Thus, no current flow....

The solution was trivial.  I just added two 47k 1/2w resistors 
between the H-bridge output and the buss to charge the thing fully 
negative on the dead cycle:

http://hot-streamer.com/temp/OL-DRSSTC-07.gif

So the bias resistors charge the primary cap to about -200V and then 
the IGBTs pulse on at +200V!  NOW we have current :-))))

I did not have time tonight to get any pretty pictures or 
anything.  I am not setup to run the coil at full power at this point 
either...  But most of the technical details are fixed and I took 
away all the test equipment since it works now.  So, all is going 
extremely well!!!

Cheers,

	Terry