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Re: DRSSTC eye candy (sparks)

Original poster: "K. C. Herrick" <kchdlh@xxxxxxx>

Steve (& all)-

Very nice, indeed; love those sparks! I hope your work will help restore some of my motivation; I haven't had a running coil for a year or so, now.

A few questions:

1. I take it the "1:100" c.t. is 2, 1:33 in tandem, as you mentioned elsewhere--right?

2. What IGBTs do you use--and would they work adequately @ 100-130 KHz? (My 2 secondarys are 100 & 130 or so KHz. & I wouldn't have the energy to make a new one.)

3. Why the disparity of 55 vs. 75 KHz, primary & secondary? Expediency? 55 KHz to suit the IGBTs?

4. Could you amplify on the circuits of your drawing DRSSTC Controller dated 12/18/04? I'm troubled that the J-K FF's /CLR is asynchronous with its CLK. Also, the J-K's /Q output goes high at /CLR=true, and so would seem to enable the drivers at that time. I'm confused. How do you manage to synchronize the gating with the primary current's z.c?

Ken Herrick
Oakland, CA

Tesla list wrote:
Original poster: Steve Ward <mailto:steve.ward@xxxxxxxxx><steve.ward@xxxxxxxxx>

Hey guys,

It was in the low 50's (temp) today  so i cleaned up the garage a bit
and brought my DRSSTC out there for a run.  I was happy to see it
pegging 5' and reaching out to 6' whenever it wasnt arcing to
something closer.  You can see the pictures at the BOTTOM of this


Just a few notes about this run. I did blow the 15A fuse twice (the fuse was all that failed). I think this might be partially due to my VERY large filtering capacitors (22000uF each, 200V). The 7.5A variac wasnt even warm after a long run, so im a bit skeptical if im really using 15A rms. The peak primary current surged to about 700A during stressful "short" arc conditions (like to the strike rail at about 2 feet). The longer sparks (most of the connected streamers are at 5' length or better) did not trip the OCD. The sparks out to the wall on the left were measured to 67", and i had a few reach out past 6' (didnt get any on camera though). I will have to bring the coil outside to see what it can really do... i never reached full input voltage. I was running the coil at 120bps and about 150uS on period for about 8.5 cycles. I found that increasing from 120uS to 150uS made a considerable improvement. I even had it cranked up near 180uS at one point where i was getting 5' sparks at maybe 65% input voltage! Pretty much out of room in this garage though, so i will have to wait till it gets dark and run it out in the back yard and see where this guy tops off for spark length, my guess is about 80" will be the very max.

Comments and questions are welcome.

Steve Ward