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Hi, I'am testing my medium sized drsstc with steve's OCD driver and full bridge of hgtg30n60's. But it works kinda strange, i was regulating input voltage and viewing size of sparks, and on over 100VAC sparks stopped grow, OCD works fine I think, ocd led wasnt flashing, and on higher voltage an arc sometimes jumps from seconadary to primary. But coil is tuned fine. Anyone has this strange problem before?
Registered Member #1875
Joined: Sun Dec 21 2008, 06:36PM
Location:
Posts: 635
I am no expert but I think your sparks may be detuning your coil. The sparks add extra capacitance and eventually lower the Fres enough to affect tuning. Are you using primary feedback? If so, try lowering your primary resonant frequency.
I think it was EastVoltResearch who explained tuning once... If I remember correctly, he said it will break out at higher power all at once when tuned properly. It makes sense, since it will be out of tune until there is substantial streamer loading.
So try tuning slightly lower... After getting someone else's advice. :)
yea primary feedback, of course i have try to tune it, by putting bigger cap to primary, but sparks just gets smaller even at higher voltages.. and more often sparks arcs to primary from sec.
Registered Member #1875
Joined: Sun Dec 21 2008, 06:36PM
Location:
Posts: 635
I would think you need only a small change in tuning, so I would think you'd be better off with more primary inductance rather than capacitance... Or perhaps lowering the secondary with respect to the primary?
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
ScotchTapeLord wrote ...
I am no expert but I think your sparks may be detuning your coil. The sparks add extra capacitance and eventually lower the Fres enough to affect tuning. Are you using primary feedback? If so, try lowering your primary resonant frequency.
You need to tune it low so that when you crank up the power the sparks pull the coil into tune.
My MMC is 190nF in tune for small voltages, and then i added 9,5nF, sparks was shorter on small and higher voltages... so this didn't helped.. no matter i try to tune, sparks never gets bigger over 100VAC on bridge..
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Yes, it sounds like detuning. To properly tune the DRSSTC for maximum arc output, you really needed to monitor primary current vs. input voltage.
Basically, you'll want to detune your DRSSTC at low power levels. This will be evident when it takes a LOT more current at lower voltage to generate the same length sparks as if it was tuned for lower power.
So in a nutshell, your coil is really detuned initially, and it requires the capacitance of the longer streamers to bring it back into tune.
The best way to go about this is to measure primary current vs. input voltage to hit a set strike target. Move the strike target away in say small increments taking this data. Then repeat for various tuning points. Stack all the data and you'll be able to see trends on detuning /retuning, etc...
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DRSSTC problems
