Terry's DRSSTC - The Bridge...

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Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi All,

Parts are coming in for the input power section of my DRSSTC thing :-)

http://www.hot-streamer.com/TeslaCoils/MyCoils/DRSSTC/PC090025.JPG

Newark charged my card $200 for the "two" Simpson meters so I guess they 
are on their way too ;-))  The Hammond box's quality was a little low these 
days, but some news screws and a 8-32 tap fixed it...  I hope that 3/8 inch 
brass hardware does not go "poof" :o)))

I am tempted to stuff the controller and inverter in there too, but I 
"need" to keep them separate so the box can do all the fun other uses too...

So I woke up at 3:00 AM last night thinking about the "perfect" 
inverter...  Worked on it all day...  Here is my "totally untested 
resulting thought"...

http://www.hot-streamer.com/TeslaCoils/MyCoils/DRSSTC/DRSSTCdriveThought.gif

Here is the idea, left to right...

The big 4.7uF poly caps take much of the 100kHz+ resonating currents 
reducing the load on the electrolytics of the power section.  Dan does have 
this on his schematics, but I just missed it...

The 240V MOVs are added here for when things go all the heck and trying to 
save components in the case of an explosion...  They are redundant in "my" 
case, but they are "cheap" ;-))

Yes, I do "not" have gate drive transformers or any of that...  I am making 
power supplies off the line voltages available to power the IGBT 
drives...  The 20K resistor, 27V Zener, and 10uF cap (I note your all's 
love for Dan's use of these tan caps :o))) form a little power supply to 
drive the IRFBC30A FET and 1000uF cam to bias a "big" power supply for the 
IGBT drive...  Yes, I am going with higher than 15V gate drive for "sure "! 
:-))

http://hot-streamer.com/temp/OLTC08-30-02.gif

I like to drive IGBTs with heavy voltages to be sure they do not "fold" on 
us...

A massive ceramic cap to supply the TLP250 with 10 times it's specified 
instant current ;-))  These are relatively cheap parts, so the heck with 
it...  Then the fabulous TLP250 IGBT driver...  Dave turned me on to 
it.  Seems to run IGBTs well over their ratings real good :-)  Since it is 
grounded to zero volts on the low side, a gate discharge diode probably 
just hurts things here...  The TLP250 Is a 2500 Volt gallium arsinide high 
speed opto isolated thing with like 1pF of transfer capacitance...  It is 
powered by a simple "LED"...  Perfect for gate drive signal goofiness to 
follow later...  But be sure to switch those simple LEDs "fast" and no 
cross conduction ;-))

http://rocky.digikey.com/WebLib/Toshiba/Web%20Data/TLP250.pdf

The usual 30V transorb to protect the gate...

The IRG4PF50WD is a really cheap (like $6) but capable IGBT (with reverse 
diode)!!  If we can "time" things for that "zero current crossing stuff", 
it won't get too hot...  Maybe like a 1.5 kW system perfect for 120VAC 
stuff....

Important thought!!!  If we run our DRSSTC at 120 Hz,  We can take 
advantage of the AC line high peak currents and vastly reduce the size of 
the filter electrolytic caps...  Why do all that "filtering" when we can 
just run resonate with the AC line too...

The input side "variac" could easily all be "solid state" in this case too!!!

Cheers,

	Terry