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my SSTC 2nd take

raff, Wed Nov 04 2009, 06:41AM

here is a rebuild of my SSTC...

after killing a dozen mosfets, I again gathered MORE info... but mostly it was lack of know-how on the interrupter circuit having LARGE ON TIME at low BPS (1Hz 10mS perhaps //was thr single 555 interruptor ckt) and NO decoupling cap at bridge!!! I was using VCO/PLL <and maybe some hard switching> ... sigh..

the Halfbridge, the osc/gdt driver/DR interrupter

the osc circuit mostly from the miniBRUTE (thanks Dan/EVR) only lacking is the LM311 and associated electronics for current sensing..but it does have shutdown feature although not used for now..

fullwave rectified + 100uF smoothing cap... and 47uF de-coupling cap..also my gdt.. yeah its SMALL but with only 15T = 970uH.. nice find!

interruptor..still coppied from the advanced modulator but only part of it.. cap used was 39nF instead of 33nF for the BPS and PW...

CT feedback through secondary base.. 44T = 760uH .... my board also has provision for antenna feedback but I think CT feedback is better

lower left is the MMC = 50nF @ 1.5Kv primary coil is 33uH(measured)

arc from 110Vac 500w stepdown... If I draw an ARC using GND wire (at >>200uS ON time & 220BPS) I could SEE the difference between a normal SSTC and a DR-SSTC... the ARCS appear to be continuous .... though output is thin and branching.. maybe IF I "up" my ON time, maybe I will get THICKER arc... BUT IM AFRAID i will just kill the lowly IRFP450 im using in there...

I have powered this thing direct from 220Vac mains, and the output IS wow! Im afraid to draw ARCs.. LoL... its noisy also.. maybe later I will post video..estimate of arcs-to-air is about 6-7", I havent tried drawing arc to GND yet ( I know they are GREAT to) I just love the streamers, sort of an SGTC...

AND maybe will just power this up using halfwave rectified mains UNsmoothed so I dont risk killing my mosfets...

or IM NOT SURE IF I can really make this a proper DR... and I cant get IGBT either ..and lack of resources to order one...

Im not really sure what to DOafter this.. maybe I will just be happy with it being an SSTC...

but I do need your inputs!

Re: my SSTC 2nd take
Robert2, Wed Nov 04 2009, 09:19AM

Change CT for 1:70 and GDT for bester ferrite core and use 1:2:2

Re: my SSTC 2nd take
raff, Wed Nov 04 2009, 10:49AM

Hi Robert2

I may improve my GDT turns If I manage to get a bigger diameter torroid core(otherwise its working beautifully)... for the GDT, 15T = 970uH is a good ferrite material... im driving my gdt driver chips (UCCxxxx) at 15V so no need to go 1:2:2 unless someone can donate IGBTs as christmas gifts... LoL

the arcs "look" small because Im using an interruptor FOR A DR(w/c btw has very narrow ON time) .... I have tested it with my other interrupter(using single 555//classic sstc int) and THEY DO create THICKER arcs...though I had to use halfwave rectified unsmoothed supply...

one more thing to experiment for now, need to get better coupling of the primary...

oh and BTW,
my main concern with THIS THREAD was:
will it be OK to turn this into a DR ( a low powered one is FINE by me ) with the use of AT LEAST IRFP450?? though I could get IRFP460(but not cheaper)

or just forget it and be happy with an SSTC?

EDIT:
SEC_Freso btw is around 210KHz with topload(1.35" x 9") though I could go lower by adding more smaller torroid topload...

Re: my SSTC 2nd take
raff, Mon Nov 09 2009, 02:20AM

ok here is my FINALIZED setup..

made better wiring and placed de-coupling cap(hadnt had one before in my previous setups = blowing FETs)

using antenna feedback now(CT was kinda worse in my setup with using LESSER turns and tighter coupling of pri-sec)..

a *better* video of this... arcs of 6-7" to free air.. (im using IRFP450 so I dont expect much)

Re: my SSTC 2nd take
brtaman, Mon Nov 09 2009, 01:03PM

Nice work, raff! The board looks great.

What are your future plans for the coil, I see you made the MMC, I assume DR is the future for the coil?

Best Regards,
brtaman

Re: my SSTC 2nd take
Killa-X, Mon Nov 09 2009, 10:15PM

Sorry to bust a question into a thread but..A CT is supose to have only 1 coil on the tesla connections? I miss heard then! i did my tesla coil to 30 turns, then to ground. and 1 turn for the antenna of the UCC..Whoops?

Re: my SSTC 2nd take
brtaman, Mon Nov 09 2009, 10:28PM

Killa-X wrote ...

Sorry to bust a question into a thread but..A CT is supose to have only 1 coil on the tesla connections? I miss heard then! i did my tesla coil to 30 turns, then to ground. and 1 turn for the antenna of the UCC..Whoops?

Yeah, big whoops.

Opposite is the way to go.

Re: my SSTC 2nd take
raff, Mon Nov 09 2009, 11:19PM

brtaman wrote ...

Nice work, raff! The board looks great.

What are your future plans for the coil, I see you made the MMC, I assume DR is the future for the coil?

Best Regards,
brtaman

Hi Rok,

I have made FEWER turns on the primary (now its 7 only, it was 13 before) now I could get 10"-11" arcs to free air.. NOW I have exceeded the secondary coil length (10") YAY!:-D

I forgot to mention, my supply is 220Vac -> halfwave rectified mains UNfiltered..

later this afternoon (about 5PM) I will take a vid of it...

yeah, DR is on the way.. though I have to re-calculate my primary LC tank... primary L=10uH and the secondary(and topload) unloaded Freso = 178KHz ... any idea how LOW the Freso will be when it is doing breakouts?

Re: my SSTC 2nd take
raff, Wed Nov 11 2009, 07:45AM

OOPPSSSsss!!

I thought I already had posted my latest update.. here goes..

Im back to using CT again... and primary is down to 5 turns..

videos: 15fps only..

taken late in the afternoon

ok enough for a IRFP450?

Re: my SSTC 2nd take
raff, Sun Nov 15 2009, 02:32AM

just posting arcs :) varying ON time and BPS...