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Interesting disappearing problem with my Sstc

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brandon3055

Thu Jun 07 2012, 08:49AM

Registered Member #4548 Joined: Mon Apr 23 2012, 03:52AM
Location: tasmania
Posts: 271

Yes and yes I migh
Edit: OOPS!

brandon3055

Thu Jun 07 2012, 08:57AM

Registered Member #4548 Joined: Mon Apr 23 2012, 03:52AM
Location: tasmania
Posts: 271

Yes and yes I mightn't have had the scope adjusted right anyway I just tested it and it seems to work a bit better then before but time will tell if the mosfets stop dyeing the test was dun with those two zeners still disconnected I am currently in the process of uploading a video to YouTube but my internet is a bit slow so it will take a while I'm also thinking of increasing the primery current should I do these by increasing the capacitants or decreasing the primary turns?

Sigurthr

Thu Jun 07 2012, 10:19AM

Registered Member #4463 Joined: Wed Apr 18 2012, 08:08AM
Location: MI's Upper Peninsula
Posts: 597

Assuming those were gate protection zeners, they're only there in case the gate drive waveforms exceed the maximum rated Vgs of the fets to prevent blowing the gates. They aren't technically needed at all in a well designed and constructed GDT when using well designed and constructed gate drive circuitry and regulated supply rails. Good to have anyway, but not a necessity unless other issues are present. I'd still test and fix/replace them if I were you.

As for increasing the primary current, what capacitors are you referring to? This is a SSTC not a DRSSTC right? If so, the only capacitors would be filter/energy storage caps on the supply rails. As long as your gate drive circuitry isn't loading down the 12v rail to the point that it is dropping below 10v (unlikely! but possible if you didn't use electrolytics after the 7812 as usually recommended) there is no need to add capacitance here. If you meant on your HV/Line Voltage side, you should have sufficiently large filter capacitors that ripple is reduced enough to approximate DC, but it isn't entirely necessary either, it just improves performance to have low ripple. There should be plenty of juice coming out of the wall for such a small coil.

So, yes you would reduce the number of turns on the primary, as this lowers the inductance/impedance and allows for more current draw. If you do this keep watch of the IIR losses (mosfet temperature will rise a lot!) in all of the bridge including fast diodes and also keep an eye on primary wire temperature, you don't want to deform your resonator!

brandon3055

Thu Jun 07 2012, 10:47AM

Registered Member #4548 Joined: Mon Apr 23 2012, 03:52AM
Location: tasmania
Posts: 271

I was referring to the dc blocking caps I used the same setup as richys (posted below) 4 220nf any way I just added a nother one and a bigger top load and !CHECK IT OUT! last time I tried that I blew my entire bridge (now I know why) thanks for the help guys
BTW I cancelled the video upload it was nothing compared to this

1339066043 4548 FT139528 1258227415 2467 Ft0 Sstc02

That's 40cm and that light in the background is not termed on
BTW dos anyone know how I can protect my phone from the rf interference it makes my f phone go nuts and its a verry expensive phone $B-)$

Neet Studio

Thu Jun 07 2012, 10:49AM

Registered Member #4037 Joined: Fri Jul 29 2011, 03:13PM
Location:
Posts: 86

You don't need to use foil around twisted pairs. The twisting is to improve the magnetic coupling between the wires (gate drive and its return path) which reduce their parasitic inductance. This also lower the amount of area enclosed by the wires which help to reduce magnetic noise pickup.

IMHO foils are over rated (aka useless) for anything that is not high impedance. There is enough gate capacitances that noise pickup by capacitive coupling (not even measurable for the air gap) is not going to do anything. As for AC magnetic shielding, they are not thick enough (see skin depth) for the frequency of your SSTC to significantly attenuate.

brandon3055

Thu Jun 07 2012, 11:00AM

Registered Member #4548 Joined: Mon Apr 23 2012, 03:52AM
Location: tasmania
Posts: 271

Thanks Neet studio I will keep that in mind next time but I cant be bothered taking it bake off now and it shouldn't hurt performance right?

Edit: I just added an extra toploade (chicken wire) and now its outing out even bigger arks and the ground strikes are longer and beiffier than the arks from my dull MOT stack and everything is staying fairly cool except the secondary I might have to re concider my method for terminating the ends

the secondary is approximatly 620 turns of about .3 to .4 mm from a tv (the large coil wrapped in tape

Edit: Neet studio i have been planning on byeing sume shielded cable to connect the intrruptor do you think that's just as useless?

Edit: about the zeners I accidentally bought 100 15v 1/2w (it though they were 1w) can I run them in parallel?

Another edit can someone just reply already

I just had a question about the secondary its current res frez is around 400kHz (around 300 with the extra toploade) I've been playing to build a new secondary with a res of around 200kHz would that drop in frequency improve my gate drive?

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