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DRSSTC frustration

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Zum Beispiel

Mon Sept 24 2007, 11:22AM

Registered Member #514 Joined: Sun Feb 11 2007, 12:27AM
Location: Somewhere in Pirkanmaa, Finland
Posts: 295

This has been said already, but what the heck:

Don't worry. These things take time. Believe me, I know how frustrating it is when something doesn't work (Especially when you know it should work, but doesn't).

The same thing about blown parts: When you build something that you have no previous experience from, you are bound to destroy some silicon. I've saved every one of those anti-static bags that the parts are packed in. And when I compare the amount of those bags to the amount of working stuff I've build, I wan't to cry. With the money I've spent on parts that I blew up, I could have probably gotten myself that Tektronix TDS2014B that I've been wanting, or something else fun.

My bigger SSTC blew up 5 times before I got it working reliably. And as you know a DRSSTC is about 100 times more complex than a "stupid normal SSTC".

Don't give up. You're a smart guy, you'll get it working eventually.

uzzors2k

Mon Sept 24 2007, 02:28PM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

You have the wrong perspective on it Marko, it's not wasted time or money if you've gained experience. Which you have. All the "solid state junk" is good learning and teaches electrical principals, hell, I learnt a lot just following your threads. Every hour and semiconductor "wasted" is the price of experience and learning. Eventually you'll become so 1337 that you stop having failures, and only then do you stop learning.

101111

Mon Sept 24 2007, 03:23PM

Registered Member #575 Joined: Sun Mar 11 2007, 04:00AM
Location: Norway
Posts: 263

Now i am feeling lucky, i found my 20mhz oscope and got it calibrated for free.

I have done so much testing and failing 98% of every thing i build don't work.

colin heath

Mon Sept 24 2007, 07:00PM

Registered Member #123 Joined: Fri Feb 10 2006, 12:58PM
Location:
Posts: 162

Hey you haven't seen a frustrated bloke till you seen me at a teslathon trying to run a ssstc drsstc or anything else with silicone. Not one has worked until i get it home,cool down and take a fresh look.

Cheers

Colin

Marko

Fri Sept 28 2007, 06:46PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Guys, thanks a lot. First post is apparently pointless, but I just felt so much easier after confessing my sins.
I focussed back on work.

The dimmer has died, went completely short.
I added another 3 primary turns, and scoped it while tuning. Tuning up or down for like 2 turns makes very little difference.

Using a 50V supply I get around 200amps of current, if my current transformer is fine what I don't know, although OCD tripping is consistent with that. Tuning much lower current stays about the same, but output diminishes.
I don't get much of current or output rise after 100us so I limited it there.

Now, spark output is still completely poor no matter what I do. With 200A I get like 3-4cm streamers. I feel that for any significant spark length I'm have to hit enormous currents like 800amps which is far beyond capabilities of my IGBT's and caps.

Everyone shouted ''use low characteristic impedance'', and I'm afraid I got it too low now.

My coupling may also be too low, I don't know.

If caps are good, I don't know what else could be going wrong.

I'm using water pipe for ground, and since then, it seems that arcing on my bridge has stopped. Interestingly it makes no difference when I connect it to mains ground, so I'l leave it on pipe for now.

I'l get around posting some pics.

Marko

vasil

Fri Sept 28 2007, 07:16PM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

Is it your GDT/ driver output/ primary phased corectly together? I mean you get oscillations even it is not correct phased but the streamers dont grow. Did you try to reverse the primary connections? I observed that in drsstc work the winding direction of the secondary regarding the winding direction in the primary coil is important.

Danielle

Fri Sept 28 2007, 08:10PM

Registered Member #632 Joined: Mon Apr 09 2007, 01:09AM
Location:
Posts: 267

I have had the same problem you have right now so I am constructing a new driver that will hopfully work under all conditions and faults and report what they are. I am also building a new much more rugged brige because 72" wasnt enough. If you find what is wrong I think it will help me too. Just to tell you what I found so you might not have to truble shoot in the dark is all the diodes and UCCs were good and the signal from the inturupter was being fed to the CT but no osscilation was occuring because it appered that only 1 IGBT was switching. If you have these same sighnes please tell me what you see as the gate signal. All my components are good and I caint find the faluar.

also I did see that the whay you connect the signal from the UCC output to the brige matters too not only the phasing from bridge to bridge.

Marko

Fri Sept 28 2007, 08:26PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

OK, what was I doing entire last year if I couldn't find the phasing?

I'l take pics tomorrow so you see what I'm at.

BTW, for those who don't know, project thread is here

Tom540

Fri Sept 28 2007, 08:49PM

Banned on 3/17/2009.
Registered Member #487 Joined: Sun Jul 09 2006, 01:22AM
Location:
Posts: 617

Hmm to me it sounds like it could be a few things. My coils don't have OCD so I run into trouble when I do certain things but I think they can apply to any DRSSTC which are:

1. my MMC has too much capacitance. 2. the coupling is too low. or 3. My topload is too large and bogging down the bridge. In those cases I get too much current draw. not enough sparkage and blown IGBT's and of course frustration. Oh yeah and the phasing thing. I don't know if this helps you but it seems like everytime i had the same problems you you did this is why. Also, I'm a snap cap user myself.

Marko

Sat Sept 29 2007, 07:15PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I tapped the primary a turn lower, and coil pumped. I was running at 50V from a small 80VA transformer, and it gave a nice 10cm streamer and 25cm sparks. And with only about 150us of on time! That was by far best 50V performance ever.

Bad news is, my dimmer is deceased and I can't be bothered to fix it.
This is a situation where it's most frustrating not to have a variac.

I'll have to find a way to regulate the input voltage into coil. I don't know, should I bother to remake some kind of dimmer, or just find a bunch of light bulbs and paralell them by required power? Or something similar?

I can't risk to give full 325V to coil and blow it up. If I slowly increase the voltage I'l at least have some chance to photograph the coil before it dies and show me to someone as a proof that I have a decently working coil.

I used a Mercury lamp ballast choke to charge to about 100V and did some single-bangs. Nice one-foot streamers, but didn't measure spark length. It should be somewhere around 30-40cm. Best ever performance for this iteration of coil.

OCD tripped during these shots so coil could have done even more.

Now it's all about if it does or does not blow up.

First pic is a tune running slightly lower than resonant frequency, current rises almost linearily and settles softly down after turned off. Poor spark output. Current is 500A div.

1191093311 89 FT31806 Lower Than Resonant

This is at best tune. Current inevitably heterodynes, but still doesn't go over 200A and sparks look good for 50V in!

This is ZCS measure. Shown is gate voltage so add IGBT delays, but otherwise looks good.

This is the produced spark:

I tried to photograph a short burst (charged bus cap to 100V) but couldn't do much with 320 iso. How do you guys photograph bursts and single bangs?
The largest visible streamer there is about 30cm.

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