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Odin The All-Fragger: a large DRSSTC

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Thomas W

Tue Jul 15 2014, 06:38AM

Registered Member #3324 Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276

Steve Conner wrote ...

The PLL driver board's own output is bipolar for driving GDTs. If you want a waveform to pass through a transformer, it has to be symmetrical (to be pedantic, the positive and negative areas must be equal) so when using a GDT the positive and negative gate voltages must also be equal.

The outboard drivers use a small GDT followed by a MOSFET stage, so they don't have this limitation. The MOSFET stage turns +12V input into +24V output, and 0 and -12 go to -12V output.

Aaah okey. Im actually using a modified version of your driver for my x-ray transformer driver, it will also be able to be used for teslacoils.
the difference is im using a single transformer for the powersupply, 4 ouputs of -12v - 0v - +24v from a home built SMPS as a half-bridge from mains using a neat little IR chip.

If it works out well, would you mind me selling a few kits? ;)

Steve Conner

Tue Jul 22 2014, 07:01PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Latest (4th) test run was a success! I got an arc of 8ft (2.4m) which is a new personal best.

Output was limited by ceiling height again.

After the last blowout, I rebuilt the bridge using surplus SKM400GB123D bricks with 3.3 ohm gate resistors, and increased the current limit to 1kA. I carefully tuned the phase lead and deadtime while running at high current with the primary coil only. Then I kludged an extra turn onto the primary and made a second topload (8" x 36" approx) from aluminium ducting.

I then rolled it out for another test run with my evil henchman Jim, and Alan, one of the original pioneers of solid-state coiling. We started with the same configuration as the end of the previous run: single topload and 5 primary turns. Even though the primary current was increased, the spark length stayed much the same. Fiddling with the primary tapping point didn't seem to have much effect. I also wanted to try the lower pole frequency, but the PLL refused to lock to it reliably for some reason and fiddling with the primary tap didn't help at all.

Then we added the second topload and the new 6th primary turn. This made a dramatic difference to the output, I now got regular arcs to the floor and ceiling 8ft above. It also hit a strike target positioned 8ft away horizontally. We ended the tests due to worries about burning the floor or damaging stuff inside the suspended ceiling.

The output from the Rogowski coil was quite hard to analyse due to noise that was getting into it from somewhere. But it looked as if the PLL driver's control of soft switching was just "meh". Not so bad that it would blow something catastrophically, but not tight enough for really low switching losses. I think a phase lead driver could do better, so I won't recommend the PLL for ordinary DRSSTCs any more. For higher impedance, tighter coupled coils, and for QCWs and SSTCs where you want to modulate the phase shift, it works great.

Anyway, to the moon!

1406055696 30 FT4896 Odin Test Burntisland A1

1406055696 30 FT4896 Odin Test Burntisland1

1406055696 30 FT4896 Odin Test Burntisland2

Mads Barnkob

Tue Jul 22 2014, 07:28PM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

Finally!

Congratulations on landing it after only 8 years, 4 months and 2 days! I certainly hope I make it before that, I am already at 2Â½ years and assembly is not done yet :)

Are you going to do further pushing somewhere with more room for hot sparks?

Steve Conner

Tue Jul 22 2014, 09:13PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

This thread has 1 page for each year.

Yes, we will take it back to the warehouse in Glasgow that was used for test run 3, but we might have to wait until the Games are over.

I will also have to get it playing the obligatory chiptunes, and maybe build a bigger bridge as I think the resonator is too big for the current one.

Linas

Tue Jul 22 2014, 10:17PM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

where did you get, and how does it cost to get aluminum toroid, i want one for my coil :(

Sigurthr

Tue Jul 22 2014, 10:23PM

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

Awesome! Congrats! It's about time you get some sweet success after so much work has been put in.

Steve Conner

Tue Jul 22 2014, 10:33PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

These toroids were a bulk buy by the Tesla Coil Builders of the UK many years ago. We paid Â£90 each and had them custom made by a metal spinning company. Unfortunately it is too small for the new coil :(

Uspring

Wed Jul 23 2014, 10:47AM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
Location:
Posts: 711

Spectacular

You must have chnaged the frequencies quite a bit by adding the top load. Do you have any data on that? From the sound of the sparks it seems, that you are also using long bursts?

Wrt to the PLL driver: Too bad you couldn't make it work on the lower pole. It would have been interesting to get a side by side comparison of lower and upper pole operation. I'd expect to see the primary current peak to appear much more in lower pole mode. Your driver probably wouldn't be affected so much by it, since it would go into pulse skipping mode to get by it rather than by terminating the burst when it hits the OCD condition.

Steve Conner

Wed Jul 23 2014, 11:48AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

The upper pole frequency was 89kHz with one topload and 74kHz with two.

Burst length was varied between 150 and 300us during the video.

I don't know why the lower pole wouldn't work.

Linas

Thu Jul 31 2014, 08:45PM

Registered Member #1143 Joined: Sun Nov 25 2007, 04:55PM
Location: Vilnius, Lithuania
Posts: 721

Since i am reworking my coil MMC capacitor, you told in other thread that 0,7uF was too large .

What would you recommend for 50kHz coil running on CM600HA-24H bull bridge ?

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