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Odin The All-Fragger: my unfinished DRSSTC

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Steve McConner

Sun Mar 19 2006, 06:37PM

Joined: Fri Feb 03 2006, 04:52AM
Location: Glasgow, Scotland
Posts: 3930

Update, November 2007-

Unfortunately the sale fell through due to me not being able to get it built on time, not to mention worries about reliability. All I can say is that it will "Maybe" get finished "sometime" :|

Update, September 2007-

Well, I've had a fairly serious offer from a sponsor who wants to buy the drive electronics from Odin and make their own resonator to go with it. So, I've decided to get back to work! If it falls through, I'll try to bring it to Cambridge instead, and maybe hook it up to someone else's resonator.

I finished rewinding and wiring up all the drive transformers, and all four drivers appear to be good. I connected two of the drivers to a spare Semikron 300A halfbridge IGBT brick for testing.

The drivers hooked up. Yes those are Cat5 cables.

Gate waveforms, check. The top waveform is the trigger reference from the signal generator, the lower two are the gate voltages. We are driving the two 300A IGBTs CW at 25kHz, to +24 and -12V.

I hooked the halfbridge up to a ferrite transformer from an electronic NST, and fed it with 20V DC. It made a nice spark. This is possibly the most overkill flyback driver ever.

Oh noes! The transformer is on fire.

What's the matter, little transformer? 300A IGBT brick too much for ya?

This proves that the gate drivers work, at 20V DC bus voltage at least! The finished coil will operate at 600V DC bus, so I still have some way to go...

Update, June 2007-

I tried Hi-pot testing the new gate drive boards, and the results were dramatic. The isolation transformers were destroyed completely! :(

So I tried a new GDT design using Kynar wire on Teflon wrapped cores. It easily survived a zapping with a MOT! The scope trace shows the voltage across it taken with a 100x probe.

I bought some more Kynar wire and made eight of these new GDTs, but haven't got round to fitting them to the boards yet.

I also have some plans for a fibre optic link using Toslink parts, inspired by jrz126. I plan to use three fibres to transmit the interrupter signal, the DC link voltage control signal, and the PLL fine tuning signal. I was going to multiplex the signals using chips designed for digital audio, but it seems less hassle (and less chances for EMI to crash things!) if I just use three copies of jrz126's circuit.

Update, March 11 2007-

After a long time off this project, I got back on it by building another two gate drivers. I now have a complete set together and working. I'll hi-pot test them tomorrow with a MOT or whatever.

Things I still need to do: Build the "hub" that connects all the Cat5 cables to the PLL driver, with the inverter in it that supplies power to the gate driver boards. Hook the SCRs in the voltage doubler up, and modify the SCR driver for more current. Hi-pot test the dodgy looking insulation in the H-bridge. Wire up all the power wiring and meters. Hook the IGBTs up and test the drive. Fix the secondary. Build a new primary. Sort out the tank capacitors. Get some kind of fibre optic system to control it all. Etc.

Update July 8 2006-

I built another brick driver and compared the outputs from both of them.

Outputs at 200kHz with deadtime control turned to minimum.

Same with deadtime turned to max. The deadtime looks a little uneven, but that shouldn't be a problem at the lower frequencies I would use bricks with. I'm just using 200kHz because that's what the PLL unit from my other coil is set to, and I can't be bothered opening it to change it.

Update July 1 2006-

I got the H-bridge and meters bolted onto the old wooden frame from the OLTC 2.

I also replaced the OLTC 2 single turn primary with a rough 9 turn coil, but I don't have a picture of that. (It looks terrible.) I wound a couple more of the signal and power isolating transformers too.

Update on June 17 2006-

I finally managed to get one of the boards built and hooked up to a power supply and gate drive. It seems to work as planned, though I bought the wrong ribbon cable connectors to hook it to the IGBT properly. Also, I can't test the undervoltage lockout, because I forgot to get the right zener diodes for it.

The power isolating transformer's core gets a little hot, so it probably needs more turns.

other minor oops-ups:
-Got the cores mixed up in the Cat5, so the HF power is twisted together with the UVLO signal.
-Never noticed that the MOSFETs I bought aren't actually in D2pak footprints. They still sort of fit, anyway.

finished board

scope screenshot shows the gate of a 600A IGBT being driven with +24 and -12v at 200kHz. >_< The second trace shows the zero volts level.

board had to be kludged onto IGBT with two short pieces of wire.

Update on May 14 2006-

The boards are back from Gold Phoenix, omg omg! There will now be a short interlude while I build a set up, bolt them onto some IGBTs, and test them. Assuming they work, I plan to sell all the extra boards I don't need to you guys

Update on April 13 2006-

I finished the outboard driver PCB, got the safety clearances as big as I could, and generated the Gerber and drill files for it. I just need to revise the main PLL board to get rid of all the bugs that were in the last version. I should have the board order placed with Gold Phoenix by the end of today.

a paper mockup of the board to check component footprints

Now I've nearly got the outboard drivers done.

schematic. Note the optoisolators that act as undervoltage lockout, Richie Burnett persuaded me to put these in.

preliminary PCB layout (still got to check safety clearances)

The first step was to build the H-bridge.

I'm going to try attaching about a dozen pictures to this and see if it works.

four big inverter grade capacitors (3300uF @ 420V). The tops are wrapped with electrical tape to reduce the chance of the metal can coming into contact with the metal case I'm using to hold them.

two 300A 1200V half-bridge IGBT modules and one half-bridge SCR module for soft-start and DC voltage control

Don't ask what the insulation is made out of.

These funny shaped busbars connect the IGBTs to the capacitors with minimum stray inductance.

like so

The HF output terminals on the bricks aren't connected to anything yet.

woot!

This thread continues from

on the old board.

"Common sense is holographic and common sense itself should tell you that." - the late Chris McKinstry
don't forget to visit the scopeblog!

Blackplasma

Sun Mar 19 2006, 10:09PM

Registered Member #63
Joined: Thu Feb 09 2006, 12:18AM
Location:
Posts: 1417

I love it Steve!

How are you driving the bricks, and what model are they? I've got some semikron bricks that look like that... muahaha.

Steve Ward

Sun Mar 19 2006, 11:50PM

Registered Member #146
Joined: Sat Feb 11 2006, 10:21PM
Location: Streamwood, IL.
Posts: 907

Excellent. You always go out of your way for these ultra low inductance designs but... shouldnt it be soft switching anyway?

. Hey, where are your low inductance decoupling caps? Or ar those lytics so good that you dont need them? I expect at least 10 feet from a coil driven with that monster of an inverter! Good luck.

Marko

Mon Mar 20 2006, 03:21AM

Registered Member #89
Joined: Thu Feb 09 2006, 08:40AM
Location: Zadar, Croatia
Posts: 2600

The last picture is the best...
Nice huge heatsink, you can build entire DRSSTC on it itself

Im troubling myself to find anything larger than small CPU cooler, maybe few rusty TO3 heatsinks. Not to talk about 40N60s, TVS supressors...

Good luck then

Steve McConner

Mon Mar 20 2006, 06:54AM

Joined: Fri Feb 03 2006, 04:52AM
Location: Glasgow, Scotland
Posts: 3930

Hi guys, thanks for the feedback! The "Nice large heatsink" was donated by Finn Hammer, its name is Finn's Fins.

blackplasma: The bricks are Semikron part# SKM300GB123D. I managed to get hold of the 400A version too, but I'm saving them till I've pop popped all the others

I don't know if anybody has used these in a DRSSTC before but I reckon they should work fine. If not, I tried to make sure the layout would fit the Powerex F and H series bricks too. I'm driving them with my PLL driver through a set of outboard gate drivers that I documented on my site.

steve: I was discussing this with Richie a while back. He said that commercial SMPS often just use the electrolytics on their own, and also I had trouble with resonances caused by the plastic film bypass caps on my last DRSSTC. So I'm going to try leaving them out this time. That's why I wanted the low inductance busbars, to get the electrolytics "closer" to the IGBTs so they would be effective. I think they have about 25nH ESL which is about average for inverter grade caps. I'll check the DC bus for spikes when I test it, and if necessary I'll add some caps in.

"Common sense is holographic and common sense itself should tell you that." - the late Chris McKinstry
don't forget to visit the scopeblog!

vasil

Mon Mar 20 2006, 07:25AM

Registered Member #229
Joined: Tue Feb 21 2006, 01:33PM
Location: Romania
Posts: 453

woot
If it will run OK, I will buy my own semkrons to build another drsstc.

Good luck Dr Conner!

Sparking all the time

Hazmatt_(The Underdog)

Tue Mar 21 2006, 05:51PM

Registered Member #135
Joined: Fri Feb 10 2006, 06:06PM
Location: Stanton CA.
Posts: 1298

You might want to switch out your cap stud screws from black phosphate SHCS for Stainless.

"Our five year mission to find new answers, methods and determinations to solving old problems with Tesla Coils, to seek out new simulations and approximations.... To Boldly go where no amature has gone before!" *intro Star Trek theme*

*guess im over the whole website loss thing by now... now to get $$ for a website...mmm*

Steve McConner

Tue Mar 21 2006, 06:09PM

Joined: Fri Feb 03 2006, 04:52AM
Location: Glasgow, Scotland
Posts: 3930

Why? Everyone should be too busy looking at the sparks to notice that my cap screws aren't shiny.

All kinds of steel are lousy conductors of high frequency current, so I arranged it that every joint has direct copper-to-copper contact (or copper to aluminium in the case of the capacitor teminal posts) and the screws are just for clamping force.

Non-magnetic stainless isn't too bad- they make radio antenna whips out of it after all- but it's still not as good as brass, copper, or aluminium.

"Common sense is holographic and common sense itself should tell you that." - the late Chris McKinstry
don't forget to visit the scopeblog!

Hazmatt_(The Underdog)

Wed Mar 22 2006, 12:11AM

Registered Member #135
Joined: Fri Feb 10 2006, 06:06PM
Location: Stanton CA.
Posts: 1298

*shruggs* I was just trying to consider how much current will go through the stud as opposed to the terminal face as opposed to current going through both. Not that I was worried about shiny, or cost, or corrosion or whatever.

Steve McConner

Wed Mar 22 2006, 04:12AM

Joined: Fri Feb 03 2006, 04:52AM
Location: Glasgow, Scotland
Posts: 3930

I was kind of assuming that it would more or less all go through the terminal face since copper conducts so much better than steel. But I'll keep an eye on the screws and see if they do get hot, if so, I'll change them for some other material like non-magnetic stainless steel or brass. Not that I've ever seen a socket headed cap screw made of brass

"Common sense is holographic and common sense itself should tell you that." - the late Chris McKinstry
don't forget to visit the scopeblog!

Sulaiman

Wed Mar 22 2006, 04:32AM

Registered Member #162
Joined: Mon Feb 13 2006, 04:25AM
Location: England
Posts: 1220

just wanted to add my admiration!
a very nice layout / construction.
I like the way you minimise inductance
I've had wires going through heatsinks to attempt the same, not very good

good luck (though you need it less than most of us!)
and keep us posted.

2EOYAH
I have learned much more from my failures than from my successes.
I just wish I could remember what I've learned.

Adam Horden

Wed Mar 22 2006, 08:15AM

Registered Member #176
Joined: Tue Feb 14 2006, 03:35PM
Location:
Posts: 44

Hi Steve,

Nice work looks very professional. Are those lytics in half a RS equipment enclosure? I have seen something simular shappped with the cut outs on the side in the RS cat.

At least some one is finally using some of the lytics I had and a big coil is been built!

How are you connecting the gate drive to the bricks?

Adam

Steve McConner

Wed Mar 22 2006, 10:05AM

Joined: Fri Feb 03 2006, 04:52AM
Location: Glasgow, Scotland
Posts: 3930

Hi Adam

Yes it's an old case from RS

I got it from a junk pile at the uni. It seems like a weird way to mount the caps, but it actually worked out easier than buying the big oversized capacitor clamps and cutting big holes in a piece of sheet metal.

I'm using outboard gate drivers, they will connect to the IGBTs via about 4" of ribbon cable with alternate cores connected to gate and emitter to give extra low inductance... I don't do the I word man

It turned out too much of a hassle to mount the drivers straight to the IGBTs, considering I want to use the same gate driver boards with CM600s in the future, and their gate terminals are in totally different places.

The drivers will connect back to the PLL unit using Cat5 network cables with the little 8-way modular jacks because they're cheap.

"Common sense is holographic and common sense itself should tell you that." - the late Chris McKinstry
don't forget to visit the scopeblog!

Adam Horden

Wed Mar 22 2006, 02:10PM

Registered Member #176
Joined: Tue Feb 14 2006, 03:35PM
Location:
Posts: 44

Hi Steve,

**digs out notebook**

Its a nice idea and all your layouts look really low inductance. Do you apply the math to work out the actual inductance of the layout? I tried it on the one I will discuss below but I got really small numbers and decided that those could not be right!

I have all the parts to still build a big CM600 bridge. The modules would be built with smds and inside a can with BNC connectors to connect them to the driver and would bolt direct to a CM600.

The layout I decided on was simular to yours but imagine it been on its side with the bridge flat.

The bridge was a huge long length of heatsink like on your OLTC2 the same stuff. The bricks would have a laminated bus scheme but the caps on there side and bolted in mid air across the laminate. You end up with 6 electrolics across a low inductance laminate bus scheme. The DC in would bolt direct to a IRPACK SCR moudle the dual ones. Eveything lies flat with the caps horizonal to the bricks that are vertical.

The whole system would of been nice to build with lots of thick copper busbar. I also designed in a method of mounting polyester excel decoupling caps in there.

I still have 6 brand new cm600s and most of the design work done on the bridge. And I think I have a tray of caps left.

Adam

Steve McConner

Mon Mar 27 2006, 04:31AM

Joined: Fri Feb 03 2006, 04:52AM
Location: Glasgow, Scotland
Posts: 3930

Hi Adam

No I don't calculate the inductance. I just know that the less area enclosed by the loop that the current flows in (ie the closer together the conductors are) the better. It doesn't really take much more effort to make a low inductance layout than an ordinary one.

If you want to build a 600A bridge for "Team Odin" you would be more than welcome! We could fire it up at Cambridge sometime. I think they can bring in 400V three phase power for us without too much hassle.

"Common sense is holographic and common sense itself should tell you that." - the late Chris McKinstry
don't forget to visit the scopeblog!

Part Scavenger

Tue Mar 28 2006, 09:46PM

Registered Member #79
Joined: Thu Feb 09 2006, 05:35AM
Location: Arkansas
Posts: 661

OH YEAH! This is gonna be good. Doc Conner building another DRSSTC!

I look forward to this. You do great work man!

/*drooling over setup*

Just doing my part to help replenish the ozone layer.
Coming soon:

Old Site Mirror:

Adam Horden

Wed Mar 29 2006, 05:17AM

Registered Member #176
Joined: Tue Feb 14 2006, 03:35PM
Location:
Posts: 44

Steve Conner wrote ...

Hi Adam

No I don't calculate the inductance. I just know that the less area enclosed by the loop that the current flows in (ie the closer together the conductors are) the better. It doesn't really take much more effort to make a low inductance layout than an ordinary one.

If you want to build a 600A bridge for "Team Odin" you would be more than welcome! We could fire it up at Cambridge sometime. I think they can bring in 400V three phase power for us without too much hassle.

Hi Steve,

I will build up a bridge with the parts I have.

Adam

Steve McConner

Sun Apr 02 2006, 06:12PM

Joined: Fri Feb 03 2006, 04:52AM
Location: Glasgow, Scotland
Posts: 3930

I've updated the first post with details of the new driver boards.

"Common sense is holographic and common sense itself should tell you that." - the late Chris McKinstry
don't forget to visit the scopeblog!

robert

Mon Apr 03 2006, 12:23PM

Registered Member #188
Joined: Thu Feb 16 2006, 11:18AM
Location:
Posts: 67

Wow, looks nice.
Though i would do something about getting better isolation barriers, i always like to have at least 8mm for anything line-connected (well, might be because im currently doing PCB layouts for off-line SMPS things).
So id use optos with 10.6mm lead spacing (like PC817 or CNY81) or just bend your standard DIP to this larger spacing.
To save space, use 4-pinned ones, also reduces the chance of EMI pickup on the base lead (can be a large problem in noisy environments).

Steve McConner

Sun Apr 16 2006, 06:51AM

Joined: Fri Feb 03 2006, 04:52AM
Location: Glasgow, Scotland
Posts: 3930

Update: I finished the gate driver layout and also revised the main PLL board layout, and ordered a batch of each from Gold Phoenix. I expect to get 8 PLL boards and about 30 gate drivers.

Robert: I chose to use 6-pin optos because they bring the base lead out, so I could tie it to the emitter with a resistor in an attempt to make it less sensitive to EMI. :P And because 4N35s are pretty cheap I suppose.

"Common sense is holographic and common sense itself should tell you that." - the late Chris McKinstry
don't forget to visit the scopeblog!

Steve McConner

Sun May 14 2006, 11:33AM

Joined: Fri Feb 03 2006, 04:52AM
Location: Glasgow, Scotland
Posts: 3930

Update: Boards are back! Just got to stuff and test them. I updated the first post with a picture.

"Common sense is holographic and common sense itself should tell you that." - the late Chris McKinstry
don't forget to visit the scopeblog!

Marko

Sun May 14 2006, 11:40AM

Registered Member #89
Joined: Thu Feb 09 2006, 08:40AM
Location: Zadar, Croatia
Posts: 2600

Very nice! When will somebody make homemade board like theese..

EastVoltResearch

Tue May 16 2006, 07:35PM

Joined: Thu Feb 02 2006, 07:11AM
Location: Philadelphia, PA
Posts: 2408

Its ashamed you are no longer interested in coils . . .

DRSSTC, SSTC, HV Educational Kits and Parts
http://www.easternvoltageresearch.com
Be sure to check out our student sponsorship program!

Marko

Wed May 17 2006, 09:30AM

Registered Member #89
Joined: Thu Feb 09 2006, 08:40AM
Location: Zadar, Croatia
Posts: 2600

Steve, may I ask a question: What is additional 'UN10KN' mosfet used for?
Couuldn't you drive both of gate mosfets just simply from GDT?

(or im' most probably missing something) ?

Steve McConner

Wed May 17 2006, 11:00AM

Joined: Fri Feb 03 2006, 04:52AM
Location: Glasgow, Scotland
Posts: 3930

Dan: I quit doing the DRSSTC theory because it was making my head hurt and not going anywhere. I also decided to quit exhibiting at teslathons because of the money and hassle, and I decided not to try and beat Steve Ward's spark length record for the same reason. I guess I basically did all this stuff just to show off, and I can't be bothered any more.

However, I have a lot of IGBT bricks and capacitors stacked on top of my kitchen cupboards now, and I don't see any reason not to have some fun with them

Firkragg: If I drove both MOSFETs directly off the GDT, then they would both be "off" in between bursts. Then the IGBT gate could theoretically float to any voltage it liked. The VN10KM FET and its associated components are just an inverter that makes sure the bottom MOSFET stays "on" between bursts and clamps the IGBT gate to -12V. I tuned the component values so there would be no shoot-through between the two MOSFETs.

"Common sense is holographic and common sense itself should tell you that." - the late Chris McKinstry
don't forget to visit the scopeblog!

Marko

Wed May 17 2006, 03:20PM

Registered Member #89
Joined: Thu Feb 09 2006, 08:40AM
Location: Zadar, Croatia
Posts: 2600

I'm an idiot.
What I tought was to connect Vcc rail to another leg of GDT to open the MOSFET by default, but I was faster in writing this than figuring out it will turn in chaos at end of burst. (inductve kick on secondary would mess up the thing).
Inverter is rather a better idea.

Steve McConner

Wed May 31 2006, 03:43PM

Joined: Fri Feb 03 2006, 04:52AM
Location: Glasgow, Scotland
Posts: 3930

Update on progress. I'm currently ordering parts to finish the new boards, both for myself, and a few other people. I sell a pack of all the parts you'll probably have trouble getting and won't know how to substitute.

The PLL boards are all sold now, unless someone cancels an order.

"Common sense is holographic and common sense itself should tell you that." - the late Chris McKinstry
don't forget to visit the scopeblog!

Steve McConner

Sun Jun 18 2006, 02:38PM

Joined: Fri Feb 03 2006, 04:52AM
Location: Glasgow, Scotland
Posts: 3930

OMG update. Don't tell me the creepage distances are too small.

"Common sense is holographic and common sense itself should tell you that." - the late Chris McKinstry
don't forget to visit the scopeblog!

Blackplasma

Mon Jun 19 2006, 02:40AM

Registered Member #63
Joined: Thu Feb 09 2006, 12:18AM
Location:
Posts: 1417

Gorgeous, Steve!

Your boards are considerably more complex than my isodriver system, too ^^

Mine are crammed as closely together as non-surface-mount components permit. Even with a double-sided board, you couldn't get them closer =D It's a great feeling, and a topological nightmare, but I just love the spatial thinking involved.

...all I need now is pics... and not to hijack your thread.

What silicon are you using to drive the isolated power supply / ferrite?

I'm guessing for all the 'signal transformers' you're just using donut cores?

Steve McConner

Mon Jun 19 2006, 04:32AM

Joined: Fri Feb 03 2006, 04:52AM
Location: Glasgow, Scotland
Posts: 3930

Hi BP

I never crammed my components that tightly. I planned to get it all on to a quarter Eurocard, but I had to lengthen it a bit. I had to leave room for the silkscreen, and even so, I had to put some of the component names under the components.

For the power supply I'm using two of the same STD12NF06 MOSFETs that I bought a pile of for the drivers.

The signal transformers are more ferrite sleeves really, they're a bit tall to be "donuts". I chose them because they were in the RS catalogue and looked about the right size. :P

"Common sense is holographic and common sense itself should tell you that." - the late Chris McKinstry
don't forget to visit the scopeblog!

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