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Hammertone "Predikter", the DRSSTC driver for the rest of the century.

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Dalus

Mon Jun 15 2009, 10:08PM

Registered Member #639 Joined: Wed Apr 11 2007, 09:09PM
Location: The Netherlands, Herkenbosch
Posts: 512

Starting to look good

Nice to see you're able to run with the electronics in the open without shielding.

I've tried a similar gate driver on my coil some time ago without your predictor schematic. My gate driver was just a halfbridge of irfp450's running on 350Vdc with a step down gdt on each IGBT. This did not change the currents or the performance of the coil when compared to high side drive. So it's quite a nice solution when you need to drive multiple brick IGBT's. (btw I tested it on 2 CM300 igbt's) And I plan to use it on a dual H-bridge with 4 cm-300 modules.

Anyway keep up the good work, I'm still considering to try it on my coil to see how it affect performance. Though that will be in the future.

Still very curious to see what you guys and your coil can do

Finn Hammer

Tue Jun 16 2009, 11:44PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Today we (Daniel and I) worked till the blod was squirting from our nails, to finish a new primary coil, a bigger topload, and a voltage doubler too.
Goal: To make as much spark as possible.
We did not have time to reconfigure the current transformers, so we were limited to 1400Apri. which corresponds to 7V on pin 3 of IC8, the AD790 down in the current controll deck. With 1:100 current transformers, that is.....
It's as easy as that: just dial the right voltage, and we have predictable over current protection. No experimenting, here.
We also did not have time to make snubbers, but then did not seem to need them: We were running 800V into the bridge, switching 0 current, but peaking 1400A and making 2.5 meters of spark. That's 8feet4 to you yanks.
It was a bit windy, and we had only 10A 240V so mainly bursts.
The primary capacitor was 0.75uF and Fres 32kHz.
The "predikter" was out in the open. Not even a ground connection has been routed out to it, it is just floating out there.
I think Daniel is making a small video from this evening right now.

Enjoy

Cheers, Finn Hammer

Coronafix

Tue Jun 16 2009, 11:54PM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Well, well. Bloody nice work both of you!!

Dalus

Wed Jun 17 2009, 09:00AM

Registered Member #639 Joined: Wed Apr 11 2007, 09:09PM
Location: The Netherlands, Herkenbosch
Posts: 512

Nice results guys, glad that your r&d led to something useful to the whole community. Think I'll redesign my controller to incorporate your predikter after all. I'll keep you updated on how it works out for me. Will take a long time to complete though since I don't have money for a new MMC atm though I'm working on that problem literally.

Anyway still looking forward to see how it preforms on a 3~ 32A line

btw Finn you where the one that could buy those brass bolts? If so would like to buy some from you for my coil.

Finn Hammer

Wed Jun 17 2009, 06:45PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Dalus wrote ...

btw Finn you where the one that could buy those brass bolts? If so would like to buy some from you for my coil.

Dalus,

Thanks for youir kind comments.

About brass bolts. I am not against going a bit out of my way to help a fellow coiler in a tight spot, getting parts. Being situated in the old "east" may be such a tight spot.
But in the Netherlands? I would assume that the local Bauhaus has them on a rack. Have you checked?

Cheers, Finn Hammer

Linas

Wed Jun 17 2009, 08:37PM

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

Have you oscillation start in your circuit ? because i have some problems with my driver startup, need some frequency to start oscillate, and just then feedback catch the frequency of primary.

Finn Hammer

Wed Jun 17 2009, 08:55PM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

Linas wrote ...

Have you oscillation start in your circuit ? because i have some problems with my driver startup, need some frequency to start oscillate, and just then feedback catch the frequency of primary.

No. The bridge starts to conduct when the interuptor is *on*, then switches at the zero crossings untill the interuptor is off, and then stops at the next following zero..

Sounds like you need to reverse the current transformer.

You are running standard Ward controller?

Cheers, Finn Hammer

GeordieBoy

Wed Jun 17 2009, 09:31PM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

Finn, that video is awesome! Particularly the longer bursts at the end where you vary the break rate. It's good that you have found the phase-lead network to improve operation. The sparks look really fat and bright too. What was the burst length set to during your video?

-Richie,

Dalus

Wed Jun 17 2009, 09:42PM

Registered Member #639 Joined: Wed Apr 11 2007, 09:09PM
Location: The Netherlands, Herkenbosch
Posts: 512

Finn Hammer wrote ...

About brass bolts. I am not against going a bit out of my way to help a fellow coiler in a tight spot, getting parts. Being situated in the old "east" may be such a tight spot.
But in the Netherlands? I would assume that the local Bauhaus has them on a rack. Have you checked?

Cheers, Finn Hammer

No haven't checked them yet. I'll sure do. I've searched quite a while myself but couldn't find a company that offers them. Thanks for the tip

Finn Hammer

Thu Jun 18 2009, 05:08AM

Registered Member #205 Joined: Sat Feb 18 2006, 11:59AM
Location: SkÃ¸rping, Denmark
Posts: 741

GeordieBoy wrote ...

Finn, that video is awesome! Particularly the longer bursts at the end where you vary the break rate. It's good that you have found the phase-lead network to improve operation. The sparks look really fat and bright too. What was the burst length set to during your video?

-Richie,

Thanks!

Yes we were quite exited, also since my own spark length record was set 10 years ago, 2.4 meters on the prototype of the old Museum coil.

We were at times using as high as 300ÂµS with good results, which surprised me, since 200ÂµS usually seems to be the prime duration.

Daniels motor is now going to pass 3 months testing, as it is on display (in a proper faraday cage, for some children fare at the university). Great chance for some long time tests, although at reduced power.

Cheers, Finn Hammer

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