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First real DRSSTC

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Mon Nov 03 2008, 02:37PM

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

Anders M. wrote ...

This

seems like the simplest way to gate-drive CM300s.

Anders M.

Little off topic: It might be the best way for *SSTCs but I doubt you will find any commercial equipment with large IGBTs driven directly from a GDT.

Dalus

Mon Nov 03 2008, 03:23PM

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

I'm also not very sure if driving the igbt's with a GDT would work. The method Steve Ward used in his new driver also worked well in my small 1.4Mhz sstc. It looks like Steve Ward is using a GDT to drive his bricks on the driver page

But I'm still not sure if it's worth the effort to build a high side gate driver. In my case I'd need eight of them. I'm going to parallel two cm300 H-Bridges via two inductors to get even current sharing.

Reaching

Mon Nov 03 2008, 06:25PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

You can drive large igbt bricks even with small core sized gdts. what i can say is, that i havent had any problems in driving bricks with simple gdts even when using ucc drive ics. i cannot say that the cm300 igbts are my favourites cause they are relatively old technology compared to the newer generations of igbt bricks. so they have a big, and i mean really big gate capacitance which makes them hard to drive via gdt. a cm300 brick has around 80nF gate capacitance. compared to a skm module with the same or better specs, the gate capacitance of the cm module is 3 times bigger.

when driving via gdt i would go for some siemens bsm modules or semikron skm series. eupec has some nice bricks for smaller sized drsstcs. here in germany cm modules are hard to find and they are very expensive. for comparisation. a cm300 module would cost me around 60â‚¬. a skm400 half bridge module with better specs and lower gate capacitance would cost me no more than 30â‚¬..

Dalus

Mon Nov 03 2008, 06:32PM

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

Ok I'll try it with a GDT first. I can't go for other IGBT's. I already ordered four CM300DY-24H from bsr-elektronik for this project. We'll see how it goes with a GDT first.

If it doesn't work out well I'll just build a few high side drivers.

Steve Conner

Mon Nov 03 2008, 06:37PM

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

The SKM modules come in different series. I have some 3 series (the SKM300GB123D and SKM400GB123D) and they seem about the same as the Powerex H-series in performance. Which ones do you have Reaching?

Reaching

Mon Nov 03 2008, 11:27PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

i have some skm600gb121 modules here. but they are expensive and hard to get. third series i think. then i have some skm200gb123d modules and some skm400 of the same type, both halfbridge modules third series. for my last commercial drsstc i used brand new skm400gb 4th series modules with new semitrans standard. this drsstc is still alive, every day duty for a year now!
really expensive, around 300bucks for one of those new modules, but the performance i good and they are really hard to destroy even in heavy duty apps like drsstcs etc. the gate cap is much less than in the 3th series. but the specs in the datasheets are not conform with the measurements i got for the gate cap. for the 3th series skm400gb modules the capacitance of a single gate was 26nF, the 4th series module had only 16nF, and that with way better specs in rise and fall times.
those modules are easy to drive via a gdt up to 100khz and above without much problem. with good snubber caps and a big dc filter cap there was no ringing nor much heat dissipation because of switching transitions etc.
i havent tested the cm modules yet, but i doubt they are much better than the skm or bsm series i like to use. of course, they are much cheaper and easier to get.

Dalus

Thu Nov 13 2008, 08:41PM

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

I did the last test with the isoplus IGBT's. I wanted to know at which current they would fail, It turned out to be 400A with a nice bang. So the ocp is going to be set on 300A for the final isoplus coil. It's going to be demoed at my school. And afterwards it's going to be rebuild with the dual CM-300 H-bridge, those bricks look nice

Here's a picture of the exploded IGBT:

And the bang on video, the coil did 95cm streamers at 300A

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