Middle sized DRSSTC upgrade for IGBT bricks

[Rapy2]

Hi there,
2 months ago I finished my middle sized DRSSTC. I wrote about it in my last post. It worked very well for that size, the maximum measured discharges were up to 2 meters, which is almost 5 times longer than the secondary coil. But the problem is, that it is double bridge made of HGTG30N60A4D (TO-247 package). I've already destroyed my bridge 2 times due to a stupid mistake. And that's how I realized how bad this solution is. It was running it at 125 khz, 750A OCD limit, 90 us ontime, about 400 BPS and rectified mains voltage 325V bus.

Now I want to rebuild it for IGBT bricks, but I can´t afford buying new IGBT bricks for hunderds of dollars. So I am looking for some used bricks. I found SKM200GB128D for good price, but I am not sure if it will be fast enough for 125 khz. Therefore, I would like to ask if they can handle 125 khz at around 700A. I also looked at Mads website for his brick table, but I couldn't find any of these bricks at a reasonable price. Or do you have any other suggestions which bricks I could use? Thank you very much

[oneKone]

I've had awesome success with buying semikron bricks from AliExpress (bizon tech is a good seller). I run skm200gb125d half bridge modules in one of my full bridge drsstc. I think* it's currently running at 140khz, upto 1.4ms on time, bps I've never looked, 600apk, RMS draw is 4.6kw. I'm confident an skm200 will.suit your needs perfectly.

[AstRii]

it's currently running at 140khz, upto 1.4ms on time, bps I've never looked, 600apk, RMS draw is 4.6kw.

Good stuff. I'm planning a very similar DRSSTC long pulse twins. Do you think that water cooling of the primary coil is necessary at these ontimes?

[alan sailer]

Good luck with you brick adventures.

You mentioned that you accidentally destroyed your parallelTo-247 bridge twice. I like to learn about issues (so that I don't make
the same mistakes) so I am curious what you did that killed the bridge?

Cheers.

[oneKone]

Cheers @AstRii.

So far I haven't had any problems with excessive primary heating, although my run times are only a few minutes.

[Rapy2]

Hi oneKone, thank you for your reply. I ordered skm200gb125d 3 days ago, so I like to hear that they are nice 

[Rapy2]

Hi, yeah I killed it due to a stupid mistakes. First time I wanted to discharge my capacitors, so I unplugged it from mains and didn't realize that secondary coil is not grounded anymore. When I switched on the interrupter, there were some random noises of high voltage and then boom.

Second time arc strikes to a MMC, I didn't have any proper strike rails. And then boom again.

I like to learn about issues (so that I don't make
the same mistakes) so I am curious what you did that killed the bridge?

[alan sailer]

PApy2,

Thanks for the info. I wouldn't call either death stupid because they were not that obvious to me. So I learned something.

I do the same sort of stuff about backpacking accidents, reading carefully to see what went wrong. Sometimes it's just random crap
that you can't predict but other times it's pretty preventable as long as you know what to watch for.

Good luck with your new bricks. The two things I enjoyed about the SKM100 I used was a) the 1200 volt left me plenty of margin and b)
the bigger brick size left lots of room for other parts. The physical layout was much easier.

Cheers.

[Rapy2]

Thanks Alan,
bricks are on the way to me. I am really looking forward them.

Good luck with your new bricks. The two things I enjoyed about the SKM100 I used was a) the 1200 volt left me plenty of margin and b)
the bigger brick size left lots of room for other parts. The physical layout was much easier.

Cheers.