OCD limits based on Semikron IGBTs

[Felix M.]

Hi all,
I'm Felix, 17 from southern Germany.

After building my first SGTC and SSTC I recently started on my first DRSSTC based on two SKM200GB128D in a H-bridge configuration.
(I got a qiute cheap offer on a total of 4 IGBTs on ebay so I decidet to start building the DRSSTC.)
I will run it from rectified 3 phased AC to get a busvoltage of 565VDC.
Since the whole thing is slowly comming together I started to think about the maximum current the IGBTs could handle.
Does someone have a recommendation or even some experience with this IGBT type and the current limmits?

Greetings

[All Science]

In a DRSSTC the combination of soft switching and low on times generally allow for the IGBTs to handle more current then is listed in the datasheet. It depends on multiple factors though, like the IGBTs speed relative to your coils resonance frequency, bridge design, and the type of driver (if it has phase lead or not for example), just to name a few. I've seen 200A IGBTs similar to yours pushed to 900A, and I've also seen them fail at 500A or even lower. If you think you have a decent low inductance bridge layout, then over 600A can be reasonable. But yeah, it depends on your coil, but to play it safe 600A-800A is probably the max I'd do for those. Although, I assume you'd probably want more if you're running your coil on 3 phase power. As long as it's under the value I mentioned it'll probably be fine. But I wouldn't set the OCD this high if you'd never expect it to go this high.

[Felix M.]

Thanks for your advice All Science (and keep doing your yt content )
Since it's very common in Germany to have a 16A fuse on each 400V phase, I want it to be limited to 10kW peak power.
The datasheet of my IGBTs calls for 300A collector current and a high short curcuit capability with self limiting characteristics at 6 x Ic.
With good ZCS I think it might be possible to "savely" push the current up to the 1000A mark. I will try it out for sure but it will take some time until I have the whole build finished.

[Mads Barnkob]

There is only answer, you calculate it. I got an example of how to do so here: https://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/igbts/ At the bottom of the page, there is also a table of previous proved uses of different IGBTs. SKM200 has been used between 450-750A.