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

Hi,
in a month I want to start building my first middle sized DRSSTC. I want to describe my plan here. I will use UD2.7C, I have already built it and tested it.

I am attaching screen of JAVA TC. Is there anything that should be different? I will make the primary coil about 8 turns so I can fine tune it later.

My main question is about bridge construction. I am attaching photo of my layout for the bridge - it´s davekni´s design. I hope it should be fine, maybe I will add some solder to it to make it thicker. Hopefully it will be just fine. I want to use that tranzistors - HGTG30N60A4D. They are tested by this guy up to 430 A peak in bridge configuration - https://www.vn-experimenty.eu/teslov-transformator/drsstc/drsstc-3.html (hopefully the google translation will be good enough, otherwise I will try to describe it, I am from Czech Republic and he is from Slovakia). Firstly I want to build bridge configuration and to try it to let´s say max 370 A peak. But then I want to build double bridge with 8 transistors in total. I don´t expect double the current, but it´s possible that double bridge could handle 700A as example? Unfortunately I can´t afford buying IGBT bricks.

The next thing I'm not sure about is cooling. I am attaching photo of my heatsink, dimensison are written on it. I have two of them. Each heatsink will have 2 or maybe later 4 transistors. I am not sure if it is good enough even if I add cooling fan to them. I'm afraid the transistors will overheat.

The last question is about GDT. I want to use both outputs of my UD2.7C, so 2 GDTs. For single bridge it´s clear. I will use 2 GDTs each with 2 secondary coils. But I wonder if I could use the same GDTs for double bridge (use every secondary coil for 2 transistors in parallel) or I would have to rewind them so each transistor has its own secondary coil, so 2 GDTs each with 4 secondary coils.

Thank you very much for any advice or suggestion 

Hello guys,
I am almost beginner.
I built a medium size SSTC, PLL controlled with 4046. I´m attaching a schematic. Today I tried to set the phase close to zero current switching, but I have a problem. When the oscilloscope shows the phase setting close to ZCS, my IGBTs get really hot. When I tried to set it so that the transistors warmed up as little as possible and then I measured on an oscilloscope I got a weird result. On the oscilloscope, it looks like if it really was like that, it would mean an immediate explosion, it looks like its switching on the peaks. So I wonder where the mistake is. I use very basic oscilloscope, so I think that this is the problem. I am measuring the current with suitable torroid and about 30 turns and 4,7 Ohm resistor. Is it possible that the oscilloscope is slow and does not measure it correctly? Thank you very much for your help.