Setting over current protection for my drsstc

[octopus1]

Hello all,

I have been thinking way to hard about this and I feel like it should be simple. I should set the over current protection to the max current rating of my igbt. Or am I over looking something simple.

Thanks in advance! 

[Mads Barnkob]

Hello all,

I have been thinking way to hard about this and I feel like it should be simple. I should set the over current protection to the max current rating of my igbt. Or am I over looking something simple.

Thanks in advance! 

You should set it to something you dare push your IGBTs to or it could also be used to limit the voltage across the MMC. Just two sides of the same case.

If you are looking for proven numbers, there is a list of IGBT peak currents in a Tesla coil / DRSSTC here

If you are looking to do the math and calculate the maximum current for your IGBT in a Tesla coil / DRSSTC, scroll down to Fmax2 calculations here

Calculating the voltage across the MMC can be done with the MMC calculator or if you want the full theory behind it, then MMC design for Tesla coil / DRSSTC is where you want to go

[octopus1]

Thanks! So I got that I need a current limit of 800a. I’m using a cm300dy-12nf brick, a .235uf 8kv mmc, and 8 turns of 1/4” copper tube for the primary. Let me know if that sounds way to high, thanks for all the help I wouldn’t be able to do this project with your website and the good people on this forum.

[Hydron]

800A sounds reasonable but only IF your resonant frequency is over ~70kHz. If it is lower than that then the MMC voltage rating is too low (and I'd try to give a bit more margin than peak voltage = DC voltage rating). The IGBT should be OK at 800A or a little higher.

[octopus1]

Oh good! My resonant frequency is around 90khz so it should be fine then, again thanks for all your guys help