Electronic – Controlling high current (1000A) with MOSFETs


I am currently designing a capacitive discharge spot welder and am running into the issue of switching.

I plan to use a few super capacitors in series to discharge around 1000A in a very short period of time (most likely less than 100 milliseconds). I plan on charging the capacitors to around 10V.

So I essentially need a device capable of delivering a short pulse of very high current. I do not want to dump the entire charge of the capacitor in one go, so SCRs are not a solution to my issue. I have been looking at MOSFETs, and this one catches my eye: http://www.mouser.com/ds/2/205/DS100728A(IXTN660N04T4)-1022876.pdf

However, I am unsure of how exactly to interpret the datasheet. Is the MOSFET capable of driving 1800A as its pulsed drain current states? Or is it limited to 660A (or even 220A), forcing me to wire a few of these in parallel? Or will one of these MOSFETS be fine? According to my preliminary calculations, a lone MOSFET connected directly to the capacitors without any other resistance would be dissipating around 900W, which seems to be within the range of the data sheet.

So essentially, am I interpreting the data sheet correctly, or do I need to order a few of these MOSFETs (and if so, how many would you guess?)

Best Answer

Look at page 4, fig.12, graph of safe operating area. That is exactly what you need.

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You are talking about single pulse, right? You didn't mention any repetition or timing at all. If you open mosfet hard, say Rdson is 0.85mOhms. In case of 1000A the Vds will be less than 1V, so you have to look at the left side of graph.
There is no line for 100ms pulse, so you have to interpolate between DC and 10ms pulse. The safe current is much lower than 1000A. It is like 400A. And it is the maximum.