Parallel arrangement of large MOSFET transistors peak current through 3000A?

[carpenter]

I am considering something like a capacitor spot welder. The key point is a large transistor block that switches a large current for a given short time.
The original idea was to use parallel 2pcs IXTN660N04T4 (40V, 660A 850 uOhm) directly on the copper rail. Unfortunately, I currently buy this MOSFET for about $35/piece.
IRL40SC228 (40V, 360A, 500 Ohm) I can buy for $1/each, The transistor has half the gate capacity, is faster and is mainly limited by the D2PAK-7Pin case.
Driving. 5pcs MIC4421A 9A Peak Low-Side MOSFET Drivers. 2X20nF gate this chargo on 15V approximately for 100ns.
I'd be interested in your opinion, it seems like a good idea that $10 brings more music than $70

 

[KlausST]

Hi,

for a given short time

what does this mean?

(40V, 360A, 500 Ohm)

seems not to be correct

2X20nF gate this chargo on 15V approximately for 100ns.

Did you forget about Miller charge? ... you need to know the switching voltage..


Klaus

 

[carpenter]

OK let me clarify a bit.
First of all, as can be seen from the referenced datasheet, RdsON is 500 uOhm not 500 Ohm
How do things like that work.
For example, I will use 4 capacitors 3V, 3000F, 3Wh, 260 uOhm, in series (12V, 750F) as a source.
As a conductor between the source and the transistors, let's assume a copper strip 20x5x500 mm with a resistance of 10 uOhm.

Regulation of the power supplied to the welded point is possible by the voltage on the capacitor, but mainly by the length of the welding pulse.
The length of the pulse, let's say that the setup is from hundreds of us to hundreds of ms.
I measured the peak discharge current of one capacitor and I measured just over 2500A

 

[dick_freebird]

My concern would mostly be about current sharing and
at such low internal Ron, PCB layout becomes a big
deal. So too may be any mismatch between the FETs.
A task before you is to figure out how much / badly
can still be tolerated (not easy to find the low level data
you'd need) and/or to segment the FET such that you
could stand one that's "phoning it in" or prevent one
that's "overly ambitious" from failing alone (maybe then
causing the next...).

At 3000A you're not going to be able to put any explicit
ballasting I reckon.