Am I right with the following:
The datasheet shows Maximum permissible Power Dissipation of 330W.
The power dissipation for a MOSFET with RDS on specified as 0.0055 (5.5milliohms) at 30A is (30 x 30) * 0.0055 = 3.43W
As 3.43W is below 330W this does not require a heat sink?
Seems too simple and given the expected current - I would think it needs one - but the above says not so much.
I'm working on the theory that I'll oversize the MOSFET and simply use a 169A MOSFET. As I am switching it, and the current will always be below 169A - there won't be an issue in sizing.
The datasheet is here if it helps:
http://www.jaycar.com.au/productView.asp?ID=ZT2468
I'm looking for confirmation that using a 30A rated MOSFET such as IRF540N would not be better (I don't think it is because of greater RDSon) - but is there any other reason you'd not want to use a higher current rated MOSFET?
One for each fan.