Hello,

I am in the process of designing some motor controllers  and am thinking of
removing (or at least reducing the size of) the heatsinks I am using by
placing a fan over the MOSFETs.  I have some datasheets from Wakefield
Engineering the nicely show the Thermal Resistance from Sink to Ambient for
different LFM rates.  From this I have been able to determine I could get
away with a very small  heatsink.  What I can not determine is if I need a
heatsink at all.  Does anyone know where I can find a Thermal Resistance
from Sink to Ambient for different LFM rates for a TO-220AB casing (i.e.
with no heatsink)?  Does it sound reasonable that with an ~500LFM fan I
could put 30A through an h-bridge that consisted of 2 IRF1404 MOSFETs (4mOhm
on resistance) in parallel for each leg?

Thanks,
Donovan

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