>
>>Let's say that I have a source of about 800-1000 watts (two dual IGBTs
>>inverting 200 amps). They should run relatively cool, to stay safe say
>>under 80 C. I have a heatsink that is about 6x13 inches and weighs
>>perhaps 12 lbs. I am cooling it with a fan mounted right next to the
>>ribs, pushing air along them, the fan is about 20 watts. Ambient temp
>>could be quite hot, say 40 C (inside welding machine). Would you say
>>that this amount of cooling should be enough? I will have a overheat
>>switch mounted on the sink, so, hopefully, worst case would be a
>>inconvenience of having to stop welding, but I would like to have some
>>idea of adequacy of this setup.
>>
>>i
>
> I did a big ugly 800-watt CAMAC power supply, with a heatsink about
> that size. A single 120 CFM fan was ducted (custom vacuum-formed
> plastic thing) to blow all its air through the fins, not *near* or
> *around* the fins as fans are wont to do.
>
> I got a tad over 0.04 K/W, but that was with the heat load fairly
> uniformly distributed over the heatsink baseplate. Concentrated heat
> loads would be worse because of lateral (spreading) thermal
> resistance.
>
> If you don't duct the air, impingement is almost as good: orient the
> plane of the fan parallel to the sink and blast the air directly into
> the fins at short range. Tweak distance maybe.
>
> Your numbers sound tough to do, but not impossible.
Thanks. This assembly will be mounted horizontally, very close (like 1 cm) above the bottom of my welder. Or even directly on the bottom.
Here it is, with comments:
formatting link
The main power units are not yet mounted. Wanted to see what you think. There is the snubber circut there already, however.
Thank you.
i