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Heat sink temperatures
By billf, Section Homebrewed Electricity Posted on Fri May 09, 2003 at 09:07:04 PM MST
While having some sustained 30-35 mph winds

this evening I noted the heat sink to be almost too hot to touch. Output was 60 to 70 amps for at least an hour. My VOM has a digital temp selection and so by touching the probe to the various areas of the ac/dc box here is what I got: Rectifier: 245 F Bottom of heat sink 177 F Top of heat sink 140 F Now the rectifier has an max operating range up to 125C/257F so obviously this will impact the life span. So this will mean that a fan will be added to blow air across the rectifier and heat sink. Some sort of temp. switch will control it. Also the tail assembly will be lightened so the mill will furl a bit sooner. There is something to be said for mounting the rectifiers and heat sinks on the mill for cooling even though I like to keep as much on the ground as possible.

Heat sink temperatures | 3 comments (3 topical)

Hot rectifiers! (none / 0) (#1)
by DanB on Sat May 10, 2003 at 02:08:22 PM MST

Bill - are you running 12 Volts?

this is another good reason to run higher voltage! (I run 12 volts and the losses in the rectifiers are over 10% - which all turns into heat)

When we put up Wards brake disk machine, we had 3 40 amp rectifiers in parallel (120 amp rating) and bolted them all to about 1/2 the heat sink that you've got going. We were having sustained 30-40 mph winds at that time with gusts up to 60 or more(and his windmill doesn't furl). In no time the heat sink got too hot to touch, and the rectifiers lasted less than 10 min.

I've learned since then, the rectifiers should be extremely over-rated and the heat sinks should be huge! I've had enough rectifiers fail, I'm a bit afraid to put them on top of the tower, although I'd agree that would help with cooling.

We fixed Wards by using 6 40 amp rectifiers in parallel, and the heat sink is a big one from an old car audio power amplifier, about 10" wide and 12" long with lots of fins... It's not been a problem since, they hardly warm up at all.

heat sink grease (none / 0) (#2)
by ADMIN on Tue May 13, 2003 at 11:39:57 AM MST

And use heat sink grease...you can buy it at Radioshack. It helps a bunch for heat transfer. There are also plastic pads that do the same thing now -- they are less messy but more expensive.

DANF

[ Parent ]

About that Radio Shack grease (none / 0) (#3)
by Bach On on Thu Jun 05, 2003 at 09:04:46 PM MST

I used to dabble in what is called overclocking with my computer. It's basically running the central processing unit at a higher speed than it is rated for. The trade-off is that it tends to run a bit hotter. There are forums (almost as good as this one) where folks swap ideas and notes on how to cool down the CPU to reach higher speeds.

The Radio Shack heatsink grease was one that most of the folks on those groups said was one of the poorest at reducing the heat build-up. Most favored a product called Artic Silver. As its name implies, it had silver particles embedded in the grease to help disapate the heat. I tried some and can tell you that it cooled much better. The cost is about double that of the Radio Shack paste, but it is worth the difference.

Those plastic thermal pads are even worse than the Radio Shack pads.

My 2 cents worth - and worth all it cost you.

Bach On

- - I'm not superman, but I am very dense! -
[ Parent ]

Heat sink temperatures | 3 comments (3 topical)

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