Advise on heat sink

pmchoong · 6th October 2008, 04:57 PM

Hi everybody. I have a question. The heat sink I can find here is 150 (h) x 100 (w) x 25mm (d). I intend to mount the mosfet onto the heat sink. Please see attached images. Will this be enough? These heat sink are from China and o specs on them. Please help.

AndrewT · 6th October 2008, 05:04 PM

how much heat do you need to dissipate?
What temperature is acceptable at the FET case?

pmchoong · 6th October 2008, 05:10 PM

Thanks for reply. I would like to have the case at 55c. This is A5 mono.

guitvinny · 6th October 2008, 05:16 PM

Maybe you can try to mount a resistor and plot the temp rise at various point with some thermometers.

jacco vermeulen · 6th October 2008, 05:19 PM

Think 1.5C/W for a single of those 150mm/6" heatsinks.
So 2 rows of 4 heatsinks should be able to handle the 150W.

It's not such a bad idea to use those sleek heatsinks, if you don't mind the 40cm/16" depth of the amp.

pmchoong · 6th October 2008, 05:23 PM

I haven't got the heat sink yet. They are expensive and I can't afford to experiment with trial and error. These are the medium size heat sink, the bigger size ones are way too large and the smaller ones is a bit too thin.

jacco vermeulen · 6th October 2008, 05:27 PM

Then estimate the C/W number with a thermal resistance calculator.

pmchoong · 6th October 2008, 05:30 PM

Thanks, I do not mind the 400mm depth at all. So, these heat sink should be able to handle the heat. Thanks for the help. I will go ahead with the plan.

Magura · 6th October 2008, 05:36 PM

Quote:

Originally posted by pmchoong
So, these heat sink should be able to handle the heat.

NO! What people have told you, is based on guessing. To you it should translate into something like:

"Those heatsinks are worth checking out a bit closer, and do some calculations."

As Jaccolina stated above, there are online dissipation calculators around, and if sucha a calculation tells you that the heatsink is big enough, well, then it's a bit closer to a green light.

Magura

pmchoong · 6th October 2008, 05:46 PM

Quote:

Originally posted by Magura

As Jaccolina stated above, there are online dissipation calculators around, and if sucha a calculation tells you that the heatsink is big enough, well, then it's a bit closer to a green light.

Magura

Dissipation calculators? Please pardon my stupidity, I do not know how to use these calculators. The maths involved is too complex.

6th October 2008, 05:19 PM	#5
jacco vermeulen diyAudio Member Join Date: Oct 2004 Location: At the sea front, Rotterdam or Curaçao	Think 1.5C/W for a single of those 150mm/6" heatsinks. So 2 rows of 4 heatsinks should be able to handle the 150W. It's not such a bad idea to use those sleek heatsinks, if you don't mind the 40cm/16" depth of the amp. __________________ Not so much,.......if it says "ZM" in the corner.

6th October 2008, 05:27 PM	#7
jacco vermeulen diyAudio Member Join Date: Oct 2004 Location: At the sea front, Rotterdam or Curaçao	Then estimate the C/W number with a thermal resistance calculator. __________________ Not so much,.......if it says "ZM" in the corner.

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6th October 2008, 05:04 PM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	how much heat do you need to dissipate? What temperature is acceptable at the FET case?

6th October 2008, 05:16 PM	#4
guitvinny diyAudio Member Join Date: Nov 2005 Location: Québec	Maybe you can try to mount a resistor and plot the temp rise at various point with some thermometers.

6th October 2008, 05:23 PM	#6
pmchoong diyAudio Member Join Date: Jan 2008 Location: Kuala Lumpur	I haven't got the heat sink yet. They are expensive and I can't afford to experiment with trial and error. These are the medium size heat sink, the bigger size ones are way too large and the smaller ones is a bit too thin.

6th October 2008, 05:30 PM	#8
pmchoong diyAudio Member Join Date: Jan 2008 Location: Kuala Lumpur	Thanks, I do not mind the 400mm depth at all. So, these heat sink should be able to handle the heat. Thanks for the help. I will go ahead with the plan.