TO220 Heatsink

Discussion in 'General Electronics Chat' started by selfbg, Feb 4, 2012.

  1. selfbg

    Thread Starter Member

    Jun 11, 2010
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    I cant find anywhere heat sink for TO220 with the spec:
    The total power is ~70W.
    So "theta" sink-to-ambient = 0,92°C/W.

    It doesn't matter natural or forced cooling.

    Thanks in advance. :)
     
  2. #12

    Expert

    Nov 30, 2010
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    aavidthermalloy.com has heat sink calculators and air velocity calculators. That might lead you to a product that you can buy.
     
  3. selfbg

    Thread Starter Member

    Jun 11, 2010
    23
    0
    I checked the site, but still can't find suitable heat sink.
     
  4. #12

    Expert

    Nov 30, 2010
    16,339
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    Part # 530002B02500G is the largest TO-220 sink listed at Aavid. It's free air theta is 2.6

    The only cure for that is air velocity. Clicking on that part number brings you to a page which has a graph of velocity vs. theta. www.avidthermallow.com/products/standard/53002b02500g

    The answer is 1000 feet per minute.
     
  5. crutschow

    Expert

    Mar 14, 2008
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    For that much power a heatsink with an integrated fan would likely be best. Perhaps you can adapt a CPU cooler for PC to your needs such as one of these.
     
  6. bertus

    Administrator

    Apr 5, 2008
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  7. #12

    Expert

    Nov 30, 2010
    16,339
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    There is also the option of using a different (bigger) package. A TO-3 plus proper heat sink and fan might be smaller than a TO-220 with proper heat sink and fan.
     
  8. Wendy

    Moderator

    Mar 24, 2008
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    I like the CPU heatsink/fan idea myself. You will have to drill/tap the holes yourself.
     
  9. jimkeith

    Active Member

    Oct 26, 2011
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    Last edited: Feb 4, 2012
  10. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    To get 0.9C/W you need an extruded heatsink, very large and heavy. probably about 12" wide, 4" high.

    BTW: if power dissipation forces the use of a heatsink < 1C/W, TO-220 devices are a poor choice. They have a theta of about 4C/W from junction to case. TO-3 is a much better choice.
     
  11. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
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    CORRECT. Thermal resistances add in series. The 4C/W junction-case of the TO-220 is MUCH larger than 0.9C/W. Going to the TO-3 which is <1C/W junction-case saves most of the total thermal resistance.
     
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