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I am trying to apply 1 kW of heat to an area of 10x10 mm and I am considering using a panel mounted film resistor.

One that meets my power requirements doesn't exist so I am wondering if I can go above the normal power rating if I sufficiently cool the resistor.

Could I use a lower powered one as long as the heat was adequately removed?

(I should say the point of this is I am developing a heat sink for high powered electronics and the temperature of the resistor wouldn't go above the normal recommended temperature)

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    \$\begingroup\$ is that heat flow not hotter than surface of the sun? \$\endgroup\$
    – analogsystemsrf
    Commented Sep 10, 2019 at 14:52
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    \$\begingroup\$ sun is about 0.8million mile diameter; at earth, that sphere is 93Million miles radii, or 180Million mile diameter; heat flux onto our earth (thru our atmosphere) is 1,000 watts/square meter; scaling that back to surface of sun, using [180Million/0.8Million]^2, is about 1,000watts / 60,000th of meter or about 4millimeter by 4millimeter. Thus you want HOTTER than the sun, even before accounting for atmospheric absorption. \$\endgroup\$
    – analogsystemsrf
    Commented Sep 10, 2019 at 14:59
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    \$\begingroup\$ @AndrewAnderson We'll need the info on how to connect to your C: drive to be able to read that ;) \$\endgroup\$
    – Andrew Morton
    Commented Sep 10, 2019 at 15:05
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    \$\begingroup\$ Well @analogsystemsrf, maybe adequately heatsinking the Sun might do the trick... :P \$\endgroup\$
    – Enric Blanco
    Commented Sep 10, 2019 at 15:06
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    \$\begingroup\$ @AndrewMorton haha I was viewing it in my browser and didn't even notice. ieeexplore.ieee.org/document/1665571 \$\endgroup\$
    – Andrew Anderson
    Commented Sep 10, 2019 at 15:10

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For a 100’C rise per 1kW input you would need a CPU style heat sink with 0.1’C/W thermal resistance with size and force air of a super cooler heatsink. These are typical much larger(10x) than your allocated area and have >10m/s air velocity over a large number of fins.

  • water cooling would be necessary to reduce the area to 1 cm^2 with a very efficient heat exchanger.
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  • \$\begingroup\$ Thanks. The purpose of my project is to develop a new kind of cooling device for high powered electronics and I can't think of any reason why you couldn't superrate the resistor as long as it was kept cool \$\endgroup\$
    – Andrew Anderson
    Commented Sep 10, 2019 at 15:21
  • \$\begingroup\$ Ceramics may operate at 150’C and some higher. But do the math on thermal resistance, your miserly area needs a super cooler like a copper sponge heat water cooler to achieve <=100’C rise at max ambient (TBD) \$\endgroup\$
    – D.A.S.
    Commented Sep 10, 2019 at 15:33
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In general, yes you can push a resistor beyond its ratings just as you would a transistor. We have cooled inductors and capacitors as well. However, the devil is in the details.

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  • \$\begingroup\$ Thanks. This is what I generally wanted to know. I just don't know if there was any other issues I would encounter other than heat generation \$\endgroup\$
    – Andrew Anderson
    Commented Sep 10, 2019 at 15:32
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In general, no you cannot operate a device beyond its specified maximum operating conditions without risking failure.

Remember that the power rating of a resistor is not the only limitation. There are also limits on the maximum current and the maximum voltage. If you are attempting to dissipate 1kW through a resistor then either your voltage or current are probably very high.

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  • \$\begingroup\$ I am aware of maximum voltage being an issue because of shorting and maximum power due to heat but if that is properly dissipated so the resistor stays in a safe operating temperature I can't see why it wouldn't work. Are there other issues I'm not aware of? \$\endgroup\$
    – Andrew Anderson
    Commented Sep 10, 2019 at 15:18
  • \$\begingroup\$ Yes, maximum current. I am also doubtful that you can really keep the entire body of the resistor within its specified operating temperature range at 1kW. \$\endgroup\$
    – Elliot Alderson
    Commented Sep 10, 2019 at 15:24
  • \$\begingroup\$ Can you explain what would happen if I exceeded the maximum current other than excessive heat? Right now there isn't anything in the world that could keep it within range. That's what my research is aiming to do :) \$\endgroup\$
    – Andrew Anderson
    Commented Sep 10, 2019 at 15:29
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    \$\begingroup\$ For thin film conductors with very high current density you may see electromigration, where the electron flux literally moves the metal atoms around. The current density is higher where the metallization is thinner, so any non-uniformity in the metal will exacerbate and accelerate the problem. And remember that you must keep the entire structure below the maximum temperature...you can't allow localized heating inside the structure or you risk normal fusing of the conductors. You really haven't provided anywhere near enough information to give you a good answer. \$\endgroup\$
    – Elliot Alderson
    Commented Sep 10, 2019 at 16:33

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