thermal resistance, dummy loads

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From	Christopher Howard <christopher@librehacker.com>
Newsgroups	sci.electronics.design
Subject	thermal resistance, dummy loads
Date	Thu, 23 Apr 2026 13:33:01 -0800
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Hi, I'm wondering what could be used as a dummy load for testing low
voltage, high wattage DC power supplies. E.g., I have a 12V 500W DC PS I
wanted to test under heavy load. I see 50 ohm dummy loads for ham stuff
are easy to get, but that would be too high a resistance for something
like 12V.

I see 1 ohm, 200W resistors are easy to find, like the HS200 1R J. But
in the fine print you've got to provide a correctly rated heatsink. When
I did the calculations for maximum total thermal resistance, assuming
200W power dissipation, and some non-conservative values of standard
room temp and a max junction temp of 200 ℃, I'm looking at less than 1 ℃
/ W total thermal resistance, and the heatsink ends up being five times
the cost of the resistor.

So I'm wondering what is the practical way forward. Like, put the
resistor in mineral oil? Or get some nichrome...?

-- 
Christopher Howard

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thermal resistance, dummy loads Christopher Howard <christopher@librehacker.com> - 2026-04-23 13:33 -0800
  Re: thermal resistance, dummy loads joegwinn@comcast.net - 2026-04-23 18:32 -0400
    Re: thermal resistance, dummy loads Christopher Howard <christopher@librehacker.com> - 2026-04-23 15:15 -0800
      Re: thermal resistance, dummy loads joegwinn@comcast.net - 2026-04-24 18:12 -0400
  Re: thermal resistance, dummy loads john larkin <jl@glen--canyon.com> - 2026-04-23 17:18 -0700
  Re: thermal resistance, dummy loads Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-04-24 00:42 +0000
  Re: thermal resistance, dummy loads "Edward Rawde" <invalid@invalid.invalid> - 2026-04-23 20:44 -0400
    Re: thermal resistance, dummy loads Jeff Layman <Jeff@invalid.invalid> - 2026-04-24 08:46 +0100
  Re: thermal resistance, dummy loads Jan Panteltje <alien@comet.invalid> - 2026-04-24 07:32 +0000
  Re: thermal resistance, dummy loads liz@poppyrecords.invalid.invalid (Liz Tuddenham) - 2026-04-24 09:28 +0100
  Re: thermal resistance, dummy loads legg <legg@nospam.magma.ca> - 2026-04-24 11:18 -0400
  Re: thermal resistance, dummy loads Simon Simple <nothanks@nottoday.co.uk> - 2026-04-27 23:34 +0100
    Re: thermal resistance, dummy loads Jan Panteltje <alien@comet.invalid> - 2026-04-28 06:44 +0000

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