Re: dumping a lot of heat

On Wed, 04 Dec 2024 13:29:03 -0800, john larkin <jl@glen--canyon.com>
wrote:
 

I'm thinking about building a biggish rackmount dummy load box. It
would simulate series resistance and inductance. Part of the problem
is that it will need to dump a lot of heat.
>
We are using copper CPU coolers on PC boards, which are great up to a
couple of hundred watts, but I'd like to do a kilowatt or two.
>
https://highlandtechnology.com/Product/P945
>
It would take a heap of expensive extruded heat sinks and fans to get
rid of a kilowatt. At 1 K/W, a pretty good heat sink, that's 1000 degC
temp rise.
>
A small hair dryer can dump a kilowatt. So some sort of red-hot
nichrome coils and a vicious fan might work.
>
I'd prefer to not use water.
>
I wonder if there is some sort of runs-red-hot power resistor.

 Yes.  A toaster element: Nichrome wire woven onto a mica card in a
perforated metal box.
 Already packaged, one can get ballast resistors for high-power VFDs
used to power machine tools.  The ballast resistor absorbs the energy
stored in a large chuck spinning fast, when it's time to come to a
stop quickly without over-voltage tripping the VFD.
 .<https://www.automationdirect.com/adc/shopping/catalog/drives_-a-_soft_starters/ac_variable_frequency_drives_(vfd)/braking_units_-a-_resistors/br-n1-800w18p0>
 Joe Gwinn