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From: Lasse Langwadt <llc@fonz.dk>
Newsgroups: sci.electronics.design
Subject: Re: dumping a lot of heat
Date: Fri, 6 Dec 2024 17:56:05 +0100
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On 12/4/24 22:55, Joe Gwinn wrote:
> 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


https://www.reddit.com/r/CNC/comments/1es1d01/someone_didnt_believe_me_when_i_said_that_our/