Liquid Nitrogen

[motomoto]

I have been researching Liquid Nitrogen and how it sucks heat when evaporated. I want to use it to cool motors
and power transistors in controllers. It might eliminate controllers blowing and motors could run at 10 times their
normal power rating.

Youtube is strewn with computer dudes chilling their CPUs with liquid nitrogen to overclock their processor speeds,
why not chill our power transistors so they can 'overclock' and not burn up. Copper resistance is inversely proportional
to temperature. Motors might run sweet at -30 C and transistors might run forever at -200 C.

Just a thought.

 

[bigmoose]

Before you go too far... find your source of LN2 and the cost. Then figure in the cost and weight associated with storing and carrying it on your bike. Calculate the amount of LN2 required to remove the BTU's (watts) that you consider waste heat from the controller, figure the cost. Then look at the specification sheets for semiconductors and look at the minimum use temperature. Finally look into why NASA heats spacecraft electronic bays in deep space and why cold is their most significant design challenge for electronics in deep space.

That said, cooling ultrapure motor copper with LN2 gets you most of the way towards a superconductor. I have posted links to research papers on this concept in the past. You can likely find them with a search.

 

[Njay]

Not with LN2, but I have thought in the past to use a can of "freeze" (the ones used in electronics to cool chips) to provide *momentary* cooling boost for motor/controller. Have no idea if it could be advantageous, considering duration and cost of a can.

 

[amberwolf]

And also keep in mind that extreme cold (especially if combined with cycling to warmer/hotter temps) is likely to damage solder joints (or any bimetallic connection, whether electrical or mechanical), and in multilayer boards may also break the vias thru the layers.

 

[Drunkskunk]

I winder what the eddy currents in the stator laminations would do at superconductor temps?

LN2 is expensive. People have knocked around the idea of NO2 for motor cooling, as it's much cheaper and safer to work with. (Imagine skidding out in a corner, breaking the LN2 dewar, and then landing face first in a pool of LN2. Or worse, a hose leak blowing LN2 all over your balls. You saw Terminator 2, right? I seriously don't want shattered balls. )

But the usual conclusion is the cost is still prohibitive, and the results wouldn't be worth the effort. Instead a simple liquid cooling system would work better. I know Doc and a few others are working on Liquid cooled motors. Not sure if anyone has a finished motor yet.

 

[dnmun]

you have to remember too that the material properties change with the temperature and the semiconductors would not be semiconductors at such a low temperature.