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0 pointslazide4mo ago0 comments

It’s great anywhere you want more power but are limited by space and/or weight for performance reasons. Aerospace, e-bikes, electric race vehicles, electric motorcycles.

But yeah, EVs seem weird except for racing reasons perhaps.

What I can’t figure out is how they dissipate the heat - double digits kw per kg is crazy.

0 comments

benplumley4mo ago

    The YASA axial flux motors benefit from much shorter windings and direct oil cooling which gives an unparalleled performance proposition.  
      
    A 200kW peak-power radial motor, run continuously, might typically give 50% of peak power between 80 and 100kW, as a result of thermal limitations. In contrast, a 200kW YASA motor runs continuously at 150kW thanks to the improved high-thermal-contact cooling that oil offers.

From https://yasa.com/technology/

Tostino4mo ago

The first step to dealing with heat at high kw, is to not generate the heat you have to dissipate in the first place. Which means chasing smaller and smaller efficiency gains, because that reduces heat generated.

The more of the energy going into moving the vehicle, the less heat the motor has to handle.

lazideOP4mo ago

Sure, but at 50kw/kg at 99% efficiency is still 500w/kg, which is cray cray. Like ‘glowing red hot shortly’ type of crazy with just passive cooling.

And there is no way this is 99% efficient.

So my question still applies. Even 98% is 1kw/kg, or 1kj/sec. or around 3C rise per second assuming the mass is 100% nice clean copper (it isn’t). Everything else will be worse.

Not even counting increasing losses with temperature, it will be a molten puddle pretty quick at that rate without some major active cooling.

I_dream_of_Geni4mo ago

I was waiting to see in the comments EXACTLY this question: There is no way to dump this heat. 1000hp? Yeah, maybe for a few seconds, even with oil coolant pumping through there. Then how to dump the heat from the oil. And further thinking, if they ever get this to be a hub motor, how in the world are they going to pump coolant through 2-4 hub motors and then to a radiator that can dump that rate of heat rise, especially since oil is a lousy coolant (relatively speaking).

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ajross4mo ago

Again, no, because the motor needs to be powered and the battery is vastly larger than the motor already in any of those applications. Even in RC planes, which fly for 5-6 minutes at a time, the battery is 5x or more the weight of the motor, wiring and controller logic.

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