Rotating windings?

Username1

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I have an interest in coreless axial hub motors which are known to not tolerate heat well because of having no iron. I was thinking of how to improve this, and was wondering if there's a way to have the windings rotate with the wheel. That would mean they can directly transfer their heat to the case with solid contact.

I guess this could be done with brushes, even though they have downsides. Are there any other methods that could achieve this, maybe something wireless? And wouldn't this be worth it for the continuous power density that would be possible? Just an idea/question.
 
brushes are pretty much the only way to do it in a small space at any appreciable power density.

Then you have the heat from brush arcing, and the loss of efficiency from that, and the wear on the brushes and commutator segments or rings (depending on which type of motor you are using) (which means replacing those parts periodically; the higher the currents and voltage the more the wear and heat)

There is also some fairly intense RF generated by the arcing; the motor controller may need to deal with this to protect the FETs and/or drive circuitry from random noise events. Depends on the level of the RF and noise, whether it's a problem or not.


You'd probably be better off going with oil cooling, forced-air cooling, ferrofluid and heatsinks, or some combination of these.

See the long thread about "definitive tests on heat/cooling hub motors" for LOTS of info about this.
 
What about using bearings to send electricity to the windings, would it be possible?
 
Passing an electric current through a bearing is normally a good way to destroy it (machines with improper grounding can do this), but it will be so lightly loaded I don't know if the damage will manifest in a time scale that is significant.
 
If the bearings could do the job, maybe you could do a design with 2 electromagnetic rotors outside and a permanent magnet stator inside, and make each rotor 1 phase for a 2 phase motor. That way you won't need electronics inside the motor to direct the electricity after it passes the bearing. Hopefully that makes sense.

I saw this about bearings. It seems like sparks create really high temperatures that melt little holes in the bearing, so this article explains how conductive lubricants are being developed to mitigate this http://www.car-engineer.com/conductive-lubricants-bearings/
 
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