What limits superconducting machine power density?

[Stormer]

Hi. There has been a fair amount of research into electric generators and motors with superconductive coils. If traditional iron cores is used that obviously limits the power density because of the iron cores magnetic saturation point. But for coreless/ironless designs i don't understand what limits the power density? From what i have read they are talking about 20 kW/kg with current designs and maybe up to 30-50 kW/kg in the future. But can you not just pump as much current as you want into a superconducting wire without generating any heat or resistivity and therefore have almost as big of a power density as you want (as long as it can mechanically handle the torque and speed)? What limits the current able to be passed trough a superconducting wire?

 

[Vanadium 50]

But can you not just pump as much current as you want into a superconducting wire

No.

Eventually it goes normal.

 

[OCR]

Eventually it goes normal.

Yes, and. . . normally it's not a very nice "normal" normal. . .

.

 

[Baluncore]

What limits the current able to be passed trough a superconducting wire?

There is a maximum current limit determined by the magnetic flux in the superconductor.
The Meissner state breaks down when the applied magnetic field is too strong.
https://en.wikipedia.org/wiki/Superconductivity#Meissner_effect