Superconducting wires conducting dc incur very low losses
Superconductors used for AC conducting incur hysteresis and eddy current losses in that require increased cooling capacity at a system level and limit the AC frequency.
NASA has made significant progress developing and characterizing new, higher frequency (>200Hz), AC superconductors that could be used in electrical machines
Through a series of NASA SBIR contracts, fabrication techniques for MgB2-based conductors were improved, and small filament sizes as low as 10 μm were demonstrated.
NASA has also sponsored the development of an experimental capability to calorimetrically measure ac losses and stability properties of superconductors at temperatures as low as 15 K under simultaneous ac transport current and rotating and pulsating magnetic fields as would occur in rotating machine stators