Special Rotor: The key element of the 5-MW superconductor motor [shown in artist's cutaway], designed and developed by American Superconductor, is the superconducting rotor that produces extremely strong magnetic fields. To keep the rotor in a superconducting state, an adjacent cryocooler [not shown] circulates helium gas cold enough to keep the rotor at about 32 K. The copper stator coils also require cooling, but oil keeps them at more normal operating temperatures.