Production and Test of a REBCO Superconducting Synchronous Motor

We designed and fabricated a 7.5 kW–360 rpm synchronous motor with a superconducting rotor. The rotor was 6-pole type and has no iron core. The armature winding was wound with copper wires. 6 pieces of racetrack-shaped field coils were wound with 5 mm wide $\hbox{RE}_{1}\hbox{Ba}_{2}\hbox{Cu}_{3}\hbox{O}_{7-\delta}$ (REBCO, RE:Rare Earth) superconducting tapes produced by an ion beam assisted deposition method and a pulsed laser deposition method. The total length of REBCO tape was 400 m per a field coil. We confirmed the good transport properties of the respective field coils up to 80 A at 40 to 50 K before and also after the assembly to a motor. The maximum magnetic field in the field coils was 0.67 T. The superconducting rotor was cooled down to around 40 K by forced-flowed helium gas and the completed motor was tested in a similar way to conventional motors. As a result of a load test, the designed operation of 7.5 kW at 360 rpm was verified for the rated field current of 60 A. Even when the field current was increased up to 70 A at 40 K, the temperature at each part of the superconducting rotor was held constant and the quite stable operation up to 11 kW at 360 rpm was also achieved.