Rotation Test of a Superconducting Bulk Rotor Shielded With Superconducting Rings

In this paper, we constructed test equipment for a rotating machine that uses a superconducting bulk rotor and performed a rotation test. When a superconducting bulk rotor is used, a fluctuating magnetic field generates ac loss, it is possible to decrease its trapped magnetic flux. Performance of the rotating machine under test was influenced by the ac loss generated by a fluctuating ac magnetic field. We modeled the motor used in this paper on an axial-type synchronous motor, where the magnetic field generated by the stator coils causes the rotor to rotate. We then measured the influence of the stator coils on the superconducting bulk rotor. First, we confirmed that the temperature of the bulk rotor modules was properly controlled and could generate a trapped magnetic flux equal to that during zero-field-cooled magnetization. A technique for magnetizing two or more bulks concurrently was used. Next, we performed the rotation test at low speed. The maximum rotational speed during the test was 300 r/min. The operation time at a steady-state speed was 600 s. The maximum value of the generated magnetic field of the stator coils was 50 mT. Finally, we confirmed that a shielding ring made of superconducting wire decreased the influence of a fluctuating magnetic field.