Design of the HTS Magnetic Bearing Rotor Incorporated the Secondary of the Induction Motor

This paper proposes the design of a high-temperature superconductor (HTS) magnetic bearing rotor incorporated the secondary of the induction motor. The rotor is rotated using the principle of the induction motor. The structure of the rotor is determined by electromagnetic field analysis. The thickness of aluminum is analyzed so that sufficient torque is generated to rotate the rotor. The magnetic shield is used to guide the rotating field to the outside without getting inside the rotor. The air gap increases the reluctance and suppresses flux from the inside of the magnetic shield toward the yoke. The thickness of the magnetic shield and the air gap are changed, and the appropriate thickness is analyzed so that flux inside the rotor would not be disturbed by the influence of the rotating field. Thus, the HTS magnetic bearing rotor incorporated the secondary of the induction motor is designed. In addition, the rotational characteristic is measured at levitation gap g = 8, 10 mm. As a result, the rotor rotates up to 500 rpm by the rotating field of the induction motor. On the other hand, force other than the rotational direction is applied to the rotor, and vibration occurs. The vibration of the rotor at levitation gap g = 8 mm decreases by 20% compared with that of g = 10 mm. Because linkage flux of the HTS surface at g = 8 mm increases by 18% compared with that of g = 10 mm, the pinning force that supports the rotor increases. It is shown that stability of the rotor improves as the levitation gap decreases and flux on the HTS surface increases.