Analysis on magnetic coupling characteristics and carrying capacity of superconducting rotor magnetic levitation structure

Abstract

The high-speed rotating superconducting rotor can be used as a sensor to measure angular speed or angular position. Mass unbalance and oblateness of superconducting rotor are the main error sources to measure angular speed or angular position. General Electric company has developed an superconducting rotor magnetic suspension device with an accuracy of 0.005^°per hour, but its rotor structure is very complex. So it is difficult to process and assemble with extremely small mass-unbalance and small oblateness, which limits the further improvement of its accuracy. According to this, in this paper we introduce a magnetic support structure with a simple superconducting rotor compared with rotor made by General Electric company. The rotor sphere is a closed structure with no theoretical mass eccentricity. Its electromagnetic structure is simpler than General Electric company’s, and the stator coil is the torquer coil at the same time. The stator coil is used to accelerate the rotor, while the torquer is used to make the rotor erect. Based on the theory of superconducting electrodynamics and the finite element method, the characteristics of the magnetic suspension structure are analyzed. The magnetic field coupling effect of the stator and the suspension coils on the surface of the superconducting rotor are studied, and their influence on magnetic supporting force is also analyzed. The current direction of the two suspension coils should be opposite, otherwise the rotor will produce forced vibration, which will make it difficult to accelerate the superconducting rotor. Then the magnetic circuit theory and the finite element method are used to model the magnetic circuit of the magnetic levitation structure, and the critical carrying capacity of the magnetic suspension structure is calculated and the optimal suspension conditions are given. Finally, a method to optimize its carrying capacity is designed. Therefore, the currents of the suspension coils are controlled by the acceleration of superconducting cavity. Through this method, the maximum bearing capacity of the magnetic levitation structure can be increased by 78% compared with that of fixed optimal suspension current support. The analysis results provide a reference for the structural design and optimization of the superconducting rotor magnetic levitation system.