Characteristics Analysis at High Speed of Asynchronous Axial Magnetic Coupler for Superconducting Flywheel Energy Storage System

High temperature superconducting flywheel energy storage system (HTS FESS) based on asynchronous axial magnetic coupler (AMC) is proposed in this paper, which has the following possible advantages: the generator/motor (G/M) can be installed outside of the vacuum chamber with the torque being transferred by the magnetic coupler, and the stator liquid cooling system is not needed; the idle loss of G/M during the stage of energy maintaining can be eliminated by disconnecting the coupler from the system by the magnetic field shielding device. Up to now, there has been little research on AMC for high-speed application. In this paper, the performance parameters of the torque, axial force, and magnetic flux density in the middle of airgap and at the mean radius are calculated based on finite-element model. The prototype used to update the 30 kJ/2 kW HTS FESS developed in 2014 is manufactured, and the test platform of transfer characteristics at high speed is established. The experiments at high speed are conducted and the measured results show a good agreement with the simulation results. Meanwhile, the correlations between the magnetic flux density, the axial force, and HTS FESS are analyzed. At last, the feasibility of AMC used for HTS FESS is validated by the charge and discharge experiment. The system efficiency and technical problems are analyzed.