Proof-of-concept of a millisecond-scale electromagnetic levitator using high-temperature superconducting coils

This paper proposes a millisecond-scale electromagnetic levitator using high-temperature superconducting (HTS) coils. The proposed apparatus consists of an AC power supply, short-circuit switches, an aluminum plate, and two HTS coils. The HTS coils are wound in opposite directions and electrically connected in parallel. Thus, in a symmetric current distribution, the magnetic fluxes generated by the two HTS coils ideally cancel each other. However, in a sudden asymmetric current distribution created by the short-circuit switches, the magnetic fluxes are not cancelled, and the effective magnetic flux induces an eddy current in the aluminum plate placed above the HTS coils. The magnetic flux generated by the eddy current in the aluminum plate and the effective magnetic flux generated by the HTS coils together generate the repulsive force to levitate the aluminum plate. In this paper, numerical calculations and experimental verification of the repulsive force are performed. We show that this apparatus is able to provide a levitation force that we expect will be helpful for devices that need fast switching behavior of the levitation force.