There are some disadvantages in conventional cryogenic liquid pumps (CLPs) with mechanical bearings, such as difficult lubrication and short working life. In this paper, we propose a new structure of CLP-submerged cryogenic disk motor-pump with superconducting magnetic bearing (SMB). The impeller and the rotor of the disk motor are combined as the suspension rotor of the disk motor-pump. The suspension rotor which is supported by SMB system, rotates frictionlessly with self-stabilized. The SMB system includes a radial-type SMB, an axial-type permanent magnet bearing, and an axial flux disk motor. Theoretical calculations and experimental measurements of levitation forces in the SMB system are carried out. The levitation force of radial-type SMB is calculated by using H -formulation finite-element model in COMSOL. The kinetic model of the suspension rotor is established to ensure the force balance and torque balance. The results demonstrate the feasibility of the proposed submerged cryogenic disk motor-pump with SMB.

The magnetism of substrate has significant influence on the transport loss in high temperature superconducting (HTS) coated conductors (CCs). Taking three types of substrates (i.e. non-magnetic, weakly magnetic, strongly magnetic) into account, a study on the frequency dependence (in the range of 10-1000 Hz) of transport loss in HTS CCs with these substrates is performed numerically and experimentally. Different loss components and magnetic field profile are calculated individually to clarify the effect of substrate magnetism. Results show that HTS CCs with magnetic substrate exhibit higher transport loss than CCs with non-magnetic substrate (NMS). Both hysteresis loss in HTS layer and eddy current loss in conventional metal increase with the enhancement of substrate magnetism.

The numerical study on the transport loss reduction in REBCO double pancake (DP) coil is presented in this paper. An axisymmetric finite element model based on H formulation and E-J power law is established. The influence of the gap between two pancakes on the transport losses of DP coils is investigated. The use of magnetic flux diverters to reduce the ac loss of the DP coil by decreasing the perpendicular magnetic field applied to the tape surface is also studied. It is found that the perpendicular magnetic field is decreased clearly by attaching the flux diverter in the middle and end positions of DP coil. Compared with the ac losses of DP coils without flux diverters, the use of flux diverters can decrease the ac losses by 70% when the applied current is at half the critical current of DP coil.

There are axial and radial electromagnetic forces between stator and rotor of axial flux disk motor besides the useful torque. The electromagnetic forces act on the rotor and are crucial to the stable operation in magnetic levitation applications driven by disk motor. This paper concerns the behaviors of axial and radial electromagnetic forces of disk motor using for cryogenic submersible pump. It is measured experimentally that the electromagnetic properties of motor materials, including the electrical conductor and magnetic conductor materials, in room temperature (RT) and liquid nitrogen (LN₂) environment. Then, the 3D FEM of three-phase asynchronous disk motor in RT environment is built which is also validated by the RT experimental tests. Finally, the behaviors of axial and radial electromagnetic forces in LN₂ environment are investigated using the modified FEM taking account of the effect of cryogenic environment on the motor material. It is concluded that the axial electromagnetic force decreases monotonously with the increasing air-gap thickness or the decreasing rotating speed. When the rotor exhibits radial eccentricity, there is a restoring radial electromagnetic force, trying to pull the rotor back to the central position. The radial electromagnetic force increases with the increasing rotational speed and radial eccentric displacement.

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 is few 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 air-gap and at the mean radius are calculated based on finite-element model (FEM). 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.