Wireless power transfer (WPT) is of increasing interests today. High temperature superconducting (HTS) WPT has been demonstrated to be more efficient than copper WPT. In our previous work, we found that the efficiency of WPT from a copper coil to a HTS coil is lower than the efficiency of WPT from the same HTS coil to the same copper coil. Thus, the transmitter and the receiver are asymmetric and this asymmetry degrades WPT performance. In this paper, it is demonstrated theoretically and experimentally that for WPT between a HTS coil and a copper coil: asymmetry does exist and influences properties; the root of the asymmetry is the different resistances between the HTS coil and the copper coil; the effects of the asymmetry can be eliminated by optimizing the load; the proposed theoretical calculation fits the experimental results well.

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.

A facility capable of testing superconducting cables with current of tens of kA is essential for the development of large superconducting magnets. A superconducting transformer (SCT) is a suitable choice as a high DC current source for testing superconducting cables. In this work, we will present our experimental results of a SCT up to output current of 45 kA. The properties of this SCT is characterized at 4.2 K. Its behaviors during quenches at different current levels are studied.

In experimental studies of HTS quench behaviors, different experimental protocols, especially heater configurations, including heater pulse duration and magnitudes, can lead to inconsistent measured results. In this work, mainly based on experimental measurements, the quench characteristics of REBCO samples, including minimum quench energy (MQE) and normal zone propagation velocities (NZPV), are investigated with various heater configurations. The relations between the measured quench characteristics and the heater configurations demonstrated that the measured MQE increased with the increasing heater pulse duration employed in the quench experiments, and the heater pulse duration had better be smaller than the diffusion time constant over minimum propagation zone; and the heater pulses adopted in the quench measurements for the stacks can be longer than that for the single tape.

The radial crimping process is a crucial step in fabricating stacked high-temperature superconducting (HTS) cable-in-conduit conductor (CICC) made with rare earth barium copper oxide (REBCO) HTS tapes for the application of large-scale HTS magnets at low temperatures. This paper presents theoretical research on the forming principle and correlated law of the radial crimping process for stacked HTS CICC. Firstly, a finite element model is developed to simulate the forming process of the conductor under the conditions of the radial crimping process steps. Subsequently, the changes in the wall thickness of the jacket, the stress-strain distribution of the conductor, and the deformation characteristics of the stacked tapes during the forming process are analyzed. Finally, by comparing the calculated results with the experimental ones, the effects of different crimping steps on the forming quality of the conductor are studied. This research can provide significant references for optimizing the manufacturing process of stacked HTS CICCs and improving the overall performance of the conductor.