Liwei Jing

Wireless Power Transfer Using High Temperature Superconducting Pancake Coils

It is well known that the efficiency of a wireless power transfer (WPT) system depends on the resistance of the transmitting and receiving coils, especially for the case of low frequency. Since the ac loss of high temperature superconductors (HTS) is much lower than that of conventional conductors, using high temperature superconductors for WPT system is a good way to increase power transfer efficiency. Here, several kinds of WPT experiments were designed and conducted by use of HTS and conventional conductor (copper) coils, respectively. The results are presented and analyzed. It is shown that the behavior of HTS WPT system is similar to that of a conventional WPT system, but the efficiency of WPT system is much higher by use of HTS coils and HTS coil is more suitable for being as a transmitting coil than as a receiving one.

Experimental and numerical study of frequency-dependent transport loss in YBa2Cu3O7–δ coated conductors with ferromagnetic substrate and copper stabilizer

Although AC transport losses of YBa2Cu3O7−δ (YBCO) coated conductors (CCs) have been studied extensively, the frequency dependence of transport losses still needs more investigations. This paper presents a study on the frequency dependence (in the range of 50–1000 Hz) of the transport losses in YBCO CCs with ferromagnetic substrate and copper stabilizer by the use of both experimental and finite element methods (FEMs). The finite element model (FEM) is based on H‐formulation and E-J power law, and calculated AC transport losses accord with the experimental ones. The contributions of ferromagnetic (Ni-5at.%W substrate), eddy current (conventional metal), and hysteresis (superconducting YBCO) losses are extracted. It is shown that the AC transport loss per cycle increases with the frequency due to the growing contribution of eddy current loss. More than 80% of eddy current loss comes from the copper stabilizer adjacent to the ferromagnetic substrate. The influence of magnetic substrate on AC loss is also studied, and it is found that YBCO CCs with non-magnetic substrates are more suitable for high-frequency applications.Although AC transport losses of YBa2Cu3O7−δ (YBCO) coated conductors (CCs) have been studied extensively, the frequency dependence of transport losses still needs more investigations. This paper presents a study on the frequency dependence (in the range of 50–1000 Hz) of the transport losses in YBCO CCs with ferromagnetic substrate and copper stabilizer by the use of both experimental and finite element methods (FEMs). The finite element model (FEM) is based on H‐formulation and E-J power law, and calculated AC transport losses accord with the experimental ones. The contributions of ferromagnetic (Ni-5at.%W substrate), eddy current (conventional metal), and hysteresis (superconducting YBCO) losses are extracted. It is shown that the AC transport loss per cycle increases with the frequency due to the growing contribution of eddy current loss. More than 80% of eddy current loss comes from the copper stabilizer adjacent to the ferromagnetic substrate. The influence of magnetic substrate on AC loss is also st...

Wireless Power Transfer With HTS Transmitting and Relaying Coils

Using a high-temperature superconducting (HTS) coil as the transmitting coil is an optional way to increase the efficiency and the distance of a wireless power transfer (WPT) system. In practical cases, receiving coils might be not only one, or not convenient to get a low-temperature environment, or not in the same sizes with the transmitting coil. Thus, we constructed a WPT system from one HTS coil to two copper coils, and one of the copper receiving coils had a different size from the HTS transmitting coil. In addition, we placed one HTS relaying coil between the transmitting coil and the receiving coils to increase the efficiency and the distance. Based on this system, we conducted several experiments and analyzed the results. We found that a denser coil could obtain more power in an HTS WPT system and that WPT from one HTS coil to two copper coils was more efficient than WPT from the same HTS coil to one of the two copper coils. We also demonstrated that an appropriate layout of the HTS relaying coil can increase the HTS WPT efficiency.

Influence of substrate magnetism on frequency-dependent transport loss in HTS coated conductors

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., nonmagnetic, weakly magnetic, and 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 nonmagnetic substrate. Both hysteresis loss in HTS layer and eddy current loss in conventional metal increase with the enhancement of substrate magnetism.

Investigation of Flux-Coupling Type Superconducting Fault Current Limiter With Multiple Parallel Branches

The flux-coupling type superconducting fault-current limiter (FC-SFCL) is discussed in this paper. Considering the shortcomings of conventional inductive and resistive SFCLs, two novel FC-SFCLs with multiple parallel branches are carried out. Considering the characteristics of YBCO tapes in 77-K LN2 environment, the design scheme of the HTS module is studied according to the impedance parameters, the number of parallel branches, and insulation distance. Furthermore, the electromagnetic analysis and parameter calculation of the module are performed. In order to identify the status of the HTS module in normal operating, current limiting, and reclosing processes, the status identification method for HTS module is analyzed. Finally, the possible application of FC-SFCL in power grid is discussed.

Quench Behaviors of Monofilament Iron-Based Sr 0.6 K 0.4 Fe 2 As 2 Tape With Ag Sheath at Different Temperatures

For practical application, stability investigations of Sr0.6K0.4Fe2As2 conductors are of great importance. In this paper, quench development and propagation in Ag sheath are experimentally and numerically investigated. Measurements are performed as a function of transport current for several operating temperatures between 19 and 35 K. This work focuses on the evaluation of quench development and the estimation of normal zone propagation velocity (NZPV) and minimum quench energy (MQE). The experimentally obtained temperature dependence of NZPV is compared with a simplified adiabatic model. In addition, the NZPV and the MQE of the sample are compared with those of a low-temperature superconductor (LTS) and a high-temperature superconductor (HTS). According to the results, the basic quench characteristics fit between those of LTS and HTS materials.