Yota Ichiki

Numerical analysis of AC loss characteristics of YBCO coated conductors arranged in parallel

AC losses and electromagnetic phenomena in assembled conductors composed of YBCO coated conductors arranged in parallel were studied by finite element method (FEM). The analysis tool is based on the current vector potential method with thin-plate approximation and with strongly nonlinear E-J characteristics (E: electric field, J: current density) of superconductor. In this paper the dependence of AC losses and electromagnetic phenomena on the intervals between the conductors was investigated.

Influence of Inhomogeneous Superconducting Properties of YBCO Thin Film on Current Limiting Characteristics

This paper describes numerical analysis of current limiting characteristics of YBCO thin film with inhomogeneous superconducting properties. The analysis tool uses a finite element method (FEM) based on current vector potentials. First, the validity of the analysis tool was verified by comparing with experimental results using small samples. Then we analyzed large-size meander-shaped thin films and discussed the influence of inhomogeneous superconducting properties of YBCO thin film on current limiting characteristics.

FEM analysis of current limiting devices using superconducting thin film and AC losses of YBCO coated conductor

A numerical analysis tool has been developed to study electromagnetic characteristics of high‐temperature superconducting thin film used for a resistive‐type fault current limiter (FCL) and coated conductor. It adopts the finite element method based on current vector potentials with thin‐plate approximation. Transport current, temperature dependence and strong non‐linearity of electromagnetic properties, and state transition of superconductor are taken into account by solving a three‐dimensional coupled problem of electromagnetic field, an electric circuit and thermal field. Then using this numerical analysis tool the current imbalance and current limiting characteristics of a FCL device, the influence of inhomogeneity of superconducting properties on them, and AC losses in YBCO coated conductor are studied.

Verification of metal layer design for large-capacity superconducting fault current limiting elements using YBCO thin film

A superconducting fault current limiter (FCL) is one of the most attractive solutions to an increase of short-circuit current in electric power networks. The authors have studied resistive type FCLs using YBCO thin film superconductor with the patterning of superconducting and metal layers to increase the capacity of their current and voltage. A new design concept of fault current limiting element has been proposed, which has a meander-shaped gold layer on a wide I-shaped YBCO thin film. Experimental study and comparison between experimental and numerical analysis results verify the validity of the new FCL design concept.

Transient Electromagnetic Phenomena during Current Limiting Process in YBCO Thin Film

In order to design a reliable and high-performance fault current limiter, it is necessary to estimate the influences of the inhomogeneous superconducting properties on the current limiting process and S-N transition. This paper describes the measurements of transient electromagnetic phenomena in YBCO thin film using pick-up coils to observe current-sharing process and change of current distribution. At first current distribution in a steady state was measured. And then transient phenomena caused by applying an overcurrent to YBCO thin film covered with a silver layer were measured.