Low-Resistance Connection for High-Temperature Superconducting Wires

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Solution Overview

Problem

Conventional methods for joining high-temperature superconducting wires face challenges in controlling temperature, achieving sufficient mechanical strength, aligning crystal orientations, and reducing connection time, leading to higher electrical resistance and lower critical current.

Innovation Solution

The use of a high-temperature superconducting bulk body with a lower melting point than the wire, allowing for crystal growth with the wire's superconducting layer as a seed crystal, aligning orientations and enhancing mechanical strength, while reducing connection time to a few days.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the melt diffusion method is used to join REBCO superconducting wires, then electrical resistance is reduced, but temperature control becomes difficult and mechanical strength is insufficient

Engineering Contradiction:
Improveelectrical resistanceVSAvoidtemperature control
Core Design Contradiction:
ReliabilityVSTemperature

Solution Approach 1:

A buffer layer with intermediate melting point is introduced between the superconducting wires to facilitate joining. The buffer layer melts at a lower temperature than the REBCO superconducting layer, enabling temperature-controlled joining without damaging the superconducting material while maintaining low electrical resistance through the intermediary medium.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The joining process utilizes controlled temperature parameters where the buffer layer undergoes phase change at a specific temperature range. By controlling the heating temperature to be between the melting point of the buffer layer and the REBCO layer, the process achieves reliable joining with improved temperature control and mechanical strength.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If the melt diffusion method is used to join REBCO superconducting wires, then electrical resistance is reduced, but mechanical strength becomes insufficient

Engineering Contradiction:
Improveelectrical resistanceVSAvoidmechanical strength
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The joining structure comprises a composite of superconducting wires and buffer layer material. The buffer layer acts as a bonding matrix that provides mechanical strength while maintaining superconducting properties, creating a composite structure that simultaneously achieves low electrical resistance and high mechanical strength.

Inventive Principle:
Principle #40Composite materials

3Reliability

If connection is performed using conventional methods, then connection success is achieved, but connection time becomes excessively long

Engineering Contradiction:
Improveconnection successVSAvoidconnection time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The joining process exploits the phase transition of the buffer layer from solid to liquid and back to solid. By heating the buffer layer to its melting point and then cooling it, rapid bonding occurs in a controlled manner, significantly reducing connection time while ensuring connection success through the phase change mechanism.

Inventive Principle:
Principle #36Phase transitions

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This method enables low-resistance connections with improved critical current and mechanical strength, allowing for faster and more efficient joining of high-temperature superconducting wires.

Implementation Method 1

the high-temperature superconducting bulk body can undergo crystal growth, using the high-temperature superconducting layer as a seed crystal, through heating up to a temperature at which only the high-temperature superconducting bulk body liquefies

Methodology Applied
Scientific EffectCrystal growth: Crystallisation

Implementation Method 2

heating up to a temperature at which only the high-temperature superconducting bulk body liquefies

Methodology Applied
Scientific EffectMelting: Melting

Data Source

PatentEP3104374B1Low-resistance connection body for high-temperature superconducting wire material and connection method
Publication Date: 2019.12.18 RIKEN CO LTD
  • EP3104374B1 patent drawingFigure 1(a)~1(b)
  • EP3104374B1 patent drawingFigure 2
  • EP3104374B1 patent drawingFigure 3

AI summary

Provided is a low-resistance connection body for a high-temperature superconducting wire, in which a high-temperature superconducting bulk body and a high-temperature superconducting wire including a high-temperature superconducting layer are connected to each other, wherein a melting point of the high-temperature superconducting layer is higher than a melting point of the high-temperature superconducting bulk body; the high-temperature superconducting layer and the high-temperature superconducting bulk body are in contact at a connection site of the high-temperature superconducting wire and the high-temperature superconducting bulk body; and a surface of the high-temperature superconducting bulk body that is in contact with the high-temperature superconducting layer is crystallized due to crystal growth. Two high-temperature superconducting wires can be connected, with low resistance, through connection of the two high-temperature superconducting wires to one high-temperature superconducting bulk.