Insulation-Coated Superconducting Wire for Strain-Tolerant Coil Winding
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Solution Overview
Problem
Conventional superconducting wires, such as Nb3Sn, are weak against strain due to thermal shrinkage differences in composite materials, limiting their use in large magnets and requiring strict control of processing conditions for enamel coating, which prolongs production time and reduces the stability of superconducting properties.
Innovation Solution
An insulation-coated compound superconducting wire with a core-like compound superconductor part, a cylindrical reinforcing part, and a stabilizing part, where an electric insulation part is applied on the outer surface, enhancing tensile strength and critical current values by managing strain and stress through specific bending and heat treatment processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compound superconducting wire is heat-treated to generate Nb3Sn, then superconducting properties are achieved, but the wire becomes weak against strain and cannot be wound
Solution Approach 1:
The patent applies preliminary bending strain to the compound superconducting wire before heat treatment. This pre-straining creates compressive residual stress in the wire that counteracts the tensile stress generated during subsequent winding operations, allowing the wire to be both heat-treated for superconducting properties and later wound into coils without damage
Solution Approach 2:
The patent changes the stress state parameter of the wire by applying controlled bending strain during manufacturing. This creates a residual stress profile that transforms the wire from being tension-sensitive to being capable of withstanding winding operations, effectively changing its mechanical behavior without altering its superconducting properties
2Power
If large magnet is produced by wind-and-react process, then superconducting coil is formed, but large heat treatment furnace is required which limits magnet size
Solution Approach 1:
The patent performs the heat treatment action before the winding action (react-and-wind process). The wire is heat-treated in a small furnace to generate Nb3Sn, then subsequently wound into the final coil configuration. This reverses the conventional sequence and eliminates the need for a large furnace capable of accommodating the entire magnet
Solution Approach 2:
The patent separates the heat treatment process from the winding process. The wire is heat-treated in segments or in a compact form before being assembled into the final large-scale magnet configuration, allowing small furnaces to produce components for large magnets
3Reliability
If critical current density is increased by twisting superconducting strands, then high magnetic field capability is achieved, but large strain cannot be applied to compound-based superconducting wire
Solution Approach 1:
The patent applies preliminary bending strain to twisted compound superconducting wires before heat treatment. This pre-straining creates compressive residual stress that compensates for the tensile stress generated during winding, enabling both high critical current density through twisting and subsequent winding capability
4Reliability
If enamel coating is applied to compound superconducting wire, then insulation is provided, but processing conditions must be strictly controlled which prolongs production time
Solution Approach 1:
The patent applies preliminary bending strain before enamel coating, which stabilizes the wire structure and reduces variability in the coating process. This allows for more relaxed processing conditions and faster production while maintaining insulation quality
Solution Approach 2:
The patent changes the stress state of the wire through preliminary bending, which affects how the enamel coating adheres and distributes on the wire surface. This parameter change enables more robust coating conditions that are less sensitive to minor variations in processing
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
The insulation-coated wire exhibits improved superconducting characteristics, increased tensile strength, and enhanced wire winding properties, enabling the production of high-performance superconducting coils with improved durability and efficiency.
Implementation Method 1
a compound superconducting wire including a core-like compound superconductor part (11), a cylindrical reinforcing part (12), and a cylindrical stabilizing part (13)
Implementation Method 2
it is necessary to perform a compound generation heat treatment for generating Nb 3 Sn in a furnace under vacuum or in an inert gas atmosphere at a predetermined temperature of 600°C or higher
Implementation Method 3
the compound-based superconductor wire is constituted as a composite material including a plurality of materials different from each other, thus, thermal shrinkage of the respective materials constituting the compound-based superconductor wire differs from each other when cooled, and compressive residual strain in the superconductor is generated
Data Source
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AI summary
The present invention provides: an insulation-coated compound superconducting wire which has excellent superconducting characteristics, exhibits a tensile strength equal to or larger than that of the conventional compound superconducting wire at both room temperature and extremely low temperature, also has excellent winding property, and enables a superconducting coil to be commercially produced; and a rewinding method thereof. The insulation-coated compound superconducting wire 1 according to the present invention includes: a compound superconducting wire 10 having a compound superconducting part 11 which includes a first matrix 16 and a plurality of compound superconducting filaments 15 containing compound superconducting phases, a reinforcing part 12 which is disposed on the outer circumferential side of the compound superconducting part 11 and includes a plurality of reinforced filaments 18, a second matrix 19 and a second stabilizing material 20, and a stabilizing part 13 which is disposed on at least one side among the inner circumferential side and the outer circumferential side of the reinforcing part 12; and an electrical insulation part 30 which covers the outer circumferential surface of the compound superconducting wire 10, in which the insulation-coated compound superconducting wire 1 has a critical current value (Ic) larger than that of the compound superconducting wire 10 before being covered with the electrical insulation part 30.