Variable-Structure Stacked Cable for Uniform Coil Critical Current
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Solution Overview
Problem
The critical current of second-generation high-temperature superconducting tapes is unevenly distributed due to uneven magnetic fields in strong-field magnets, leading to the 'buckets effect' where the actual running current is limited by areas with the lowest critical current.
Innovation Solution
A variable-structure stacked cable topology is developed, comprising sequentially connected sections of stacked cables with a combination of superconducting tapes and copper tapes, arranged to form a tiled structure and packaged using soldering tin. This design allows for a uniform critical current distribution along the length of the coil when twisted into a pancake coil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform stacked cable structure is used throughout the coil, then the manufacturing process is simple, but the critical current distribution becomes uneven due to varying magnetic fields, leading to the buckets effect
Solution Approach 1:
The patent applies local quality by varying the cable structure along the length of the coil to match the local magnetic field conditions. Different sections of the coil have different numbers of superconducting tapes stacked, with sections experiencing stronger magnetic fields having more tapes to compensate for the reduced critical current density. This creates a non-uniform cable structure that is optimized for local conditions, resolving the contradiction between manufacturing simplicity and current distribution uniformity.
Solution Approach 2:
The coil is divided into multiple sections along its length, with each section having a specific number of superconducting tapes stacked based on the magnetic field strength in that region. This segmentation allows the cable structure to be optimized locally for each section's magnetic field conditions, preventing the buckets effect while maintaining overall system reliability.
2Reliability
If more superconducting tapes are used in high magnetic field areas, then the critical current distribution becomes more uniform, but the material consumption and manufacturing complexity increase
Solution Approach 1:
The patent uses local quality to concentrate superconducting tapes only where needed - in sections experiencing stronger magnetic fields where the critical current density is reduced. Sections with weaker magnetic fields use fewer tapes, optimizing material utilization. This approach achieves uniform critical current distribution while minimizing overall superconducting tape consumption compared to a uniform high-density design.
3Power
If the stacked cable is twisted into a coil, then the magnetic field performance is improved, but the anisotropic characteristics of the tape cause current to be randomly shared and shunted, reducing robustness
Solution Approach 1:
The cable is constructed with multiple discrete superconducting tapes stacked and independently soldered to copper stabilizer layers. This segmented structure allows each tape to carry current more uniformly, reducing random current sharing and shunting effects that occur in twisted configurations. The segmentation maintains robustness while enabling the coil to achieve its magnetic field performance.
Solution Approach 2:
The patent uses composite materials by stacking superconducting tapes with copper stabilizer layers and soldering them together. This composite structure combines the high critical current density of superconducting materials with the excellent electrical conductivity and mechanical properties of copper, creating a robust cable that maintains reliable current sharing even when twisted into a coil configuration.
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 variable-structure stacked cable topology achieves a more uniform critical current distribution across the coil, enhancing magnetic field parameters and minimizing superconducting tape material consumption.
Implementation Method 1
the common preparation process for the stacked cable in the industry is to directly press and package a plurality of second generation high-temperature superconducting tapes by using soldering tin at 215° C.
Implementation Method 2
The second generation high-temperature superconducting material (REBCO coated conductor) has become a research hotspot in the field of power equipment due to the characteristics of no direct current resistance loss and high conduction current density
Implementation Method 3
the critical current of the second generation high-temperature superconducting tape is greatly influenced by the magnetic field of a vertical tape
Data Source
AI summary
A variable-structure stacked cable topology includes: a plurality of sections of stacked cables. The plurality of sections of the stacked cables are connected sequentially. The sections of the stacked cables includes a plurality of base tapes at an equal quantity. The plurality of base tapes are connected mutually. At least one of the plurality of base tapes is a superconducting tape. A cable topological structure is formed by sequentially connecting a plurality of sections of stacked cables. Each of the sections of the stacked cables is provided with superconducting tapes or a combination of superconducting tapes and copper tapes to form a variable-structure cable topological structure. By packaging a different number of superconducting tapes in each area, this section of cable can be twisted into a coil in such a way that a critical current of the whole coil can be approximately uniform along a length direction of the cable.