Superconducting Coil Parallel Strands AC Loss Reduction
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Solution Overview
Problem
Superconducting coils face challenges in AC applications due to high AC losses and vulnerability to circulating currents, which can lead to overheating and damage, especially when using oxide superconducting wires with low mechanical strength and high critical current requirements.
Innovation Solution
A superconducting coil structure is designed with multiple layers of parallel superconductor units, where each unit consists of electrically separated superconducting elements and non-superconducting elements, allowing for cancellation of perpendicular interlinkage magnetic flux and distribution of electromagnetic forces, reducing AC losses and enhancing current capacity while preventing burn-out during over-current events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple superconducting wires are arranged in parallel to increase current capacity, then the current carrying capability is improved, but circulating current increases causing AC losses and potential damage
Solution Approach 1:
The superconducting wire is divided into multiple independent strands, each with its own magnetic shielding layer. This segmentation isolates the magnetic flux experienced by each strand, preventing inter-strand circulating currents while maintaining high current capacity through parallel arrangement.
Solution Approach 2:
A magnetic shielding layer (intermediary structure) is introduced between superconducting strands to block magnetic flux penetration. This mediator prevents the magnetic flux that causes circulating currents from directly interacting with adjacent strands, thereby reducing AC losses.
2Loss of energy
If transposition is performed to reduce circulating current, then AC losses are reduced, but the number of unstable points increases due to bending forces on oxide superconductors
Solution Approach 1:
The magnetic shielding function is extracted from the transposition operation and integrated into the wire structure itself through dedicated shielding layers. This eliminates the need for frequent transposition to control circulating currents, thereby reducing mechanical stress points on the brittle oxide superconductor.
Solution Approach 2:
Magnetic shielding layers are pre-installed on each strand before assembly into the cable. This preliminary protective action prevents magnetic flux-induced circulating currents without requiring subsequent transposition operations, maintaining mechanical integrity throughout the cable length.
3Temperature
If oxide superconductors are used to achieve high-temperature operation, then operating cost is reduced, but mechanical strength decreases making the material more vulnerable to bending
Solution Approach 1:
The superconducting cable employs a composite structure combining oxide superconducting strands with magnetic shielding layers and structural support elements. This composite design protects the mechanically vulnerable oxide superconductor while maintaining its high-temperature superconducting properties.
Solution Approach 2:
Different regions of the cable structure have specialized functions: oxide superconducting strands provide high-temperature superconductivity, magnetic shielding layers provide flux protection, and outer structures provide mechanical support. This local specialization allows the oxide superconductor to operate at high temperatures without bearing mechanical bending stresses.
4Loss of energy
If the number of transposed parts is increased to suppress circulating current, then circulating current is reduced, but the number of unstable points increases
Solution Approach 1:
The cable is segmented into multiple independently shielded strands, each immune to magnetic flux-induced circulating currents. This segmentation eliminates the need for transposition to suppress circulating currents, simplifying the overall cable structure while maintaining low AC losses.
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 structure effectively suppresses AC losses, increases current capacity, and prevents conductor burn-out by distributing electromagnetic forces and sharing current through non-superconducting elements, ensuring stable operation even during high current conditions.
Implementation Method 1
the coil structure is configured to cancel any perpendicular interlinkage magnetic flux acting among various superconductor elements of the secondary parallel superconductor unit by the distribution of the magnetic field generated by the superconducting coil
Implementation Method 2
a superconducting wire made of a metal superconductor that remains in a superconducting state at a very low temperature of 4K
Data Source
AI summary
In one embodiment, a superconducting coil includes a tertiary parallel superconductor unit (60) composed of superposed in parallel a plurality of layers of secondary parallel superconductor units (50). The layers of secondary parallel superconductor units include a plurality of superconductor elements (40) arranged in parallel along the axial direction of the coil, forming a superconducting conductor unit. The tertiary parallel superconductor unit is wound on a bobbin (55). In another embodiment, the superconducting coil includes one or more layers of the secondary parallel superconductor unit wound on the bobbin. In both embodiments, the secondary parallel superconductor unit can include at least one non-superconducting conductor element (70). The layer of the secondary parallel superconductor unit forming an outer side of the tertiary parallel superconductor unit can include at least one non-superconducting conductor element. A layer of non-superconducting conducting or high-strength insulating supporting member (71) of electromagnetic force can be formed on the outer side of the tertiary parallel superconductor unit.