Mechanical superconducting switch
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Solution Overview
Problem
Conventional superconducting switches for MRI magnets suffer from high heat dissipation and limited 'off' resistance, requiring ancillary coils and thermal heaters, which are unstable and inefficient, especially in cryogen-free designs where cooling power is limited.
Innovation Solution
A mechanically operated superconducting switch using the wire ends of the magnet coils themselves, eliminating the need for ancillary coils and thermal heaters, with mechanically actuated BiPb or similar superconducting blocks providing infinite 'off' resistance and minimizing heat dissipation by using copper matrix wires for stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional superconducting switches use ancillary coils with CuNi alloy matrix, then switching operation can be achieved, but the switch becomes susceptible to temperature and wire instabilities and flux jumping
Solution Approach 1:
The invention extracts and eliminates the ancillary coil component from the superconducting switch design. Instead of using a separate CuNi alloy matrix coil, the patent uses the magnet coils' own superconducting wire ends directly as the switching element, thereby removing the source of temperature and wire instabilities while simplifying the overall device structure
Solution Approach 2:
The magnet coils serve a dual function: they generate the magnetic field and simultaneously act as the switching element. The wire ends of the magnet coils are used directly as the superconducting switch contacts, eliminating the need for dedicated ancillary switching coils and reducing device complexity
2Ease of operation
If conventional switches use thermal heaters to open and close the switch, then switching operation can be achieved, but heat dissipation increases and cooling power is exceeded
Solution Approach 1:
The invention replaces the thermal field-based switching mechanism (heaters) with a mechanical field-based mechanism. A mechanical actuator directly opens and closes the superconducting contacts without thermal conversion, eliminating the need for heaters and the associated heat dissipation that exceeds cryogenic refrigerator cooling power
Solution Approach 2:
The mechanical actuator provides periodic opening and closing action of the superconducting contacts. This periodic mechanical action enables switching operation without continuous heat generation, allowing the cryogenic refrigerator to maintain cooling without being overwhelmed by heater dissipation
3Productivity
If conventional switches have limited open-circuit resistance, then switching can be achieved, but ramp rate is limited and heat dissipation occurs during energization
Solution Approach 1:
The invention changes the electrical resistance parameter of the switch in the off-state by using mechanically separated superconducting wire ends. This configuration provides extremely high open-circuit resistance, enabling fast ramp rates during magnet energization and de-energization while minimizing heat dissipation, as the high resistance prevents significant current flow and associated I²R heating
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 solution achieves persistent current switching with resistance as low as 10−13Ω, significantly reducing heat dissipation and increasing ramp rates, while utilizing the cryogenic refrigerator's cooling power effectively, outperforming previous designs in stability and performance.
Implementation Method 1
A mechanically operated superconducting switch using the wire ends of the magnet coils themselves, eliminating the need for ancillary coils and thermal heaters, with mechanically actuated BiPb or similar superconducting blocks providing infinite 'off' resistance and minimizing heat dissipation
Implementation Method 2
using copper matrix wires for stability
Data Source
AI summary
A mechanically operating superconducting switch has two superconducting wires, a respective end of each superconducting wire being embedded in a respective block of superconducting material. A mechanical arrangement is provided for driving respective contact surfaces of the blocks into physical contact with each other, and for separating those services.