HTS Magnet Coil Reverse-Current Quench Dump
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Solution Overview
Problem
High temperature superconducting (HTS) magnets face challenges in rapid and uniform quench protection, particularly in large coils used for applications like tokamak plasma chambers and proton beam therapy devices, where simultaneous quenching is essential to prevent damage from temperature gradients and electromagnetic forces.
Innovation Solution
Applying a large reverse current to the magnet coil using a four-quadrant power supply, which primarily heats the radial path, ensures rapid and uniform quenching across the entire magnet, distributing the stored energy and preventing localized temperature rises.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional quench protection method is used in HTS magnets, then the quenching process can be initiated, but the temperature distribution becomes non-uniform causing localized temperature rises and potential damage
Solution Approach 1:
The coil is divided into multiple segments with independent heating elements distributed throughout the winding. Each segment can be heated independently or simultaneously, ensuring uniform temperature distribution across the entire coil during quench protection, preventing localized hot spots that could cause damage.
Solution Approach 2:
Heating elements are pre-positioned within the coil structure before operation. Upon quench detection, these elements immediately activate to counteract the rapid temperature drop by introducing controlled heat, preventing thermal runaway and ensuring uniform temperature distribution before damage can occur.
2Productivity
If the magnet current is ramped down rapidly to protect against quench damage, then the energy dump speed increases, but large electromagnetic forces and temperature gradients are generated causing structural stress
Solution Approach 1:
Heating elements are pre-installed and pre-positioned within the coil structure before operation. Upon quench detection, these elements immediately activate to counteract the rapid temperature drop caused by fast current ramp-down, preventing thermal stress and structural damage while maintaining high energy dump speed.
Solution Approach 2:
The system changes the temperature parameter by introducing controlled heating during the quench process. This counteracts the rapid cooling effect of fast current ramp-down, maintaining temperature within safe limits and preventing thermal stress while allowing rapid energy dump.
3Reliability
If insulation is added to HTS coils to prevent electrical breakdown, then the electrical insulation is improved, but the coil structure becomes more complex and the quench protection capability is reduced
Solution Approach 1:
The heating elements serve multiple functions: they provide quench protection by preventing thermal runaway, and they can also serve as temperature sensors and heating elements for normal operation. This eliminates the need for separate insulation systems, reducing overall structural complexity while maintaining electrical insulation through the inherent properties of the heating element materials.
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 effectively spreads the energy dump throughout the magnet, reducing the risk of damage from temperature gradients and electromagnetic forces, while maintaining the structural integrity of the HTS coils.
Implementation Method 1
Applying a large reverse current to the magnet coil using a four-quadrant power supply, which primarily heats the radial path
Data Source
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AI summary
An HTS magnet system comprising an HTS field coil and a power supply. The HTS field coil comprises a plurality of turns comprising HTS material and a metallic stabiliser; and an electrically conductive layer separating the turns, such that current can be shared between turns via the conductive layer. The power supply is configured to: during ramp-up of the HTS field coil, provide a first current to the HTS field coil; and during ramp-down of the HTS field coil, provide a second current to the HTS field coil opposite in direction to the first current.