Directly Coolable Multifilament Conductor Eddy Current Reduction
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Solution Overview
Problem
Magnetic coils with directly coolable multifilament conductors face challenges in efficiently managing heat dissipation and minimizing eddy currents, which can lead to heating and non-compensatable magnetic fields, especially at high frequencies used in magnetic resonance imaging applications.
Innovation Solution
A metal cooling tube with lower electrical conductivity than the surrounding conductors is used, acting as both a fluid conduit and a current-carrying filament, reducing eddy currents and enhancing cooling efficiency by minimizing thermal resistance and allowing a larger cross-sectional flow area without compromising electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a non-conductive flexible plastic or polymer tube is used for cooling, then leakage problems are avoided and fluid tightness is ensured, but the thermal resistance between the cooling means and the conductors increases, reducing cooling efficiency
Solution Approach 1:
The patent employs a composite structure where a non-conductive flexible polymer tube provides fluid tightness and mechanical protection, while metal cooling fins or heat sinks are integrated onto the tube surface to enhance thermal conduction. This composite approach combines the advantages of both materials: the polymer ensures leakage-free operation and flexibility, while the metal components maintain efficient heat transfer from the conductors to the cooling fluid.
2Productivity
If the cooling tube has a large cross section to ensure sufficient fluid flow rate, then cooling capacity is improved, but the effective conductor cross section decreases, reducing electrical conductivity
Solution Approach 1:
The conductor system is segmented into multiple parallel conductor strands surrounding the cooling tube. This segmentation allows the total electrical conductivity to be maintained across multiple smaller conductive paths, while the central cooling tube can have a larger cross-section for adequate fluid flow. The segmented structure distributes the electrical current across multiple filaments, preventing significant electrical property degradation despite the reduced individual conductor cross-sections.
Solution Approach 2:
The patent transitions from a two-dimensional cross-sectional view to a three-dimensional arrangement where conductors are positioned radially around the cooling tube in multiple layers and angular positions. This spatial distribution in three dimensions maximizes the effective conductor cross-section while accommodating a large cooling tube diameter, thereby maintaining both cooling capacity and electrical conductivity.
3Temperature
If a monolithic hollow conductor is used for direct cooling, then cooling efficiency is improved, but eddy currents increase, causing heating and magnetic field disturbances
Solution Approach 1:
The monolithic conductor is divided into multiple separate conductor filaments or strands that are arranged around the cooling tube. This segmentation interrupts the continuous conductive path that would otherwise allow large eddy currents to form, thereby reducing eddy current losses and associated heating. Each individual filament carries a portion of the total current, and the gaps between filaments act as barriers to eddy current circulation while still allowing efficient direct cooling through the central tube.
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 provides effective cooling and reduced eddy current effects, maintaining optimal magnetic field homogeneity and thermal management in magnetic resonance applications, while maintaining good electrical properties and mechanical integrity.
Implementation Method 1
the cooling tube is adapted to carry a fluid cooling means for directly cooling the conductors and for transporting the dissipated heat
Implementation Method 2
fluid cooling means flowing through the conductor means
Implementation Method 3
which are one of the natural sources for the heating of the conductor, especially when high frequencies are used
Implementation Method 4
the cooling tube is a metal conductor having a lower electrical conductivity than the conductors surrounding the tube
Implementation Method 5
the electrical dissipated power that arises in the form of heat produced when operating the magnetic coil
Data Source
AI summary
A directly coolable multifilament conductor or a magnetic coil, having at least two electric conductors and at least one cooling tube disposed between the conductors adapted to carry a fluid coolant, wherein the cooling tube is a metal conductor having a lower conductivity than the conductors surrounding the tube.