Litz Wire Magnetic Shield for ICPT Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional magnetic shields for inductively coupled power transfer (ICPT) systems suffer from high resistive losses and overheating due to the skin effect, and lack flexibility in tailoring shielding effectiveness, which can lead to inefficient power transfer and interference between coil pairs in applications like wind turbines.
Innovation Solution
A magnetic shield formed from Litz wire conductors that undulate from the surface to distribute induced currents away from the surface, reducing effective resistance and eddy current losses, and can be shaped and loaded capacitively or inductively to optimize shielding and minimize heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid conductive plate is used for magnetic shielding, then shielding effectiveness is improved, but resistive losses and overheating increase
Solution Approach 1:
The solid conductive plate is segmented into multiple thin conductive layers separated by dielectric material. This segmentation allows eddy currents to be distributed across multiple layers rather than concentrated in a single thick plate, reducing the skin effect and resistive losses while maintaining shielding effectiveness through cumulative attenuation across layers.
Solution Approach 2:
The shield uses a composite structure combining conductive layers with dielectric material. The conductive layers provide magnetic shielding through eddy current generation, while the dielectric material provides electrical insulation between layers and structural support, creating a composite that achieves both shielding effectiveness and reduced resistive heating.
2Reliability
If a solid conductive plate is used for magnetic shielding, then shielding effectiveness is improved, but temperature increase due to overheating worsens
Solution Approach 1:
Dividing the thick conductive plate into multiple thin conductive layers separated by dielectric material reduces the skin depth within each layer, allowing eddy currents to be distributed more evenly and reducing concentrated heating. The dielectric spacers also provide thermal isolation between layers, preventing heat buildup.
Solution Approach 2:
The multi-layer structure with dielectric spacers creates a somewhat porous or distributed architecture that allows better heat dissipation compared to a solid thick plate. The gaps between conductive layers facilitate thermal management while maintaining the shielding function.
3Reliability
If better shielding is provided, then magnetic field cancellation is improved, but energy losses increase
Solution Approach 1:
Multiple thin conductive layers provide cumulative magnetic field cancellation through successive eddy current generations, achieving better shielding effectiveness than a single thick layer. The segmentation allows each layer to operate at lower current densities, reducing individual and total eddy current losses while maintaining or improving overall shielding performance.
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 use of Litz wire shields significantly reduces AC resistance and eddy current losses, enhancing power transfer efficiency and flexibility in shielding, while minimizing heating and interference between coil pairs.
Implementation Method 1
at ICPT frequencies, only the surface of the conductive plate will conduct current, due to the skin effect. This means that the effective resistance of the conductive sheet is much higher than would be measured at DC
Implementation Method 2
Time-varying magnetic fields generate eddy currents in conductive materials that act to cancel the applied magnetic fields
Implementation Method 3
Time-varying magnetic fields generate eddy currents in conductive materials that act to cancel the applied magnetic fields
Data Source
AI summary
A magnetic shield for shielding adjacent coils of an ICPT system. One or more conductors are configured to distribute induced eddy currents from the surface of the shield to below the surface and thus reduce heating due to eddy currents. The magnetic shield may be employed to transfer power over rotary couplings, such as the shaft of a wind turbine.