Coil Device Eddy Current Interrupter Inductance Stability
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Solution Overview
Problem
In wireless power transfer systems, changes in the gap between the power transmission and reception coils can lead to unintended changes in inductance, affecting the efficiency of power transmission due to eddy current-dependent magnetic flux interactions with shields.
Innovation Solution
Incorporating an eddy current interrupter in the nonmagnetic members of the power reception coil device, such as holes or protrusions, to redirect and reduce eddy currents, thereby stabilizing the inductance across varying gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a shield larger than the power reception coil is provided to prevent magnetic flux leakage, then magnetic flux leakage is reduced, but eddy current-dependent magnetic flux is generated which cancels the magnetic flux from the power transmission coil, causing inductance to decrease
Solution Approach 1:
The shield is divided into multiple segments in the radial direction, creating gaps between adjacent segments. These gaps interrupt the eddy current paths while allowing the shield to maintain its magnetic flux containment function. The segmented structure prevents large-scale eddy currents from forming across the entire shield surface.
Solution Approach 2:
The shield has different properties in different regions: the radial direction is segmented to interrupt eddy currents, while the axial direction maintains continuity to contain magnetic flux. This local differentiation allows the shield to simultaneously prevent magnetic flux leakage and suppress eddy current effects.
2Adaptability or versatility
If the gap between power transmission and reception coils changes, then adaptability to different vehicle types and loads is improved, but the amount of magnetic flux interlinking with the shield changes, causing unintended inductance changes
Solution Approach 1:
The shield is segmented radially to create eddy current interruptions that are effective across a range of gap distances. This segmentation ensures that eddy current suppression remains consistent even as the gap between coils varies, maintaining stable inductance across different operating conditions.
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 effectively suppresses changes in inductance during power transmission and reception, maintaining optimal power transfer efficiency even when the gap between coils changes.
Implementation Method 1
eddy current-dependent magnetic flux is generated, and this magnetic flux cancels the magnetic flux from the power transmission coil
Implementation Method 2
implements wireless power transmission using magnetic coupling between coils of an electromagnetic induction scheme
Data Source
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AI summary
A first coil device includes a first coil portion that faces a second coil portion of a second coil device in a first direction and includes a conductive wire, and at least one nonmagnetic member that includes a protrusion protruding to an outside of the first coil portion in a second direction orthogonal to the first direction. The nonmagnetic member includes an eddy current interrupter that interrupts a part of an eddy current generated in the nonmagnetic member.