Wireless Charging Ferrite Layout to Reduce Circulating Flux
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Solution Overview
Problem
Current wireless charging systems for electric vehicles face challenges in managing high magnetic flux density and thermal issues in ferrite structures, leading to potential thermal failure and reduced efficiency, especially in high-power applications.
Innovation Solution
A heuristic design approach is employed to create wireless power transfer pad structures with magnetically permeable blocks spaced apart by specific inter-section spacings that reduce circulating flux while maintaining coupling, incorporating airgaps and heat transfer channels to manage thermal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If airgaps are distributed between adjacent ferrite tiles to reduce circulating flux, then circulating flux is reduced, but coupling between primary and secondary pads is reduced
Solution Approach 1:
The ferrite structure is segmented into multiple tiles with airgaps between them. The airgaps are strategically positioned to interrupt circulating flux paths while preserving coupling flux paths, thereby reducing harmful circulating flux without significantly degrading coupling efficiency
Solution Approach 2:
Different regions of the ferrite structure have different airgap configurations. Airgaps are placed selectively in regions where they interrupt circulating flux but do not block coupling flux, creating local variations in magnetic properties that optimize both flux reduction and coupling maintenance
2Productivity
If high magnetic flux density is allowed in ferrite structure to maintain coupling, then power transfer efficiency is maintained, but thermal problems and ferrite cracking increase
Solution Approach 1:
The ferrite structure is divided into multiple tiles with airgaps, which distributes the magnetic flux density more evenly across the structure. This prevents localized hotspots while maintaining overall coupling efficiency, as the flux is spread over a larger effective area
Solution Approach 2:
Airgaps act as intermediary elements that modify the magnetic flux distribution. They provide thermal relief by reducing flux density in critical regions while still allowing sufficient flux for power transfer, effectively mediating between thermal management and power transfer requirements
3Reliability
If ferrite blocks are closely spaced to maximize magnetic coupling, then coupling efficiency is improved, but circulating flux increases
Solution Approach 1:
The ferrite structure is segmented into tiles with controlled airgaps between them. This segmentation creates discrete magnetic circuits that limit the circulation of flux around the edges while maintaining strong coupling through the intended flux paths
Solution Approach 2:
The airgap configuration is asymmetrically designed with different gap sizes and positions tailored to the specific flux patterns. Larger airgaps are placed where circulating flux is most problematic, while smaller gaps or no gaps are placed where coupling flux needs to be maximized
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 proposed design effectively reduces circulating flux and thermal hotspots, achieving improved efficiency and preventing ferrite fracturing, with reduced magnetic structure temperatures from 168°C to 67°C in 30 minutes, while maintaining efficient power transfer.
Implementation Method 1
a layer comprising a plurality of magnetically permeable blocks, adjacent blocks spaced apart by an inter-block spacing, wherein at least two adjacent blocks are spaced apart by an inter-section spacing
Implementation Method 2
the inter-section spacing configured to reduce circulating flux in the layer
Data Source
AI summary
The present invention relates to magnetic structures for wireless power transfers systems. In particular the invention relates to improved magnetic and ferrite layouts as well as pad designs and methods of predicting and preventing thermal failure of high-power ferrite structures. In part it relates to a wireless power transfer pad magnetic structure comprising at least two adjacent blocks are spaced apart by an inter-section spacing configured to reduce circulating flux in the layer. In part it relates to a wireless power transfer pad magnetic structure comprising a first surface configured to locate nearer a wireless power transfer coil than a second surface wherein the relative magnetic permeability of the magnetic structure increases with distance from the first surface. In part it relates to a method of preparing a magnetically permeable block for a wireless power transfer pad, the method comprising: thermally pre-cracking the magnetically permeable block.