Balanced Multi-Filar Coil for Wireless Power Transfer
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Solution Overview
Problem
Existing wireless power transfer systems for electric vehicles face challenges in achieving balanced inductance in magnetic coils, leading to inefficiencies and potential overheating due to imbalances in current distribution across conductors, which can result in reduced reliability and faster aging of components.
Innovation Solution
The design incorporates a magnetic coil structure with a layer of magnetically-permeable material and conductors that follow convoluted paths to ensure equalized inductances by maintaining consistent proximity to the permeable layer, achieved through symmetric positioning and stacking of conductors to balance the flux paths and reduce inductive imbalance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conductors are arranged in simple parallel paths, then the coil structure is simple to manufacture, but inductance imbalance occurs leading to current distribution inefficiency
Solution Approach 1:
The coil is divided into multiple independent conductors (first conductor, second conductor, third conductor, fourth conductor) arranged in parallel, with each conductor having its own convoluted path. This segmentation allows independent optimization of each conductor's path to achieve balanced inductance while maintaining parallel structure for manufacturability
Solution Approach 2:
Each conductor is given a specific convoluted path pattern (e.g., first conductor follows path A-B-C-D, second conductor follows path A-E-F-D) that is locally optimized to achieve equal inductance. The local path configuration ensures that each conductor interacts with the magnetic core over substantially equal lengths, creating local balance that contributes to overall coil balance
2Reliability
If conductors have unequal inductance, then the coil can be manufactured with simpler paths, but current distribution becomes unbalanced causing overheating and reduced reliability
Solution Approach 1:
The conductor paths are designed to create equipotential conditions in terms of inductance - each conductor has substantially equal inductance by ensuring equal interaction length with the magnetic core. This equipotentiality of inductance values prevents current imbalance and the associated overheating issues, while the symmetric path patterns maintain manufacturing simplicity
3Productivity
If conductor paths are made convoluted to equalize inductance, then current distribution improves, but the coil structure becomes more complex
Solution Approach 1:
While the overall structure appears symmetric, the individual conductor paths use asymmetric convoluted patterns (e.g., one conductor goes through points A-B-C-D while another goes A-E-F-D) that are specifically designed to equalize inductance. This controlled asymmetry in path configuration achieves the productivity improvement through balanced current distribution without excessive structural complexity
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 approach results in a more balanced and efficient magnetic coil configuration, minimizing inductive imbalance to within 1% tolerance, enhancing the reliability and longevity of wireless power transfer systems by ensuring consistent energy transfer and reducing overheating risks.
Implementation Method 1
a layer of magnetically-permeable material and plural conductors that follow respective convoluted paths relative to the layer of magnetically-permeable material
Implementation Method 2
Wireless power transfer techniques have developed in different fields of technology, which has resulted in different terms being used to describe essentially the same element or component. Such terms as 'magnetic resonance,' 'magnetic coupling,' 'magnetic induction,' 'inductive power transfer'
Data Source
AI summary
A magnetic coil suitable for wireless power transfer comprises a layer of magnetically-permeable material and plural conductors that follow respective convoluted paths relative to the layer of magnetically-permeable material to form respective inductors. In use, the conductors have substantially equalized inductances based on the convoluted paths and interaction with the magnetically-permeable material. One way of achieving this is to place the conductors such that the overall proximity of the conductors to the layer of magnetically-permeable material along their respective lengths is substantially equal. In this way, the conductors are positioned substantially symmetrically with respect to the layer of magnetically-permeable material, such that an average distance of each individual section of the conductors proximate to the permeable layer is equal.