Three-Group Detection Coil for Wireless Power Foreign Metal Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing metal foreign matter detection methods in wireless power transfer systems have low efficiency, especially when the eddy current loss of the foreign matter is small compared to the system transmit power, leading to inaccurate detection and potential damage.
Innovation Solution
A detection coil system comprising three groups of coils, where the sum of induced electromotive forces from the first, second, and third groups of coils in a magnetic field is designed to be zero, allowing for accurate detection of metal foreign matter by detecting a non-zero sum when the foreign matter is present.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If power difference comparison method is used to detect metal foreign matter, then detection can be performed when eddy current loss is relatively large, but detection efficiency is low and cannot detect foreign matter with small eddy current loss
Solution Approach 1:
The detection coil is divided into three groups of coils (first, second, and third groups) that are continuously wound and coaxial. Each group contributes to the total induced electromotive force, allowing the system to detect subtle changes in magnetic field distribution caused by metal foreign matter through the cumulative effect of all three groups.
Solution Approach 2:
The patent changes the detection parameter from power difference (which requires relatively large eddy current loss) to induced electromotive force sum (which can detect even small eddy current losses). By monitoring the sum of induced electromotive forces from the three coil groups, the system can detect metal foreign matter with small eddy current losses that would be undetectable using power difference comparison.
2Measurement precision
If existing detection methods are used, then system complexity is low, but detection accuracy is insufficient especially for small eddy current loss cases
Solution Approach 1:
The detection coil is divided into three groups of coils (first, second, and third groups) that are continuously wound and coaxial. Each group contributes to the total induced electromotive force, allowing the system to detect subtle changes in magnetic field distribution caused by metal foreign matter through the cumulative effect of all three groups.
Solution Approach 2:
The three-group coil structure serves multiple functions: it detects metal foreign matter with various sizes and positions, works with the wireless power transfer system's existing magnetic field, and provides both detection capability and maintains power transfer functionality. This multi-functionality improves detection accuracy without requiring completely separate detection hardware.
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 enhances the detection efficiency and accuracy of metal foreign matter, preventing damage and ensuring reliable operation in wireless power transfer systems.
Implementation Method 1
A value of a sum of induced electromotive forces generated by the first group of coils and the third group of coils in a first magnetic field is equal to a value of an induced electromotive force generated by the second group of coils in the first magnetic field
Implementation Method 2
An eddy effect is caused to a metal in the high frequency magnetic field, to generate an induced current in the metal. However, the induced eddy current generated in the metal generates a reverse eddy current magnetic field
Data Source
AI summary
A detection coil includes a first group of coils, a second group of coils, and a third group of coils that are continuously wound and coaxial, and the second group of coils is located between the first group of coils and the third group of coils. A coil that generates the first magnetic field is coaxial with the first group of coils, the second group of coils, and the third group of coils. A sum of the induced electromotive forces of the first group of coils, the second group of coils, and the third group of coils is zero. When a metal foreign matter exists, a sum of the induced electromotive forces of the first group of coils, the second group of coils, and the third group of coils is not zero.