Segmented Shield Current Sensor for Eddy Current Suppression
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Solution Overview
Problem
Current sensors for three-phase AC face issues with high-speed responsiveness and reliability due to eddy current generation and magnetic saturation, leading to phase delay and magnetic interference, especially in high-frequency large currents.
Innovation Solution
A current sensor design featuring a housing with a substrate and magnetic detection elements, accompanied by a pair of shields on both sides of each magnetic detection element, with flat portions extending perpendicularly to cover the current path, maintaining a predetermined interval between the shields' end portions to suppress eddy currents and magnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shield completely covers the current path from the back side, then magnetic distortion is suppressed and reliability is improved, but eddy current is generated causing phase delay and high-speed responsiveness is lowered
Solution Approach 1:
The shield is divided into multiple shield portions (first shield portion, second shield portion, third shield portion) that are spatially separated. The first and second shield portions are disposed at different positions relative to the current path, with the third shield portion connecting them. This segmentation prevents the formation of continuous eddy current paths while maintaining magnetic shielding effectiveness, thereby suppressing both magnetic distortion and eddy current generation.
Solution Approach 2:
Different portions of the shield are strategically positioned to provide localized shielding functions. The first shield portion shields the front side of the current path, the second shield portion shields the back side, and the third shield portion connects them while being positioned to minimize eddy current generation. This local quality approach allows each region to perform its specific shielding function without creating continuous eddy current paths.
2Reliability
If the shield completely surrounds the current path, then magnetic distortion is suppressed, but magnetic saturation occurs in high frequency large currents breaking the linear relationship
Solution Approach 1:
The shield is segmented into multiple portions positioned at different locations rather than forming a complete continuous surround. This segmentation reduces the total magnetic flux concentration and prevents magnetic saturation in the shield material during high frequency large current operation, thereby maintaining the linear relationship between current and detected magnetic flux density.
Solution Approach 2:
The segmented shield structure acts as an intermediary that provides sufficient magnetic shielding to suppress distortion while avoiding the magnetic saturation problem of a complete surround shield. The third shield portion serving as a connector while being positioned to minimize eddy current generation also helps in maintaining linear response characteristics.
3Speed
If the magnetic detection element is shifted from the center to improve response characteristic, then low peak value current detection is improved, but magnetic interference from adjacent phase current path occurs
Solution Approach 1:
The shield is divided into multiple portions that create distinct shielding zones. The first shield portion is disposed between the magnetic detection element and the current path front side, the second shield portion is disposed at the back side, and the third shield portion connects them. This segmentation creates effective magnetic shielding that isolates the magnetic detection element from adjacent phase current paths, preventing magnetic interference while maintaining good response characteristics.
Solution Approach 2:
The segmented shield portions act as intermediary barriers between the magnetic detection element and adjacent phase current paths. The first and second shield portions positioned at different locations create multiple barriers that effectively block magnetic interference from adjacent phases while allowing the magnetic detection element to detect the current path magnetic field accurately.
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 design enhances high-speed responsiveness, reduces phase delay, and minimizes magnetic interference between phase current paths, improving the accuracy and reliability of current detection while maintaining a linear relationship between current and magnetic flux density.
Implementation Method 1
The current is measured by detecting the magnetic strength using a magnetic detection element 400 mounted on a substrate 300 attached to the housing 200 and outputting electric power corresponding to the magnetic strength
Implementation Method 2
there is a disadvantage that the eddy current is generated by the current flowing through the current path 600
Data Source
AI summary
A current sensor to be provided in a current path through which current flows includes a housing, a substrate accommodated in the housing, a plurality of magnetic detection elements mounted on the substrate, and a pair of shields respectively disposed on both sides of each magnetic detection element. The shields are accommodated in the housing so as to surround the current path on both sides of the current path and the shields are held so that respective end portions of the shields have a predetermined interval. The magnetic detection elements and the shields are disposed in each phase current path for three-phase AC.