Current Sensor U-Shaped Shield to Reduce Eddy-Current Loss
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Solution Overview
Problem
Current sensors suffer from deteriorated frequency characteristics due to eddy currents generated in the magnetic shielding member when a current flows through the current path.
Innovation Solution
The current sensor design includes a busbar with a magnetic detector and a U-shaped magnetic shield where the dimension of the bottom is larger than the side walls, suppressing eddy current loss by increasing the magnetic flux concentration on the bottom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic shielding member surrounds the current path to reduce external magnetic field effects, then measurement accuracy is improved, but eddy current is generated which deteriorates frequency characteristic
Solution Approach 1:
The magnetic shielding member is divided into multiple shielding sections (first shielding section, second shielding section, third shielding section) that are arranged at different positions and orientations. This segmentation allows each section to address specific magnetic field interference directions while reducing the generation of eddy currents compared to a continuous shielding structure.
Solution Approach 2:
Different shielding sections are positioned to provide localized magnetic shielding where needed most. The first shielding section surrounds the current path in a specific direction, the second shielding section is positioned to shield from another direction, and the third shielding section provides additional localized protection. This local quality approach optimizes shielding effectiveness while minimizing eddy current effects.
2Object-affected harmful factors
If a magnetic shielding member is used to suppress external magnetic field noise, then magnetic shielding effect is improved, but eddy current loss increases causing frequency characteristic deterioration
Solution Approach 1:
The continuous magnetic shielding member is segmented into multiple discrete shielding sections positioned at different locations. This segmentation interrupts the formation of large eddy current loops while maintaining magnetic shielding effectiveness in multiple directions, thereby reducing eddy current energy loss.
Solution Approach 2:
The magnetic shielding member acts as an intermediary structure that redirects external magnetic field noise away from the detection region. By using multiple shielding sections positioned strategically, the system mediates between external magnetic interference and the sensitive detection area while minimizing energy dissipation through eddy currents.
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 configuration reduces eddy current-induced frequency characteristic deterioration, enabling a current sensor with improved measurement accuracy.
Implementation Method 1
a magnetic detector capable of detecting a magnetic field generated when the current to be measured flows through the busbar
Implementation Method 2
a magnetic shield capable of suppressing external magnetic field noise applied to the magnetic detector
Implementation Method 3
an eddy current loss caused when the current to be measured flows through the busbar can be suppressed
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A current sensor 1 according to the present invention includes a busbar 11, a magnetic detector 12 capable of detecting a magnetic field generated when a current to be measured flows through the busbar 11, and a magnetic shield 13 capable of suppressing external magnetic field noise applied to the magnetic detector 12. The busbar 11 extends in an X-axis direction. The magnetic detector 12 is disposed on a Y1 side of a Y-axis direction perpendicular to a plate surface of the busbar 11 in such a way as to face the busbar 11. When viewed in the X-axis direction, the magnetic shield 13 has a U-shape including a bottom 131 that is disposed on a Y2 side of the Y-axis direction in such a way as to face the busbar 11 and that extends in a Z-axis direction and side walls 132 extending from both ends of the bottom 131 in the Z-axis direction to the Y1 side of the Y-axis direction. The busbar 11 is disposed between the pair of side walls 132. A first dimension T1 of the bottom 131 is larger than a second dimension T2 of the side walls 132. As a result, deterioration of a frequency characteristic of the magnetic shield due to eddy current generated when the current to be measured flows is reduced.