Current Sensor U-Shaped Magnetic Shield for 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, which affects measurement accuracy.
Innovation Solution
A current sensor design with a U-shaped magnetic shield where the dimension of the bottom is larger than the side walls, reducing eddy current loss by concentrating magnetic flux density in the bottom, and optionally using stacked reference plates with insulating layers to further suppress eddy currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a magnetic shielding member surrounds the current path and magnetoelectric conversion element, then external magnetic field noise is suppressed, but eddy current is generated which deteriorates frequency characteristic
Solution Approach 1:
The magnetic shielding member is divided into a first magnetic shielding member and a second magnetic shielding member arranged in different directions. The first magnetic shielding member extends in the first direction (parallel to current flow) while the second magnetic shielding member extends in the second direction (perpendicular to current flow), creating a segmented shielding structure that reduces eddy current paths while maintaining external field rejection
Solution Approach 2:
The patent applies different shielding configurations to different spatial regions. The first magnetic shielding member provides shielding along the current flow direction where eddy currents are problematic, while the second magnetic shielding member provides shielding perpendicular to current flow where external field interference occurs, optimizing local shielding effectiveness without uniform eddy current loss
2Volume of moving object
If the magnetic shield dimensions are reduced for downsizing, then device size is reduced, but eddy current loss increases
Solution Approach 1:
By segmenting the magnetic shielding into two separate members oriented in different directions, the patent creates shorter eddy current paths in each member compared to a single large shielding structure, reducing eddy current loss while maintaining compact overall dimensions
Solution Approach 2:
The first magnetic shielding member is configured with extension in the first direction (parallel to current) that is optimized to minimize eddy current loops, while the second magnetic shielding member extends in the second direction to provide perpendicular shielding. This asymmetric configuration optimizes the balance between size and eddy current suppression
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 effectively reduces eddy current loss, maintaining or improving frequency characteristics and measurement accuracy of the current sensor.
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
the first dimension of the bottom in the second direction is larger than a second dimension of the side walls in the third direction... an eddy current loss caused when the current to be measured flows through the busbar can be suppressed
Data Source
AI summary
A current sensor includes a busbar, a magnetic detector capable of detecting a magnetic field generated when a current to be measured flows through the busbar, and a magnetic shield capable of suppressing external magnetic field noise applied to the magnetic detector. The busbar extends in an X-axis direction. The magnetic detector is disposed in such a way as to face the busbar. The magnetic shield has a U-shape including a bottom that is disposed on a Y2 side of the Y-axis direction in such a way as to face the busbar and that extends in a Z-axis direction and side walls extending from both ends of the bottom in the Z-axis direction to the Y1 side of the Y-axis direction. The busbar is disposed between the pair of side walls. A first dimension Tl of the bottom is larger than a second dimension T2 of the side walls.