Segmented Magnetic Core for Current Sensor Eddy Current Reduction
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Solution Overview
Problem
Current sensors with magnetic cores face reduced detection accuracy when measuring alternating currents due to macroscopic eddy currents, which distort the magnetic flux and lead to increased magnetic saturation and demagnetizing fields.
Innovation Solution
A current sensor design featuring a magnetic field concentrating core with alternating layers of first and second magnetic materials, stacked perpendicular to the current flow, and separated by clearances or insulators, which reduces eddy currents and maintains magnetic flux distribution, thereby enhancing detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the cross sectional area of the core is enlarged to restrict magnetic saturation, then the magnetic saturation is restricted, but the macroscopic eddy current increases and detection accuracy is reduced
Solution Approach 1:
The core is divided into multiple thin magnetic material layers stacked in the flow direction of the magnetic flux. This segmentation reduces the cross-sectional area of each individual layer, thereby suppressing macroscopic eddy currents while maintaining sufficient total magnetic flux capacity to avoid saturation. The layered structure allows the core to handle large currents without saturation while keeping eddy current losses minimal in each thin layer.
Solution Approach 2:
Different regions of the core have different properties - the magnetic material layers are made thin in the cross-sectional direction to suppress eddy currents, while the stacked arrangement maintains adequate total area for magnetic flux. The gap region is specifically designed to position the magnetic sensor where the magnetic flux density is optimized for detection.
2Reliability
If the cross sectional shape is enlarged to restrict magnetic saturation, then the magnetic saturation is restricted, but the demagnetizing field increases and magnetic flux density decreases
Solution Approach 1:
The core cross-section is segmented into multiple thin layers stacked along the magnetic flux flow direction. This maintains a compact overall shape that minimizes demagnetizing fields while providing sufficient total magnetic flux capacity. Each thin layer has reduced cross-sectional area that suppresses eddy currents, and the stacked configuration accumulates sufficient magnetic flux without requiring a large single cross-sectional area.
3Adaptability or versatility
If alternating current flows in the current path, then the measurement object current is detected, but eddy current generates a magnetic field that cancels the first magnetic flux and reduces detection accuracy
Solution Approach 1:
The magnetic core is constructed from multiple thin layers of magnetic material with insulating material between them. This segmentation into thin isolated layers breaks the path for macroscopic eddy currents, suppressing the generation of canceling magnetic fields while still allowing the core to concentrate and guide the measurement magnetic flux from alternating current for accurate detection.
Solution Approach 2:
Insulating material is introduced between the magnetic material layers to serve as an intermediary that blocks eddy current paths. This insulating layer prevents the formation of large-scale eddy currents that would generate opposing magnetic fields, while the magnetic material layers continue to perform their function of concentrating and guiding the measurement magnetic flux.
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 restricts the variation of the magnetic field distribution and reduces eddy currents, maintaining the measurement object magnetic field strength and improving the detection accuracy of the current sensor.
Implementation Method 1
a magneto electric conversion element for converting an applied magnetic field to an electric signal
Implementation Method 2
a magnetic field concentrating core for concentrating a measurement object magnetic field caused by a measurement object current and for applying a concentrated measurement object magnetic field to the magneto electric conversion element
Implementation Method 3
When the alternating current flows in the current path, an eddy current for generating a magnetic field, which cancels the first magnetic flux, arises in the core
Data Source
AI summary
A current sensor includes: a magneto electric conversion element; and a magnetic field concentrating core applying a magnetic field caused by a measurement object current to the magneto electric conversion element. A planar shape of the magnetic field concentrating core perpendicular to a current flowing direction is a ring shape with a gap. The magneto electric conversion element is arranged in the gap. A part of a conductor for flowing the current is surrounded by the magnetic field concentrating core. The magnetic field concentrating core includes two first magnetic members and at least one second magnetic member, which are stacked alternately in the current flowing direction. Parts of the two first magnetic members adjacent to each other via the one second magnetic member are opposed to each other through a clearance or an insulator.