Current Sensor Shielding with Slit Conductive Plate
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Solution Overview
Problem
Current sensors with magnetic shielding plates face detection errors due to eddy currents generated at high frequencies, especially when measuring large currents, as non-conductive magnetic materials reach magnetic saturation and lose shielding functionality.
Innovation Solution
A current sensor design incorporating a pair of shield plates, one conductive and one non-conductive, with a slit in the conductive plate to reduce eddy current effects, and positioning the magnetic sensing element to overlap the slit but not the conductive plate, maintaining shielding functionality and preventing detection errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a non-conductive magnetic material is used for the shield plate, then eddy current effects are reduced, but the shield plate reaches magnetic saturation at large currents and loses shielding function
Solution Approach 1:
The shield plate is divided into multiple segments separated by non-magnetic gaps. This segmentation interrupts eddy current paths while maintaining magnetic shielding capability through the distributed magnetic material segments, resolving the contradiction between reducing eddy currents and maintaining shielding function at large currents.
Solution Approach 2:
Different regions of the shield plate have different properties: magnetic material regions provide shielding function while non-magnetic gap regions interrupt eddy currents. This local differentiation allows the shield plate to simultaneously reduce eddy current effects and maintain shielding capability under large current conditions.
2Reliability
If a conductive magnetic material is used for the shield plate, then shielding function is maintained at large currents, but eddy currents are generated at high frequencies causing detection errors
Solution Approach 1:
The conductive magnetic material shield plate is segmented into multiple sections with non-magnetic gaps between them. This segmentation breaks the continuous conductive path, preventing large eddy currents from forming while preserving the magnetic shielding function through the distributed magnetic material segments.
Solution Approach 2:
The shield plate structure alternates between conductive magnetic material regions (providing shielding) and non-magnetic gap regions (interrupting eddy currents). This local quality differentiation enables the plate to maintain shielding function at large currents while minimizing eddy current effects at high frequencies.
3Measurement precision
If the magnetic sensing element is positioned close to the busbar for accurate detection, then detection precision improves, but the sensing element is more affected by external magnetic fields
Solution Approach 1:
The magnetic sensing element is extracted from the direct vicinity of the busbar and positioned at a distance where the measurement precision is still sufficient. The shield plate is then used to block external magnetic fields from reaching the sensing element, allowing accurate detection while reducing external field interference.
Solution Approach 2:
The shield plate acts as an intermediary between external magnetic fields and the magnetic sensing element. It blocks external magnetic fields from directly affecting the sensing element while allowing the sensing element to detect the magnetic field generated by the busbar, thus protecting the sensing element while maintaining detection accuracy.
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 solution effectively maintains shielding even at high currents and reduces detection errors by minimizing eddy current impacts, allowing for accurate magnetic field detection with simpler frequency characteristics.
Implementation Method 1
an eddy current may be generated in the shield plate when the frequency of a measured electric current increases so that a detection error occurs due to the effect of the magnetic field generated by the eddy current
Implementation Method 2
a magnetic sensing element for detecting intensity of a magnetic field generated by the current flowing through the busbar
Implementation Method 3
a pair of shield plates that comprise magnetic materials and are arranged to sandwich the busbar in a thickness direction of the busbar
Implementation Method 4
non-conductive magnetic materials have a lower saturation magnetic flux density than conductive magnetic materials. Thus, if the measured electric current is large and the intensity of a magnetic field generated by the electric current is high, the shield plate formed of the non-conductive magnetic material may reach the magnetic saturation and lose the shielding function
Data Source
AI summary
A current sensor includes a busbar carrying an electric current to be measured, a magnetic sensing element for detecting intensity of a magnetic field generated by the current flowing through the busbar, and a pair of shield plates that include magnetic materials and are arranged to sandwich the busbar in a thickness direction of the busbar. The shield plates include a conductive shield plate including a conductive magnetic material and a non-conductive shield plate including a non-conductive magnetic material. The conductive shield plate includes a slit penetrating therethrough. The magnetic sensing element is arranged at a position where the magnetic sensing element overlaps the slits in the thickness direction and does not overlap the conductive shield plate in the thickness direction.