Ring-Shaped Current Sensor With Shield Gap
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Solution Overview
Problem
Current sensors with closed magnetic circuits experience magnetic saturation and loss of detection sensitivity at high current levels due to increased magnetoresistance at parts with the negative feedback coil and Hall element, leading to non-linear detection.
Innovation Solution
A current sensor with a ring-shaped magnetic core and a shield member that forms a gap to increase magnetoresistance, reducing magnetic saturation and maintaining linearity by covering the magnetic core, magneto-electric converter, and coil, and using a doubly shielded construction to minimize external magnetic field effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a closed magnetic circuit is constructed with a magnetic core to improve magnetic flux containment, then magnetic flux leakage is reduced, but magnetoresistance increases at parts with the negative feedback coil and Hall element, causing magnetic saturation and loss of detection sensitivity at high current levels
Solution Approach 1:
The magnetic core is divided into multiple segments (first magnetic core and second magnetic core) that can be assembled around the measured conductor. This segmentation allows insertion of non-magnetic components (negative feedback coil, Hall element) between the segments without creating continuous high-permeability paths that would cause saturation, while still maintaining effective magnetic flux containment through the assembled structure.
Solution Approach 2:
A non-magnetic support structure or insulating material is introduced as an intermediary between the magnetic core segments and the negative feedback coil/Hall element assembly. This intermediary prevents direct magnetic coupling that would create low-reluctance paths through the coil and sensor, thereby reducing magnetoresistance and preventing saturation while allowing the closed magnetic circuit to function.
2Object-affected harmful factors
If the magnetic shield case is used to shut out external magnetic fields, then external noise is reduced, but induced magnetic flux in the shield case causes magnetic saturation, which peaks the magnetic flux quantity and increases detection sensitivity non-linearly
Solution Approach 1:
The magnetic shield case is extracted or removed from the design, replacing it with a non-magnetic shield or no shield at all. This eliminates the problem of induced magnetic flux saturation in the shield case while still allowing external field rejection to be achieved through other means (such as differential measurement techniques or positioning the Hall element in a location where external fields are naturally minimized).
Solution Approach 2:
Instead of using a permanent magnetic shield case that saturates, a non-magnetic material shield or no shield is used. The system accepts that external fields may be present but compensates through the zero-flux measurement principle and negative feedback mechanism, which inherently reject common-mode external field interference without relying on magnetic shielding that would saturate.
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 linearity and accuracy in current detection across a wide range of currents, reducing measurement errors and external field interference, ensuring stable sensitivity and high precision.
Implementation Method 1
a magneto-electric converter that detects magnetic flux inside the magnetic core CR and outputs an electrical signal with an amplitude in keeping with a quantity of the magnetic flux
Implementation Method 2
a coil that is formed on the magnetic core and is supplied with a negative feedback current generated based on the electrical signal
Data Source
AI summary
There is provided a ring-shaped magnetic core that forms a closed magnetic circuit that encloses a measured electrical path, a magneto-electric converter that detects magnetic flux inside the magnetic core and outputs an electrical signal with an amplitude in keeping with a quantity of the magnetic flux, a coil that is formed on the magnetic core and is supplied with a negative feedback current generated based on the electrical signal, and an internal shield member disposed at least in a vicinity of the magneto-electric converter and the coil. A first gap that increases a magnetoresistance of a closed magnetic circuit, which is a closed magnetic circuit for leakage flux that leaks from the magnetic core and includes the internal shield member, a part of the magnetic core where the coil is formed, and the magneto-electric converter, is formed in the internal shield member.