Current Sensor with Segmented Ferromagnetic Core for Stray Field Rejection
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Solution Overview
Problem
Current current sensors with ferromagnetic cores struggle to accurately sense currents due to interference from stray magnetic fields, requiring multiple sensors for different current levels and increasing costs and complexity.
Innovation Solution
A current sensor design featuring a ferromagnetic core with multiple gap portions, each with distinct magnetic field sensing elements configured to generate signals that cancel out stray fields, allowing for accurate current measurement across various current levels using a single sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple magnetic field sensing elements are used to detect different current levels, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The gap in the ferromagnetic core is divided into multiple gap portions (first gap portion, second gap portion, etc.), with each gap portion containing a magnetic field sensing element. This segmentation allows different sensing elements to detect magnetic fields at different distances from the current conductor, enabling measurement of different current levels while maintaining a unified sensor structure.
Solution Approach 2:
Different gap portions are positioned at different locations relative to the current conductor, creating local variations in magnetic field sensitivity. The first gap portion is closer to the conductor for detecting higher current levels, while the second gap portion is farther away for detecting lower current levels, optimizing measurement precision for each current range.
2Device complexity
If a single sensor is used for all current levels, then device complexity is reduced, but measurement precision deteriorates due to stray magnetic fields
Solution Approach 1:
The patent converts the harmful effect of stray magnetic fields into a beneficial differential measurement approach. By positioning multiple sensing elements at different gap portions and calculating the difference between their outputs, the system eliminates stray field interference while maintaining measurement precision across all current levels using a single sensor.
Solution Approach 2:
The system uses feedback through differential calculation of magnetic field signals from multiple sensing elements. The output signal is derived by processing the difference between signals from sensing elements at different gap portions, which feedback eliminates the common-mode stray magnetic field interference and enhances measurement accuracy.
3Measurement precision
If multiple sensors are deployed to handle different current levels, then measurement precision is maintained, but manufacturing cost increases
Solution Approach 1:
The patent merges multiple sensing functions into a single integrated sensor unit. Multiple magnetic field sensing elements are incorporated into one ferromagnetic core structure with a unified gap divided into multiple portions, allowing the sensor to measure different current levels simultaneously without requiring separate sensor assemblies, thereby reducing manufacturing cost and complexity.
Solution Approach 2:
The single current sensor achieves multi-functionality by detecting multiple current levels across different ranges. The ferromagnetic core with multiple gap portions enables the same sensor to measure both high current levels (using closer gap portions) and low current levels (using farther gap portions), replacing the need for multiple specialized sensors.
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 enables precise current sensing across multiple levels with reduced susceptibility to stray magnetic fields, simplifying the design and reducing the need for multiple sensors, thereby lowering costs and complexity.
Implementation Method 1
A magnetic field generated in response to the current through the current conductor may be detected by one or more magnetic field sensing elements, such as Hall effect elements
Implementation Method 2
magnetic field sensing elements, such as Hall effect elements and/or magnetoresistance elements
Implementation Method 3
A ferromagnetic core can be used to concentrate the magnetic field for detection by the magnetic field sensing elements of the current sensor
Data Source
AI summary
A current sensor includes a ferromagnetic core having a substantially central opening for receiving a current conductor and a gap. A detector of the current sensor includes at least one first magnetic field sensing element disposed in a first gap portion and configured to generate a respective first magnetic field signal in response to a first magnetic field having a first angle with respect to the at least one first magnetic field sensing element. The detector also includes at least one second magnetic field sensing element disposed in a second gap portion and configured to generate a respective second magnetic field signal in response to a second magnetic field having a second angle with respect to the at least one second magnetic field sensing element. The first and second magnetic fields are substantially equal in magnitude and the first and second angles are substantially opposite in polarity.