Current Sensing Assembly with Shielded Magnetic Joints
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Solution Overview
Problem
Existing current sensing devices face challenges in achieving high sensitivity to low currents due to interference from stray magnetic fields and high permeability materials diverting the measured magnetic field, leading to inaccuracies and reduced sensitivity.
Innovation Solution
A current sensing assembly with movable arms forming a closed magnetic circuit, equipped with magnetic field sensors at joints shielded by permeable cuffs, and an optional compensating magnetic field generation to minimize net magnetic fields at sensors, ensuring accurate measurement of currents without direct electrical contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If high permeability material arms are used to shield sensors from stray magnetic fields, then shielding effectiveness is improved, but the magnetic field generated by the current to be measured is diverted away from the sensors, reducing sensitivity
Solution Approach 1:
The magnetic circuit is segmented into two distinct parts: arms made of high permeability material for shielding, and joints made of low permeability material to prevent field diversion. This segmentation allows each part to perform its specific function without interfering with the other, resolving the contradiction between shielding effectiveness and measurement sensitivity.
Solution Approach 2:
Different parts of the magnetic circuit are assigned different material properties: the arms use high permeability material optimized for shielding, while the joints use low permeability material optimized for allowing magnetic field passage. This local differentiation of material qualities enables simultaneous achievement of shielding and sensitivity.
2Reliability
If arms are pressed together to reduce gap between end faces, then magnetic circuit continuity is improved, but manufacturing precision and assembly difficulty increase
Solution Approach 1:
The problematic requirement for precise end-face contact is extracted from the design by introducing joints as separate components. The joints provide the magnetic circuit connection without requiring precise alignment or pressing, thereby eliminating the manufacturing precision issue while maintaining magnetic circuit continuity.
Solution Approach 2:
The joints act as intermediary components between the arms, providing a controlled connection point that ensures magnetic circuit continuity without requiring precise mechanical contact between arm end faces. This intermediary solution resolves the contradiction by decoupling magnetic continuity from mechanical precision.
3Object-affected harmful factors
If variable reluctance between arm ends is reduced by improving contact, then fringe field leakage is reduced, but device complexity and assembly difficulty increase
Solution Approach 1:
The variable reluctance issue at the arm ends is extracted and relocated to the joints, which are specifically designed to control magnetic flux paths. This allows fringe field leakage to be managed through joint design rather than requiring complex assembly procedures to ensure precise arm contact.
Solution Approach 2:
The joints are designed to automatically provide the necessary magnetic circuit connection and fringe field control through their inherent structure and material properties, without requiring complex assembly procedures or external adjustment mechanisms. The joints self-regulate the magnetic flux paths to minimize fringe field leakage.
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 provides improved sensitivity to low currents by shielding sensors from external fields and preventing magnetic field diversion, resulting in precise and accurate current measurement with reduced interference.
Implementation Method 1
detection of the magnetic filed resulting from the flow of current
Implementation Method 2
acts to shield the magnetic field sensors from interference from external magnetic fields
Implementation Method 3
form a continuous loop of high permeability material to shield the sensors from magnetic interference
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A current sensing assembly has first and second arms of a magnetically permeable material arranged to enclose a cable carrying an electrical current to be sensed or measured by coming together at joints, with the arms and joints forming a magnetic circuit around the cable. At least one of the joints houses a magnetic sensor, such as a Hall-effect sensor, which is used to detect or measure the current. A cuff of a magnetically permeable material is arranged and positioned to substantially enclose the joint housing the sensor, when the arms are in place around the cable, in order to shield the first magnetic field sensor from stray magnetic fields. There may be a gap between the arms at the joint in order to prevent the field generated by the current to be measured being shunted through the arms away from the sensor and the cuff may have an aperture directed towards the cable to prevent the sensor being shielded from the field generated by the current. Devices and methods using the current sensing assembly are detailed.