Coreless Electric Current Detection with Asymmetric Sensors
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Solution Overview
Problem
Existing electric current detection devices face challenges in maintaining sensitivity and accuracy in high-frequency areas due to the influence of skin effect and external magnetic fields, particularly in complex wiring structures with adjacent phases.
Innovation Solution
A coreless-type electric current detection device is designed with a pair of magnetism detection elements arranged at asymmetric positions relative to the conductor's cross-section center, using Hall, MR, or TMR elements to detect magnetic fluxes and suppress external magnetic field interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a normal magnetic core is used in the detection device, then the device structure is simple, but the sensitivity diminishes in the high-frequency area due to iron loss
Solution Approach 1:
The patent removes the magnetic core from the detection device structure, extracting the problematic component that caused iron loss and sensitivity degradation at high frequencies. The coreless design eliminates the source of energy loss while maintaining the magnetic field detection capability through direct placement of magnetism detection elements near the conductor.
Solution Approach 2:
The patent replaces the magnetic core-based detection mechanism with a direct magnetic field sensing approach using magnetism detection elements (such as Hall elements, MR elements, or TMR elements). This substitution eliminates the need for magnetic flux conduction through a core material, thereby removing iron loss while preserving the ability to detect magnetic flux density generated by the measured current.
2Object-affected harmful factors
If magnetism detection elements are arranged symmetrically around the conductor, then the external magnetic field influence is reduced, but the sensitivity in high-frequency area diminishes due to skin effect
Solution Approach 1:
The patent employs asymmetric arrangement of magnetism detection elements relative to the conductor. Specifically, the detection elements are positioned at different radial distances from the conductor surface, with at least one element located closer to the conductor than the other. This asymmetric configuration compensates for the skin effect-induced magnetic flux concentration at high frequencies while maintaining rejection of external magnetic field interference through differential measurement.
3Area of stationary object
If bus bars in adjacent phases are located very close to each other, then the wiring structure becomes compact, but the detection device is heavily influenced by external magnetic fields
Solution Approach 1:
The patent extracts the magnetic core that would amplify external magnetic field interference, using a coreless design that directly senses magnetic flux density. This allows the detection device to operate in compact wiring arrangements with adjacent phases without being heavily influenced by external magnetic fields from neighboring conductors.
Solution Approach 2:
The asymmetric positioning of magnetism detection elements enables differential measurement that rejects common-mode external magnetic field interference from adjacent phases. By placing elements at different radial positions, the system captures the differential magnetic field signature of the target conductor while canceling out external fields that affect both elements similarly.
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 device achieves good frequency characteristics and maintains measurement accuracy in high-frequency areas by minimizing the influence of external magnetic fields and adjacent phase interference.
Implementation Method 1
a pair of magnetism detection elements for respectively detecting magnetic fluxes generated around the conductor by the electric current to be measured
Implementation Method 2
the pair of magnetism detection elements is arranged at asymmetric positions avoiding a cross-section center of the conductor and having mutually different distances from the cross-section center
Implementation Method 3
detects the electric current to be measured on the basis of detection signals obtained from the pair of magnetism detection elements
Data Source
AI summary
In some examples, an electric current detection device includes a conductor to which an electric current to be measured is applied, and a circuit unit that has at least a pair of magnetism detection elements for respectively detecting magnetic fluxes generated around the conductor by the electric current. The electric current may be detected based on detection signals obtained from the magnetism detection elements. The magnetism detection elements have a detection sensitivity relative to magnetic fluxes in a parallel orientation. Further, the magnetism detection elements are arranged at positions that are asymmetric positions that avoid a cross-section center of the conductor and that have mutually different distances from the cross-section center. Additionally, the magnetism detection elements are opposed to each other by sandwiching a line that passes through the cross-section center and which is perpendicular to a direction along which the magnetism detection elements are aligned.