Asymmetric Shield Plates for Current Sensor Accuracy
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Solution Overview
Problem
Current sensors with magnetoelectric transducers face accuracy issues due to noise magnetic fields generated by adjacent conductors, leading to wasteful space requirements and reduced measurement accuracy when shield plates are arranged symmetrically, which can displace the symmetric axis and introduce inter-shield magnetic field components in the sensing direction.
Innovation Solution
The arrangement of shield plates is modified by giving different properties to each plate, such as varying thickness or magnetic permeability, to intentionally break line symmetry, reducing the inter-shield magnetic field component in the sensing direction, thereby improving measurement accuracy without the need for the transducer to be on the symmetric axis and minimizing wasteful space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If shield plates are arranged symmetrically to reduce noise magnetic field influence, then measurement accuracy is improved, but the symmetric axis displacement introduces inter-shield magnetic field components that reduce accuracy
Solution Approach 1:
The patent applies asymmetry by making the first and second shield plates have different magnetic permeabilities. Specifically, the shield plate closer to the magnetoelectric transducer has higher magnetic permeability than the other shield plate. This asymmetric configuration compensates for the symmetric axis displacement caused by the conductor's position, preventing inter-shield magnetic field components from affecting the transducer while maintaining noise magnetic field shielding effectiveness.
Solution Approach 2:
The patent applies local quality by varying the magnetic permeability of different shield plates according to their specific positions and functions. The shield plate closer to the transducer has higher magnetic permeability to provide stronger local shielding and compensate for axis displacement, while the other shield plate has lower magnetic permeability. This localized property differentiation optimizes the overall shielding performance and eliminates harmful magnetic field components.
2Measurement precision
If shield plates are arranged to shield the magnetoelectric transducer from noise magnetic fields, then measurement accuracy is improved, but magnetic flux flows in the shield plates generating inter-shield magnetic fields that reduce accuracy
Solution Approach 1:
The patent uses asymmetry in shield plate magnetic permeabilities to control the distribution of magnetic flux between the shield plates. By making the first shield plate have higher magnetic permeability than the second shield plate, the magnetic flux is guided preferentially through the first shield plate, reducing the generation of inter-shield magnetic fields that would otherwise affect the magnetoelectric transducer and reduce measurement accuracy.
3Measurement precision
If the magnetoelectric transducer is positioned on the symmetric axis to eliminate inter-shield magnetic field influence, then measurement accuracy is improved, but the required space between shield plates increases
Solution Approach 1:
The patent eliminates the need for symmetric axis positioning by introducing asymmetric magnetic permeability values in the shield plates. This allows the magnetoelectric transducer to be positioned closer to one of the shield plates, reducing the required space between the shield plates while still eliminating inter-shield magnetic field influence through the compensatory effect of the asymmetric permeability configuration.
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
This approach enhances the accuracy of current sensors by reducing the influence of inter-shield magnetic fields on the magnetoelectric transducer, allowing for more compact designs while maintaining high measurement precision.
Implementation Method 1
A current sensor utilizing a magnetoelectric transducer is known. The magnetoelectric transducer measures an intensity of a magnetic field generated by a current flowing in a conductor.
Implementation Method 2
As a result of the noise magnetic field being absorbed by the pair of magnetism shield plates, magnetic flux flows in the respective magnetism shield plates, and a magnetic field is generated between the pair of magnetism shield plates.
Data Source
AI summary
A current sensor is configured to measure current flowing in two bus bars aligned in an X direction and extending parallel in a Y direction. A sensing element is arranged such that its magnetism sensing direction is oriented in the X direction on a line passing through the bus bar in a Z direction. A pair of shield plates sandwiches the bus bar and the sensing element therebetween in the Z direction. The bus bar is located between the sensing element and the lower shield plate. The sensing element is located closer to the upper shield plate than to the lower shield plate. At least one of a thickness and a magnetic permeability of the magnetism shield plates is greater in the upper shield plate than in the lower shield plate.