Current Transformer Stamped Bridge for Thermal Stability
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Solution Overview
Problem
Existing current transformers for electronic electricity meters face issues with temperature-induced resistance ratio changes due to material differences in resistors, leading to measurement errors, and require complex assembly processes.
Innovation Solution
A current transformer design featuring stamped parts with differently wide bridging sections, a separate diagonal branch made of the same material for thermal stability, and a simple assembly process, allowing for precise resistance values and a space-saving configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If adjustable resistors are used as voltage dividers for bridge branches, then fine adjustment capability is improved, but measurement precision deteriorates due to material differences causing resistance ratio changes with temperature
Solution Approach 1:
The invention extracts the adjustment capability from separate adjustable resistors and integrates it directly into the stamping structure itself. The stamping is designed with geometric features that provide inherent adjustability while maintaining thermal stability, eliminating the need for externally mounted adjustable resistors that cause measurement errors.
Solution Approach 2:
The stamping structure incorporates locally varied geometries with different widths in different sections. This creates zones with different resistance characteristics within a single homogeneous material, allowing fine adjustment of resistance ratios while maintaining thermal stability throughout the entire structure.
2Manufacturing precision
If a complex assembly process is used to achieve precise resistance values, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The current divider is segmented into distinct geometric sections (wide sections and narrow sections) within a single stamping. This segmentation allows precise control of resistance values through geometric design rather than complex assembly, simplifying the overall device structure while maintaining manufacturing precision.
Solution Approach 2:
The invention changes the geometric parameters of the stamping (widths of different sections) to achieve precise resistance values. By varying the width parameters in different sections of the stamping, the desired resistance ratios are obtained without complex assembly procedures.
3Ease of manufacture
If resistors of different materials are used to achieve desired resistance ratios, then ease of manufacture is improved, but reliability deteriorates due to thermal detuning
Solution Approach 1:
The invention uses a homogeneous material for the entire current divider stamping, eliminating thermal detuning caused by material differences. The uniform material ensures consistent thermal expansion and resistance characteristics across all sections, maintaining reliable resistance ratios under temperature variations.
Solution Approach 2:
While the material is homogeneous, the geometric structure is asymmetric with different section widths. This asymmetry achieves the desired resistance ratios through geometric variation rather than material variation, combining ease of manufacture with thermal stability.
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 design ensures geometrically precise resistance values, prevents thermal detuning, facilitates easy and potentially automated assembly, and maintains long-term stability of the resistance network.
Implementation Method 1
a separate diagonal branch is made of the same material as the stamping and is welded at its ends to junctions of a wide section and a narrow section... the separate diagonal branch preventing thermal 'detuning' of the current divider due to the same material as that of the stamped part
Implementation Method 2
the surface of the punched part and the diagonal branch is provided with an oxidation-preventing surface. This can e.g. B. by tinning, painting, passivation, etc. be achieved
Data Source
AI summary
The converter (10) has a current divider (18) formed as a Wheatstone bridge, where resistors of bridge branches are formed by sections of a flat punched part. A toroid with a secondary winding (12) of the converter surrounds separate diagonal branches (16) of the bridge. The sections of the flat punched part exhibit different widths, and the diagonal branches are formed from the same material as the flat punched part. Ends of the diagonal branches are welded to both junctions of wide- and narrow sections.