Current Transformer Shielding Coils Mitigate Core Saturation
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Solution Overview
Problem
Current transformers with toroidal cores suffer from local core saturation due to external magnetic fields and misalignment, leading to inaccuracies in measurements.
Innovation Solution
A current transformer design featuring an even number of shielding coils wound around a toroidal core, with each pair connected in parallel and opposite magnetic flux directions, and the couples connected in series, to mitigate local core saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single continuous winding is used around the toroidal core, then the device structure is simple, but local core saturation occurs due to external magnetic fields and misalignment
Solution Approach 1:
The continuous winding is divided into multiple discrete winding sections arranged around the toroidal core. Each section is positioned at specific angular intervals (e.g., 90 degrees apart) to provide distributed magnetic shielding. This segmentation allows each section to independently counteract local magnetic field variations without requiring a complex continuous structure.
Solution Approach 2:
Different winding sections are configured with specific turn counts and winding directions tailored to their local positions on the core. Sections experiencing greater magnetic field interference or misalignment effects are given higher turn counts or optimized winding patterns, creating non-uniform local characteristics that address specific local saturation problems while maintaining overall system simplicity.
2Measurement precision
If shielding coils are added to reduce local core saturation, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The winding sections serve dual functions: they act as both the measurement winding and the shielding mechanism. By configuring multiple sections with appropriate turn counts and winding directions, the same structural elements that detect current also provide magnetic shielding, eliminating the need for separate shielding coils and reducing overall device complexity.
Solution Approach 2:
The measurement function and shielding function are merged into a single integrated winding structure. The multiple winding sections are electrically connected to form the secondary winding while simultaneously providing magnetic shielding through their distributed arrangement and opposite winding directions, combining two functions into one structure.
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 design effectively reduces or eliminates local core saturation, enhancing the accuracy and reliability of current transformer measurements by compensating for external magnetic influences and misalignment.
Implementation Method 1
an even number of shielding coils which are wound around said toroidal magnetic core, wherein said shielding coils are arranged two by two in order to form corresponding couples and the two shielding coils of each couple are wound on opposite parts of the toroidal magnetic core, the shielding coils in each couple being connected in parallel to establish a respective magnetic flux in each coil
Data Source
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AI summary
A current transformer (1) comprising a toroidal magnetic core (5) around which there is wound an even number of shielding coils (21, 22, 23, 24). The shielding coils (21, 22, 23, 24) are arranged two by two in order to form corresponding couples (31, 32) and the two shielding coils of each couple are wound on opposite parts of the toroidal magnetic core (5). The shielding coils (21-22, 23-24) in each couple (31, 32) are connected in parallel to establish a respective magnetic flux in each coil, wherein the magnetic flux in a first shielding coil (21, 23) of each couple (31, 32,) has an opposite direction with respect to the magnetic flux in a second shielding coil (22, 24) of each couple (31, 32), and the couples are connected in series.