Precision Near-Field Current Transducer with Optimized Coil Turns
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Solution Overview
Problem
Rogowski coils struggle to accurately measure currents in environments with non-linear spatial gradients of magnetic fields, especially when close to external current-carrying conductors, leading to compromised magnetic field rejection and measurement errors.
Innovation Solution
The design of current transducers with conductive coils shaped to form loops, featuring notional bands and optimized turns to maintain a constant pitch and area ratio, ensuring ideal implementation of Ampere's law throughout the volume, rather than just along a line of integration, thereby enhancing magnetic field rejection and measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If Rogowski coils are used for current measurement, then the measurement can be performed with a simple coil structure, but the measurement precision deteriorates when close to external current-carrying conductors due to non-linear spatial gradients of magnetic fields
Solution Approach 1:
The patent applies local quality by varying the turn density locally within different sections of the coil. The coil is divided into multiple sections with different numbers of turns, where each section has a turn density optimized for its specific position relative to the conductor being measured. This local optimization compensates for the non-linear spatial gradients of magnetic fields in different regions, improving measurement precision without significantly increasing overall device complexity.
Solution Approach 2:
The patent segments the coil into multiple discrete sections, each with independently optimized turn counts. This segmentation allows the coil to better approximate the ideal continuous distribution of turns required by Ampere's law, particularly in regions where the magnetic field gradient is most non-linear. The segmented structure enables precise control over the magnetic flux linkage in each section.
2Volume of moving object
If Rogowski coils are positioned close to conductors for compact design, then the device size is reduced, but the magnetic field rejection capability deteriorates due to non-linear spatial gradients
Solution Approach 1:
The patent uses local quality by assigning different turn densities to different spatial sections of the coil. Sections closer to external current-carrying conductors have optimized turn counts that compensate for the stronger non-linear field gradients in those regions. This local optimization maintains magnetic field rejection capability even when the transducer is positioned compactly close to conductors.
Solution Approach 2:
The patent changes the parameter of turn density across different sections of the coil. By varying the number of turns per unit length in different sections, the coil creates a non-uniform magnetic flux linkage that counteracts the non-linear spatial gradients of external magnetic fields, thereby maintaining rejection capability in compact configurations.
3Ease of manufacture
If the coil follows a simple circular shape, then the manufacturing is easier, but the ability to reject magnetic fields from nearby external currents is compromised when the coil is not perfectly circular
Solution Approach 1:
The patent applies local quality by optimizing the turn density at specific locations along the coil path. Rather than requiring perfect circular symmetry, the invention allows for practical deviations from ideal geometry by locally adjusting the number of turns in different sections. This compensates for manufacturing tolerances and positioning variations, maintaining magnetic field rejection capability without demanding extremely precise circular shaping.
Solution Approach 2:
The patent segments the coil into multiple sections with independently optimized turn counts, which allows the overall coil shape to accommodate practical manufacturing constraints. Each segment can be independently adjusted to compensate for deviations from the ideal circular path, making the system robust to manufacturing variations while maintaining performance.
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 significantly improves immunity to nearby magnetic fields, reducing measurement errors and maintaining accuracy even in close proximity to external currents, by applying Ampere's law principles throughout the transducer's volume rather than just along a line, resulting in enhanced current measurement precision.
Implementation Method 1
a conductive loop in a changing magnetic field will have a voltage E generated across the ends of the loop proportional to the rate of change of the magnetic flux φ linking it
Implementation Method 2
When a time-varying electric current flows through a conductor a corresponding time-varying magnetic field exists in the space around it. Ampere's law states that the line integral of the magnetic flux density along any closed path equals the surface integral of the current density through the surface thus enclosed
Data Source
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AI summary
A current transducer (30) comprising a conductive coil shaped to define a plurality of turns (34) and shaped to form a loop, wherein for each turn there is a substantially constant ratio between an incrementally small portion of the area defined by the respective turn, and the effective turns' pitch at the corresponding point of a line of integration normal to the respective turn. The transducer aims to achieve an ideal implementation of Ampere's law throughout the whole volume of the transducer, rather than only along one line of integration and,as a result, exhibit improved immunity from the magnetic fields of nearby external currents.