Optical Current Sensor with C-Shaped Magnetic Concentrator
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Solution Overview
Problem
Existing optical current sensors for current carrying cables are cumbersome, expensive, and lack a simple, economical design for accurate measurements across a large dynamic range without disrupting the cable's operation, and they are insensitive to unwanted magnetic fields.
Innovation Solution
An optical sensor assembly with a magnetic concentrator creating a magnetic field from the cable, combined with an electronics system for data processing, which uses a polarizing beam splitter with a high Verdet constant material to reduce extraneous electromagnetic interference and allow for compact size, enabling real-time monitoring of current and voltage across multiple cables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fiber optic cable surrounds the current carrying cable, then dynamic range is suitable, but installation is expensive and cumbersome requiring opening the cable
Solution Approach 1:
The magnetic core is divided into two separate C-shaped portions that can be independently positioned and secured to the cable. This segmentation allows the sensor to be installed by simply opening the cable access panel and attaching the components externally, eliminating the need to open the current carrying cable itself while maintaining effective magnetic field sensing across the required dynamic range.
2Stability of the object's composition
If magnetic concentrator with bulk optical sensors in airgap is used, then temperature sensitivity is stabilized, but device complexity increases
Solution Approach 1:
The optical sensing components are extracted from the complex magnetic concentrator structure and placed in a simple airgap between the two C-shaped magnetic portions. This extraction maintains the temperature stabilization benefit of the airgap while dramatically simplifying the overall device structure, allowing the use of basic bulk optical sensors without requiring complex integrated magnetic-optical assemblies.
3Adaptability or versatility
If crystal and quarter-wave plate are used for current and voltage sensing, then sensing capability is achieved, but temperature sensitivity increases and mechanical stability decreases
Solution Approach 1:
The patent uses different optical components with different temperature characteristics in different locations: the input polarizer is positioned where temperature stability is less critical, while the output polarizer and wave plate are positioned in the airgap region where temperature stabilization is most effective. This local differentiation of component placement optimizes the overall temperature sensitivity of the sensing system while maintaining full sensing capability.
4Volume of moving object
If sensor samples only one locality for short distance, then device size is reduced, but measurement accuracy decreases
Solution Approach 1:
The two C-shaped magnetic portions are positioned asymmetrically at different locations along the cable, with each portion sensing the magnetic field at its specific location. The optical system integrates these asymmetrically positioned sensing regions, allowing the compact device to effectively sample multiple localities along the cable rather than a single point, thereby maintaining measurement accuracy while keeping the device size small.
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 solution provides a compact, sensitive, and cost-effective optical sensor assembly that can accurately measure current across a wide dynamic range without disturbing the cable's operation and is insensitive to unwanted magnetic fields, enabling real-time feedback and control in electrical power distribution systems.
Implementation Method 1
a magnetic concentrator creating a magnetic field from the cable
Implementation Method 2
uses a polarizing beam splitter with a high Verdet constant material to reduce extraneous electromagnetic interference
Data Source
AI summary
An optical sensor assembly that senses current in a secondary electrical cable while sensing voltage in a primary electrical cable. The optical sensor assembly may include a sensor body, a concentrator core for measuring current. The concentrator core may be attached to a first end of the sensor body. The optical sensor assembly may include a plurality of extension arms that extend from the sensor body. The extension arms may include clamping devices on one end that are configured to attach to a first electrical cable. The concentrator core may be configured to at least partially surround a second electrical cable and sense the current from that second electrical cable.