Electro-optic Current Sensor with Magnetic Concentrator
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Solution Overview
Problem
Existing optical current sensors for current carrying cables are cumbersome, expensive, and difficult to install without disrupting the cable's operation, and they often struggle with sensitivity to unwanted magnetic fields and temperature sensitivity.
Innovation Solution
An optical sensor assembly with a magnetic concentrator that creates a controlled magnetic field around the cable, using a polarizing beam splitter with materials of varying Verdet constants to reduce interference from extraneous fields and a compact design that includes a zero-order waveplate for enhanced sensitivity and accuracy.
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 cable opening
Solution Approach 1:
The sensor is divided into separate modular components: a magnetic concentrator assembly that can be independently installed around the current carrying cable, and an optical sensor assembly that detects the concentrated magnetic field. This segmentation allows the magnetic concentrator to be installed without opening the cable, while the optical sensor processes the concentrated field signal.
Solution Approach 2:
A magnetic concentrator serves as an intermediary device between the current carrying cable and the optical sensor. The concentrator concentrates the magnetic field generated by the cable into a localized region where the optical sensor can detect it, enabling non-intrusive installation while maintaining measurement capability.
2Ease of operation
If bulk optical sensors with magnetic concentrator in airgap are used, then installation is simplified, but temperature sensitivity increases
Solution Approach 1:
The patent modifies the physical parameters of the optical sensor system by introducing a magnetic concentrator with a specific airgap dimension. This airgap parameter is optimized to reduce the coupling between temperature variations and sensor output, thereby reducing temperature sensitivity while maintaining installation simplicity.
3Difficulty of detecting and measuring
If garnet crystal is used in current sensor, then sensing capability is achieved, but temperature sensitivity increases
Solution Approach 1:
The patent changes the material parameter by selecting a magnetic concentrator material with specific magnetic properties and optimizing the airgap dimension. This parameter optimization reduces the temperature coefficient of the sensing system while preserving the garnet crystal's ability to detect magnetic fields through the Faraday effect.
4Device complexity
If sensor samples only one locality for short distance, then device complexity is reduced, but measurement accuracy decreases
Solution Approach 1:
The patent extends the sensing approach from a single-point measurement to a distributed measurement along the cable length. The magnetic concentrator is designed with an extended structure that samples the magnetic field over a longer distance and multiple localities, thereby improving measurement accuracy while maintaining relatively simple device architecture.
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
Enables accurate, compact, and cost-effective measurement of current across a wide dynamic range without disturbing the cable's operation, while minimizing sensitivity to unwanted magnetic fields and temperature variations.
Implementation Method 1
a magnetic concentrator that creates a controlled magnetic field around the cable
Implementation Method 2
using a polarizing beam splitter with materials of varying Verdet constants to reduce interference from extraneous fields
Implementation Method 3
a compact design that includes a zero-order waveplate for enhanced sensitivity and accuracy
Data Source
AI summary
An optical sensor that senses current by directing polarized light across an airgap that is orthogonal to a direction of current running through a conductor. The sensor includes a prism having a high Verdet constant for high sensitivity to magnetic fields, which cause an angle of polarization of the polarized light to be rotated as an indication of the magnitude of current. A polarizing beamsplitter having a low Verdet constant is mounted to the prism so that incoming light that is traveling in a direction orthogonal to the magnetic field being sensed across the airgap is insensitive to unwanted magnetic fields produced by nearby conductors. The distance the light travels in this orthogonal direction is minimized, reducing the overall volume of the sensor, making a compact sensor highly sensitive to magnetic fields of interest, largely insensitive to unwanted magnetic fields, and having a very high dynamic range for sensing current.