Faraday Rotator Angle Adjustment for Current Measurement
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Solution Overview
Problem
Existing electric current measuring apparatus using the Faraday effect face challenges in fully compensating for temperature-dependent characteristics of both the Faraday rotator and optical fiber, leading to significant ratio errors in measurement values, particularly in temperature ranges between -20°C and 80°C, which affects the reliability and accuracy of current measurements.
Innovation Solution
The apparatus incorporates a signal processing circuit with a Faraday rotator having a Faraday rotation angle adjustable by α° from 22.5° at 23°C, and a lead-glass optical fiber, where the Faraday rotation angle changes in a quadratic curve with temperature, allowing for compensation of temperature characteristics and reducing ratio error fluctuations to within ±0.5% across the specified temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Faraday rotator with 22.5° rotation angle is used at 23°C, then the measurement system can operate at nominal conditions, but the ratio error fluctuates significantly across the temperature range of -20°C to 80°C
Solution Approach 1:
The patent modifies the Faraday rotation angle parameter from the conventional 22.5° to a specific value (24.0°) that compensates for temperature-dependent errors. This parameter change optimizes the measurement accuracy across the operating temperature range by pre-compensating for the temperature characteristics of both the Faraday rotator and optical fiber.
Solution Approach 2:
The patent implements a feedback mechanism where the temperature characteristics of the system are measured and used to adjust the Faraday rotation angle. By analyzing the temperature-dependent error patterns and incorporating this information into the system design, the patent achieves automatic compensation for temperature variations.
2Measurement precision
If the Faraday rotation angle is adjusted to compensate for temperature characteristics, then measurement accuracy improves across temperature ranges, but the device complexity increases
Solution Approach 1:
The patent performs preliminary compensation by pre-setting the Faraday rotation angle to a specific value that accounts for temperature characteristics. This preliminary action eliminates the need for complex real-time adjustment mechanisms, achieving temperature compensation through a simple, fixed parameter setting.
Solution Approach 2:
The patent simplifies the system by changing only one critical parameter (the Faraday rotation angle) rather than implementing complex multi-parameter adjustment systems. This single parameter change achieves temperature compensation while maintaining system simplicity.
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 configuration effectively suppresses the fluctuation range of ratio errors in measurement values to ±0.5% or ±0.2% across the temperature range, enhancing the reliability and practicality of the electric current measuring apparatus for applications such as protection relays and electric energy meters.
Implementation Method 1
uses the Faraday effect, that is, uses the rotation of the polarization plane of light by the action of a magnetic field
Implementation Method 2
the Faraday rotation angle of linearly polarized light rotating by the magnetic field of the measured electric current is detected
Implementation Method 3
uses a lead-glass fiber as an optical fiber for a sensor
Implementation Method 4
a mirror is disposed at the other end of the optical fiber for a sensor... linearly polarized light incident from one end of the optical fiber for a sensor is reciprocating by the mirror
Implementation Method 5
the polarization separating unit separates linearly polarized light into polarized light components in two orthogonal directions
Implementation Method 6
A current or voltage proportional to the intensity of received light is output from each of the photodiodes as an electrical signal
Data Source
Figure 1~2
Figure 3~4
Figure 5a~5c
AI summary
Provided is an electric current measuring instrument wherein compensation for the ratio error versus temperature characteristics of optical fibers and Faraday rotators for a sensor can be made by an optical system of an electric current instrument and wherein the fluctuation range of ratio errors in outputs can be brought within a range of ±0.5%. The fluctuation range of ratio errors in measured values of electric currents outputted by a signal processing circuit is set within a range of ±0.5% over a temperature range of -20°C or more to 80°C or less by means of the following: An electric measuring instrument is constructed in such a way as to include a signal processing circuit equipped with at least a polarized light separating unit, Faraday rotators, a light source, a photoelectric conversion element, and optical fibers for a sensor. The optical fibers for the sensor are placed around the periphery of an electrical conductor through which electric current to be measured flows. Furthermore, the rotation angle of each Faraday rotator at the time when the magnetism of each Faraday rotator is saturated is set to 22.5° + α° at a temperature of 23°C, thereby changing the rotation angle of each Faraday rotator by α° from 22.5°.