Metal-Plate AC Current Sensor for Skin-Effect Compensation
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Solution Overview
Problem
Existing current sensors struggle to accurately measure AC currents with frequencies up to 1500 Hz or 2000 Hz due to sensitivity to mounting tolerances and temperature variations, and require complex spectral analysis to correct for skin effect-induced errors.
Innovation Solution
A current sensor system with a U-shaped magnetic shielding and a metal plate or layer positioned at a specific distance and thickness to create a superimposed magnetic field, allowing accurate measurement of AC currents without spectral analysis, using a magnetic sensor to determine the magnetic field component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnetic sensor is used to measure AC current, then galvanic separation and compact size are achieved, but measurement accuracy deteriorates at frequencies above 50 Hz due to skin effect
Solution Approach 1:
A metal plate is introduced as an intermediary element between the conductor and the magnetic sensor. This metal plate generates eddy currents that create a compensating magnetic field, thereby mediating the interaction between the high-frequency current and the sensor to improve measurement accuracy while maintaining galvanic separation
Solution Approach 2:
The skin effect, which normally causes measurement errors at high frequencies, is converted into a beneficial effect. The metal plate utilizes the skin effect to generate eddy currents that compensate for the measurement errors, turning the harmful skin effect into a useful compensation mechanism
2Measurement precision
If spectral analysis is performed to correct skin effect errors, then measurement accuracy improves, but device complexity and processing time increase
Solution Approach 1:
Instead of using complex spectral analysis to correct errors, the patent converts the skin effect into a beneficial compensation mechanism. The metal plate generates eddy currents that naturally compensate for skin effect errors, eliminating the need for complex processing while improving accuracy
Solution Approach 2:
The metal plate automatically compensates for skin effect errors through eddy current generation, making the system self-correcting without requiring external processing or control mechanisms
3Reliability
If measurement circuit is electrically isolated from load, then safety and interference reduction are improved, but current measurement accuracy deteriorates due to mounting tolerances
Solution Approach 1:
The metal plate serves as an intermediary that couples the magnetic field from the conductor to the sensor while maintaining electrical isolation. This intermediary structure compensates for mounting tolerances by providing a stable magnetic field path that is less sensitive to positional variations
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 system provides accurate measurement of AC currents with frequencies up to 1500 Hz or 2000 Hz, reducing amplitude variation errors to less than ±1.5% and eliminating the need for complex processing, while being less sensitive to mounting tolerances and temperature variations.
Implementation Method 1
an electrical conductor portion extending in a first direction and configured for conducting said AC electrical current, thereby creating a first magnetic field
Implementation Method 2
a metal plate or metal layer arranged at a predefined distance from the shielding legs portions for allowing eddy currents to flow in said metal plate or metal layer, thereby creating a second magnetic field which is superimposed with the first magnetic field
Data Source
AI summary
A current sensor system for measuring an AC electrical current, includes: an electrical conductor portion for conducting the AC current and generating a first magnetic field; a U-shaped magnetic shielding partially surrounding said electrical conductor portion, and having a central shielding portion and two shielding leg portions; a metal plate or a metal layer arranged at a distance from the shielding legs portions for allowing eddy currents to flow and for generating a second magnetic field; a magnetic sensor device arranged between the conductor portion and the metal plate or metal layer, and between the shielding leg portions, configured for measuring a magnetic field component. The sensor system likewise includes a three-phase current sensor system.