AC Current Sensor Layout Using Eddy Currents Against Skin Effect
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Solution Overview
Problem
Existing current sensors struggle to accurately measure AC currents with frequencies up to 2 kHz without requiring complex spectral analysis, especially in environments where skin effect significantly affects the magnetic field.
Innovation Solution
A current sensor system that includes an electrical conductor with a metal plate or conductive surface to induce eddy currents, which superimpose with the primary magnetic field, allowing a magnetic sensor device to determine the AC current magnitude based on the magnetic field gradient, providing improved accuracy without spectral analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spectral analysis or waveform analysis is performed to improve AC current measurement accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent extracts and compensates for the harmful skin effect separately by introducing a reference conductor that experiences the same skin effect. The magnetic sensor measures only the difference between the test conductor and reference conductor, effectively removing the skin effect component from the measurement without requiring complex spectral or waveform analysis.
Solution Approach 2:
The reference conductor acts as an intermediary element that experiences the same skin effect as the test conductor. By measuring the magnetic field difference between the two conductors, the system uses this intermediary to cancel out the harmful skin effect, achieving accurate AC current measurement without complex processing.
2Productivity
If skin effect is present in the electrical conductor, then AC current can be conducted, but measurement precision deteriorates due to distorted magnetic field
Solution Approach 1:
The patent converts the harmful skin effect into a beneficial cancellation mechanism. By introducing a reference conductor that experiences the same skin effect, the system causes the skin effect-induced magnetic field distortions to cancel each other out, transforming the harmful effect into a self-compensating mechanism that improves measurement accuracy.
Solution Approach 2:
The system changes the measurement parameter from absolute magnetic field strength to magnetic field difference between two conductors. This parameter transformation allows the skin effect, which affects both conductors equally, to cancel out in the differential measurement, thereby maintaining measurement precision despite the presence of skin effect.
3Measurement precision
If a reference conductor is added to compensate for skin effect, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent merges the reference conductor with the test conductor structure, placing them in close proximity and using the same magnetic sensor to measure both. This integration approach minimizes additional structural complexity while achieving skin effect compensation through differential measurement.
Solution Approach 2:
The magnetic sensor serves multiple functions: it measures the magnetic field of the test conductor, the reference conductor, and automatically performs differential calculation to cancel skin effect. This multi-functionality reduces the need for separate compensation circuits or complex processing systems.
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
Accurately measures AC currents with frequencies up to 2 kHz with an absolute accuracy within +/- 5% by leveraging eddy currents to compensate for the skin effect, ensuring fast and simple measurement without heavy processing.
Implementation Method 1
a metal plate or an electrically conductive surface arranged in the vicinity of said electrical conductor for allowing eddy currents to flow in said surface
Implementation Method 2
an electrical conductor configured for conducting said AC electrical current thereby creating a first magnetic field
Implementation Method 3
when AC currents flow through an electrical conductor, a phenomenon known as 'skin effect' will occur. This causes the effective electrical resistance of the electrical conductor to increase
Data Source
Figure 1(a)~1(b)
Figure 1(c)~1(d)
Figure 1(e)~1(f)
AI summary
A current sensor system for accurately measuring an AC electrical current having frequencies up to 2 kHz, the system comprising: an electrical conductor (e.g. busbar) for conducting said AC current thereby creating a first magnetic field; a magnetic sensor device for measuring a magnetic field component or gradient; an object (e.g. a metal plate) having an electrically conductive surface arranged in the vicinity of said conductor for allowing eddy currents to flow in said surface, thereby creating a second magnetic field which is superimposed with the first magnetic field; wherein the magnetic sensor device is configured for determining the current as a signal or value proportional to the measured component or gradient. The metal plate may have an opening. The current sensor system may further comprise a shielding.