Off-Center Busbar Recess for Accurate High-Frequency Current Sensing
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Solution Overview
Problem
Magnetic field sensors used to measure current strength in busbars experience systematic errors at high frequencies due to eddy currents, leading to inaccurate measurements.
Innovation Solution
A recess for the magnetic field sensor is positioned off-center in the busbar, closer to high current densities at high frequencies, maintaining a relatively constant magnetic field strength over a wider frequency range, allowing for accurate current strength calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic field sensor is positioned at the center of the busbar, then the measurement is simple and the sensor is well-protected, but the measurement accuracy deteriorates at high frequencies due to eddy currents
Solution Approach 1:
The patent applies asymmetry by deliberately positioning the magnetic field sensor off-center in the busbar. Specifically, the sensor is placed in a recess that is shifted by a predetermined distance from the geometric center of the busbar cross-section. This asymmetric positioning allows the sensor to operate in a region where the magnetic field remains relatively constant across a wide frequency range, thereby resolving the measurement accuracy deterioration caused by eddy currents in conventional central positioning.
2Power
If the busbar cross-section is increased to transport heavy currents, then the current carrying capacity improves, but the magnetic field strength at the center decreases due to eddy currents
Solution Approach 1:
The patent applies local quality by creating a specific local environment for the magnetic field sensor through an off-center recess positioning. Instead of relying on the overall busbar cross-section size to determine magnetic field strength, the sensor is placed in a localized region with specific electromagnetic characteristics. This local positioning ensures that the sensor experiences a relatively constant magnetic field strength despite variations in busbar size and frequency, thereby maintaining measurement accuracy while preserving high current carrying capacity.
3Measurement precision
If the recess is positioned closer to the edge of the busbar, then the magnetic field strength increases at high frequencies, but the sensor is more exposed to external influences
Solution Approach 1:
The patent applies preliminary action by pre-positioning the magnetic field sensor in an off-center recess during the busbar manufacturing process. This predetermined positioning, calculated based on the busbar geometry and expected frequency range, proactively compensates for eddy current effects before the busbar is put into service. The recess serves as a pre-prepared measurement zone that inherently provides both optimal magnetic field characteristics and protection from external influences.
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 extends the frequency range for accurate current measurement, reducing variations to less than 1% up to 5 kHz, compared to over 20% in conventional systems at 3 kHz, while maintaining measurement accuracy.
Implementation Method 1
the magnetic field generated by the current in the busbar can be measured
Implementation Method 2
magnetic field sensors, with the aid of which the magnetic field generated by the current in the busbar can be measured
Implementation Method 3
the current strength of eddy currents that are generated in busbars also increases. The eddy currents in turn themselves generate a magnetic field which opposes the magnetic field that is generated by the current flowing in the busbar
Implementation Method 4
eddy currents that are generated in busbars also increases. The eddy currents in turn themselves generate a magnetic field
Implementation Method 5
At relatively high frequencies, the positions of high current densities lie closer to the edge of a conductor because of the eddy currents (skin effects) occurring, so that the strength of a magnetic field there increases
Data Source
AI summary
A busbar for current transport comprises conductive material, which extends along a current direction. A recess for a magnetic field sensor extends into the conductive material, a middle of the recess being shifted by a predetermined distance from a middle of the conductive material in the direction of an edge of the conductive material, so that, within a frequency range, a frequency dependency of a magnetic field, which is induced by an alternating current flowing along the current direction, is reduced in comparison with a busbar having a central recess.