Three-Busbar Current Sensor With Shieldless Magnetic Field Cancellation
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Solution Overview
Problem
Existing current detection devices face complexity due to the need for magnetic shields to reduce the effect of external magnetic fields, particularly in measuring three-phase AC currents flowing through busbars.
Innovation Solution
A current sensor design that utilizes three busbars and three magnetic detection elements with parallel sensitivity axes, arranged to cancel out internal magnetic fields without the need for magnetic shields, using a processing circuit to calculate current values based on output signals from these elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic shields are used to reduce the effect of external magnetic fields, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent divides the measurement system into three separate magnetic detection elements, each responsible for detecting magnetic fields from specific busbars. This segmentation allows the system to measure three-phase currents independently without requiring magnetic shields, as each detector is positioned to sense only its designated busbar's field.
Solution Approach 2:
The patent introduces a processing circuit as an intermediary that receives signals from the three magnetic detection elements and calculates the current values. This intermediary process compensates for external magnetic field effects through mathematical processing rather than physical shielding, maintaining measurement accuracy while simplifying the hardware configuration.
2Measurement precision
If magnetic shields are used to suppress external magnetic field effects, then measurement accuracy is improved, but device size increases
Solution Approach 1:
The patent extracts the magnetic field detection function from the busbars themselves by positioning magnetic detection elements in close proximity to each busbar. This extraction allows the system to measure current effects directly without requiring additional magnetic shielding components, thereby reducing overall device size while maintaining accuracy.
Solution Approach 2:
The patent transitions from a spatial shielding approach (using magnetic shields in the physical space around busbars) to a signal processing approach (using mathematical calculations in the processing circuit). This dimensional shift from physical space to computational space eliminates the need for magnetic shields, reducing device volume while preserving measurement capability.
3Measurement precision
If magnetic shields are used to reduce external magnetic field effects, then measurement accuracy is improved, but assembly complexity increases
Solution Approach 1:
The patent merges the functions of multiple magnetic detection elements and the processing circuit into an integrated measurement system. By combining these components in a unified structure, the patent simplifies assembly compared to installing separate magnetic shields around each busbar, as the integrated design requires fewer discrete parts and simpler positioning.
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 current values in three-phase AC systems while suppressing external magnetic field effects, with a simplified configuration that reduces size, weight, and assembly complexity, maintaining high measurement accuracy and responsiveness.
Implementation Method 1
Each of the first, second and third magnetic detection elements is arranged in such a way that each of the sensitivity axes is orthogonal to a first magnetic field that is generated around the first busbar when a current flows in the first busbar
Data Source
AI summary
A current sensor is provided in which each of first, second and third magnetic detection elements are arranged such that each of sensitivity axes of the magnetic detection elements is orthogonal to a first magnetic field that is generated around a first busbar when a current flows in the first busbar. Where current values of currents flowing in the first busbar is I1, flowing in the second busbar is I2, flowing in the third busbar is I3, and output values of the first, second and third magnetic detection elements are V1, V2, and V3, respectively, and an output component caused by a uniform external magnetic field is Bex, the processing circuit calculates at least one of I1, I2, and I3 that satisfy corresponding relationships: I2∝(d−f)V1+(f−b)V2+(b−d)V3, I3∝(c−e)V1+(e−a)V2+(a−c)V3, and I1=−(I2+I3), from linear equations with three unknowns: V1=aI2+bI3+Bex, V2=cI2+dI3+Bex, and V3=eI2+fI3+Bex.