Magnetostrictive Current Sensor Flux Concentration
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Solution Overview
Problem
Current sensing technologies face challenges such as low signal strength, noise, nonlinearity, temperature dependence, and complexity, particularly in achieving high accuracy and galvanic isolation for both AC and DC measurements across a wide temperature range, with existing magnetostrictive solutions struggling to induce sufficient strain in magnetostrictive elements for effective current measurement.
Innovation Solution
A magnetostrictive current sensor design featuring a gapped magnetic core with strategically configured mounting sections and a large magnetostrictive element, coupled with a strain gauge, to enhance magnetic flux density and induce proportional strain, ensuring increased signal strength and temperature independence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetostrictive element is placed adjacent to a current carrying conduit to induce strain, then current measurement capability is achieved, but the induced strain is extremely small making measurement difficult
Solution Approach 1:
The patent transitions from direct strain measurement to measuring the magnetic field dimension indirectly. By placing the magnetostrictive element within a magnetic core that concentrates flux, the system measures magnetic field strength which correlates to current, avoiding direct measurement of the extremely small mechanical strain.
Solution Approach 2:
The magnetic core acts as an intermediary between the current carrying conduit and the magnetostrictive element. The core concentrates and directs magnetic flux through the magnetostrictive material, amplifying the magnetic field effect without requiring direct contact between the conductor and sensor elements.
2Measurement precision
If piezoelectric material is coupled to magnetostrictive element to convert strain to voltage, then electrical signal is generated, but the already small signal is substantially reduced to negligible levels
Solution Approach 1:
The patent replaces the mechanical strain-to-voltage conversion system (magnetostrictive-piezoelectric coupling) with a direct magnetic field sensing approach. The magnetostrictive element's magnetic properties are exploited to detect field strength changes, eliminating the mechanical coupling losses inherent in piezoelectric transduction.
3Measurement precision
If existing magnetostrictive sensor designs are used, then current sensing is achieved, but they fail to induce sufficient strain per ampere for effective measurement
Solution Approach 1:
The patent optimizes key parameters including the magnetostrictive element dimensions (length, width, thickness), magnetic core geometry, and material selection to maximize magnetic flux density and magnetostrictive effect. These parameter adjustments significantly increase the strain induced per ampere of current without fundamentally changing the sensor architecture.
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 solution provides a significant increase in resistance output per ampere of current flow, ensuring accurate and temperature-independent measurements of both AC and DC currents with minimal signal loss, addressing the limitations of existing technologies.
Implementation Method 1
the material will change shape when subjected to a magnetic field. Such materials include Terfenol and Gaffenol. By placing a magnetostrictive element adjacent to a current carrying conduit the magnetic field caused by the flow of current will interact with the magnetostrictive material as to induce a strain
Implementation Method 2
A piezoelectric element 3 is attached to one side of magnetostrictive element 2. When current 19 flows, Maxwell's equations state that it will induce a magnetic field which will cause an axial strain to occur in the magnetostrictive material 2. This strain is then transferred to the coupled piezoelectric element that, being piezoelectric, creates an electric potential.
Implementation Method 3
A magnetostrictive current sensor that includes a magnetic core configured to surround a current carrying conductor. The magnetic core includes a gap disposed between first and second mounting sections
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A non-contact, current sensor includes a gapped magnetic core configured to circumscribe a current carrying conductor. A magnetostrictive element is mechanically coupled to the gapped magnetic core. Current flowing in the current carrying conductor induces a magnetic field in the magnetic core that flows through the magnetostrictive element. The gapped magnetic core is provided with mounting sections to which the magnetostrictive element is mechanically coupled. The mounting sections have a geometry that increases magnetic flux in the magnetostrictive element. A strain gauge is mechanically coupled to the magnetostrictive element to measure displacement in the element induced by the magnetic flux.