Current Transformer Core Nanocrystallization
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Solution Overview
Problem
Current transformer cores with Fe-based nanocrystalline alloy cores face challenges in achieving high magnetic permeability while minimizing magnetic deviation and maintaining excellent temperature characteristics, which are essential for size reduction and cost-effectiveness in devices like current meters.
Innovation Solution
A manufacturing method involving the winding or layering of a soft magnetic material layer with a Fe-based nanocrystalline alloy ribbon of specific thickness, subjected to longitudinal-field heat treatment followed by transverse-field heat treatment, to achieve high magnetic permeability with reduced residual magnetic flux density and stable temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a magnetic field is applied in the magnetic path direction during crystallization heat treatment to improve magnetic permeability, then magnetic permeability increases, but residual magnetic flux density increases causing magnetic deviation
Solution Approach 1:
The patent applies a magnetic field during the crystallization heat treatment process as a preliminary action to establish favorable magnetic domain structures before the core is put into service. This preliminary magnetic field application during manufacturing ensures that the magnetic permeability is optimized while controlling residual magnetic flux density, thereby preventing magnetic deviation during actual operation.
Solution Approach 2:
The patent optimizes multiple parameters including the intensity and direction of the applied magnetic field during heat treatment, the heat treatment temperature profile, and the composition of the Fe-based nanocrystalline alloy. By carefully adjusting these parameters, the patent achieves high magnetic permeability while maintaining low residual magnetic flux density, thus resolving the contradiction between magnetic permeability improvement and magnetic deviation prevention.
2Volume of moving object
If core size is reduced to enable device miniaturization, then device size decreases, but maintaining high magnetic permeability becomes more difficult
Solution Approach 1:
The patent uses Fe-based nanocrystalline alloy with optimized composition and applies controlled heat treatment parameters to achieve high magnetic permeability in small-sized cores. The nanocrystalline structure with grain sizes in the nanometer range provides high permeability even in miniaturized cores, overcoming the typical size-permeability trade-off.
Solution Approach 2:
The patent employs Fe-based nanocrystalline alloy which is a composite material with specific microstructure (nanometer-scale crystalline grains in an amorphous matrix). This composite structure provides both high magnetic permeability and suitability for miniaturization, allowing small core sizes while maintaining excellent magnetic properties.
3Measurement precision
If magnetic permeability is increased to improve sensitivity, then sensitivity increases, but temperature stability of magnetic permeability becomes more challenging to maintain
Solution Approach 1:
The patent optimizes the composition of the Fe-based nanocrystalline alloy and the heat treatment parameters to achieve a balance between high magnetic permeability and temperature stability. By controlling the crystallization process and alloy composition, the patent minimizes the temperature coefficient of permeability, ensuring stable operation across the intended temperature range while maintaining high sensitivity.
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 method results in a current transformer core with high magnetic permeability that is resistant to magnetic deviation and exhibits excellent temperature characteristics, enabling improved sensitivity and reduced core size and cost in measurement devices.
Implementation Method 1
performing a heat treatment so as to crystallize the amorphous alloy ribbon, thereby obtaining a core which has a nanocrystalline organization
Implementation Method 2
applying a magnetic field in a magnetic path direction of the core element in the step of crystallization by a heat treatment
Implementation Method 3
the ratio of the saturation magnetic flux density Bs and the residual magnetic flux density Br (Br/Bs) is small
Data Source
Figure 1~2B
Figure 3~5
Figure 6~7
AI summary
A manufacturing method of a current transformer core includes: the step of providing a core element formed by winding or layering a Fe-based amorphous alloy ribbon whose thickness is not more than 15 µm and which can be converted into nanocrystals; a longitudinal-field heat treatment step which includes performing a heat treatment on the core element in the presence of a magnetic field of not less than 100 A/m applied in a magnetic path direction of the core element, thereby forming a core; and a transverse-field heat treatment step which includes, after the longitudinal-field heat treatment step, performing a heat treatment on the core in the presence of a magnetic field applied in a direction perpendicular to the magnetic path direction of the core, thereby forming a core. µr(25) is adjusted by the transverse-field heat treatment step to a value between 0.4×µr(max)(25) and 0.9×µr(max)(25) where µr(max)(T) is µr(T) achieved by the longitudinal-field heat treatment step, and µr(T) is an amplitude magnetic permeability of the core measured at a temperature T (°C) in the presence of an AC magnetic field of frequency f=50 Hz and amplitude H=1.0 A/m.