Grain-oriented electrical steel sheet noise reduction via laser strain
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Solution Overview
Problem
Transformer noise is generated due to magnetostrictive behavior in grain-oriented electrical steel sheets used as iron cores, particularly when these sheets have reduced iron loss properties, and existing techniques fail to effectively control the noise during stacking.
Innovation Solution
Applying linear strain to the steel sheets using a continuous laser or electron beam, with specific conditions to control the volume fraction of closure domains, thereby reducing magnetic strain and noise. The strain is applied in a direction orthogonal to the rolling direction or at a fixed angle, ensuring a magnetic flux density of 1.930 T or more and a closure domain volume fraction between 1.00% and 3.00%, which minimizes noise and maintains low iron loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If magnetic domain refining treatment is applied to reduce iron loss, then iron loss is reduced, but transformer noise increases due to magnetostrictive behavior
Solution Approach 1:
The patent applies local quality by creating non-uniform strain distribution across the steel sheet surface through selective laser or electron beam irradiation. This produces localized high-dislocation density regions that subdivide magnetic domains specifically in irradiated areas, reducing iron loss while controlling closure domain formation to manage magnetostrictive noise
Solution Approach 2:
The patent changes physical parameters by controlling the volume fraction of closure domains within a specific range (1-3%) through adjusted irradiation conditions. By modifying irradiation power, scanning speed, and beam diameter, the patent optimizes the balance between magnetic domain refinement (for low iron loss) and closure domain suppression (for low noise)
2Object-generated harmful factors
If closure domains are eliminated to reduce noise, then transformer noise is reduced, but magnetic domain structure control becomes more difficult
Solution Approach 1:
The patent applies continuous laser or electron beam irradiation across the steel sheet surface to uniformly create the desired magnetic domain structure. This continuous action ensures consistent dislocation density distribution and closure domain volume fraction control, achieving both noise reduction and precise magnetic domain structure control simultaneously
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 approach significantly reduces noise in transformers by optimizing the magnetic domain structure, achieving noise levels below 36 dBA and iron loss of 0.720 W/kg, while maintaining excellent magnetic properties.
Implementation Method 1
a technique of irradiating a steel sheet as a finished product with a laser to introduce high-dislocation density regions into a surface layer of the steel sheet
Implementation Method 2
a technique for controlling the magnetic domain width by means of electron beam irradiation
Implementation Method 3
Transformer noise is mainly caused by magnetostrictive behavior occurring when an electrical steel sheet is magnetized
Data Source
AI summary
The present invention proposes a method that can reduce the noise generated by a transformer core and the like when formed by laminations of a grain-oriented electrical steel sheet in which core loss has been reduced by a magnetic domain refinement process. In this steel sheet, linear distortion extending with an orientation in which an angle formed with a direction perpendicular to the rolling direction of the steel sheet is an angle of 30° or less is periodic in the direction of rolling of the steel sheet, core loss (W17/50) is 0.720 W/kg or less, and magnetic flux density (B8) is 1.930 T. The volume of the closure domain arising in the distortion part is 1.00-3.00% of the total magnetic domain volume within the steel sheet.