Transformer Wound Core Bending With Controlled Subgrain Boundaries
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Solution Overview
Problem
The efficiency of transformer iron cores produced by bending steel sheets with a small inner radius of curvature varies due to unintentional iron loss deterioration, which is not effectively minimized by existing methods.
Innovation Solution
A wound core design featuring grain-oriented electrical steel sheets with specific chemical compositions and subgrain boundary configurations, where the existence frequency of subgrain boundaries in certain regions is controlled to minimize iron loss and maintain optimal magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If steel sheets are bent with a small inner radius of curvature (5 mm or less) to form corner portions, then the processing strain is concentrated only in the bent portion and annealing can be omitted, but unintentional iron loss deterioration occurs due to subgrain boundary effects
Solution Approach 1:
The invention applies local quality by controlling subgrain boundary characteristics specifically in regions adjacent to bent portions, while maintaining different properties in other regions. The subgrain boundary existence frequency is controlled to be 0.010 or more in planar portions adjacent to bent portions, while being 0.005 or more in bent portions themselves, creating localized property differentiation that minimizes iron loss deterioration at critical locations without compromising overall manufacturability
Solution Approach 2:
The invention changes physical parameters by controlling the inner radius of curvature of bent portions to be 5 mm or less and regulating the subgrain boundary existence frequency in specific regions. By adjusting these parameters during the bending process and material selection, the invention achieves concentration of processing strain in bent portions while preventing iron loss deterioration through controlled subgrain boundary distribution
2Productivity
If the inner radius of curvature of bent portions is reduced to concentrate strain, then annealing process can be omitted, but iron core efficiency deteriorates due to increased iron loss
Solution Approach 1:
The invention applies preliminary action by pre-controlling the subgrain boundary existence frequency in the steel sheets before bending. By ensuring that the subgrain boundary existence frequency is 0.010 or more in planar portions adjacent to bent portions and 0.005 or more in bent portions themselves, the material is prepared in advance to withstand the strain concentration from small-radius bending without subsequent annealing, thus maintaining both productivity and minimizing iron loss
Solution Approach 2:
The invention creates local quality differences by controlling subgrain boundary distribution specifically in regions adjacent to and within bent portions. This localized control allows the bent portions to concentrate strain effectively while the adjacent planar portions with higher subgrain boundary frequency prevent iron loss deterioration, enabling high productivity without iron loss penalties
Data Source
AI summary
This wound core is a wound core including a substantially rectangular wound core main body in a side view, wherein, in the wound core main body, first planar portions and corner portions are alternately continuous in a longitudinal direction, each corner portion has a curved shape in a side view of the grain-oriented electrical steel sheet, two or more bent portions having a second planar portion between the adjacent bent portions are provided, and in at least one of the first planar portion and second planar portion in the vicinity of the bent portion, the following Formula (1) is satisfied:(Nac+Nal)/Nt≥0.010 (1)here, Nt is a total number of grain boundary determination locations in the first planar portion and second planar portion region adjacent to the bent portion, and Nac and Nal each are a number of determination location at which subgrain boundaries are able to be identified in a direction parallel to and direction perpendicular to the bent portion boundary.