Polygonal Wound Core Bending With Grain Size Control
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Solution Overview
Problem
The efficiency of wound cores produced by bending steel sheets with a small radius of curvature is affected by the crystal grain size and shape of the steel sheets, leading to inefficiencies due to the combination of the iron core shape and steel sheet properties.
Innovation Solution
A wound core is formed by laminating polygonal annular grain-oriented electrical steel sheets with specific crystal grain sizes and curvature radii, where the grain-oriented electrical steel sheets have a chemical composition of Si 2.0 to 7.0% and a Goss orientation, with controlled crystal grain sizes in the bent portions to minimize efficiency deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If steel sheets are bent with a small radius of curvature (3 mm or less) to form corner portions, then the processing strain is concentrated only in the bent portion and the conventional large-scale pressing process is eliminated, but the crystal grain size in the bent portion increases and causes deterioration of iron core efficiency
Solution Approach 1:
The patent applies local quality by differentiating the crystal grain size requirements for different regions of the steel sheet. Specifically, the bent portion (corner) is allowed to have a larger crystal grain size (2W or less) compared to the planar portions, which maintain smaller grain sizes. This localized differentiation allows the bent portion to accommodate the curvature strain while the planar portions maintain optimal magnetic properties, thus resolving the contradiction between ease of manufacturing and iron core efficiency.
Solution Approach 2:
The patent employs parameter changes by controlling the crystal grain size parameter in the bent portion to be 2W or less (where W is the width of the bent portion). This specific parameter control allows the material to withstand the bending stress with small radius of curvature while maintaining acceptable magnetic properties, thereby enabling both easy manufacturing and acceptable reliability.
2Reliability
If the crystal grain size in the bent portion is reduced to improve iron core efficiency, then the magnetic properties are improved, but the processing becomes more difficult and requires additional annealing steps
Solution Approach 1:
The patent applies preliminary action by controlling the crystal grain size in the bent portion to be 2W or less before the bending process. This pre-control of grain size ensures that the material is already optimized to withstand the bending strain and maintain magnetic properties, eliminating the need for subsequent annealing processes to reduce grain size. Thus, the processing is simplified while maintaining high iron core efficiency.
3Reliability
If the radius of curvature of the bent portion is increased to reduce processing strain, then the iron core efficiency is improved, but the corner portions become larger and the overall iron core size increases
Solution Approach 1:
The patent uses parameter changes by optimizing the radius of curvature to be 3 mm or less, which is a specific quantitative parameter that allows the corner portions to remain compact while the crystal grain size control (2W or less) compensates for the strain, maintaining iron core efficiency. This resolves the contradiction by showing that small radius of curvature does not necessarily lead to poor efficiency when combined with appropriate grain size control.
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
This approach effectively minimizes the deterioration of iron core efficiency by controlling the crystal grain size and curvature, optimizing the magnetic properties and reducing iron loss in the wound core.
Implementation Method 1
The grain-oriented electrical steel sheet has a secondary recrystallization texture in which secondary recrystallization grains are concentrated in the {110} orientation (Goss orientation). The magnetic properties of the grain-oriented electrical steel sheet greatly influence the degree of concentration in the {110} orientation.
Implementation Method 2
portions of steel sheets that become corner portions of a wound core are bent in advance so that a relatively small bent area with a radius of curvature of 3 mm or less is formed and the bent steel sheets are laminated to form a wound core
Data Source
AI summary
This wound core is a wound core including a wound core main body obtained by laminating a plurality of polygonal annular grain-oriented electrical steel sheets in a side view, and the grain-oriented electrical steel sheet has planar portions and bent portions that are alternately continuous in a longitudinal direction, and in at least one bent portion, the crystal grain size Dpx of the grain-oriented electrical steel sheet is 2 W or less.