Rectangular Insulated Wire Multilayer Structure Bending Workability
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Solution Overview
Problem
Insulated wires with rectangular cross-sections face challenges in achieving a high space factor due to brittleness and cracking issues during bending, particularly at small curvature radii, which affects their thermal aging resistance and edge-wise bending workability.
Innovation Solution
A multilayer insulated wire structure comprising a thermosetting resin layer, a thermoplastic resin layer, and an optional interlayer, where the thermoplastic resin layer is thinner than the thermosetting resin layer, enhancing edge-wise bending workability and thermal aging resistance while maintaining a high space factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the curvature radius of the corner portion of a rectangular conductor is made small to increase the space factor, then the space factor is improved, but the insulating coat layer becomes brittle and cracks during bending processing
Solution Approach 1:
The patent applies composite materials by combining thermosetting resin and thermoplastic resin in a multilayer insulating structure. The thermosetting resin layer (inner layer) provides excellent thermal aging resistance and adhesion to the conductor, while the thermoplastic resin layer (outer layer) provides flexibility and crack resistance during bending. This composite structure allows the use of small curvature radius conductors (high space factor) without causing cracks in the insulating layer.
2Reliability
If the insulating film is thickened to improve thermal aging resistance and prevent partial discharge, then thermal aging resistance is improved, but the space factor decreases
Solution Approach 1:
The patent applies local quality by creating different thicknesses of insulating layers at different locations. The thermosetting resin layer is thicker at the corner portions (where thermal aging and partial discharge risks are highest) and thinner at the flat portions. This localized thickness distribution provides enhanced thermal aging resistance and electrical insulation where needed while maintaining a compact overall structure for high space factor.
Solution Approach 2:
The multilayer composite structure allows optimization of each layer's function: the thermosetting resin layer (inner) provides thermal stability and adhesion with controlled thickness, while the thermoplastic resin layer (outer) provides mechanical protection and flexibility. This enables achieving adequate thermal aging resistance without excessive overall thickness that would reduce space factor.
3Area of moving object
If a rectangular wire is used to increase the space factor, then the space factor is dramatically improved, but the corner portion becomes extremely brittle to bending processing
Solution Approach 1:
The patent uses composite materials with the outer thermoplastic resin layer providing flexibility and crack resistance during bending operations, while the inner thermosetting resin layer maintains the rectangular shape and provides thermal stability. This composite structure enables excellent bending workability even with small curvature radius rectangular conductors, resolving the contradiction between space factor improvement and manufacturing ease.
Data Source
Figure 1(a)~2
Figure 3~4
AI summary
An insulated wire containing: at least one thermosetting resin layer; and at least one thermoplastic resin layer, provided in this order on a conductor having a rectangular cross-section, a curvature radius r of corner portions at both edges of at least one short side of the conductor being 0.6 mm or less, in which thickness t1 of the corner portion of the thermosetting resin layer and thickness t2 of the corner portion of the thermoplastic resin layer satisfy a relation expressed by the following Formula 1: t2/t1<1; and a method of producing thereof, a motor coil, and an electric/electronic equipment.