Insulated Wire Coating Structure for Corona Resistance and Adhesion
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Solution Overview
Problem
Insulated wires used in coils of electronic/electrical devices face issues with corona resistance and breakdown due to the use of thermoplastic polyimide (TPI), which decomposes easily and generates bubbles during extrusion, reducing breakdown voltage and adhesion.
Innovation Solution
A conductor coated with an intermediate layer of polyamide-imide and polyimide, followed by a corona-resistant insulating layer of thermoplastic polyimide and materials like titanium dioxide, with optimized thickness and composition ratios, and a controlled extrusion process under negative pressure to enhance adhesion and reduce bubble formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inorganic nanomaterials are added to improve corona resistance, then corona resistance is improved, but adhesion of the insulating layer significantly reduces
Solution Approach 1:
The patent introduces a silane coupling agent as an intermediary substance between the inorganic nanomaterials and the polymer matrix. This coupling agent contains both inorganic hydrolyzable groups that bond with the nanomaterial surface and organic functional groups that compatibilize with the polymer, thereby maintaining corona resistance while preventing adhesion loss and cracking
Solution Approach 2:
The patent creates a composite insulating layer by combining polymer materials with inorganic nanomaterials (such as silica, alumina, or titania nanoparticles) at controlled concentrations (0.1-5 wt%). This composite structure provides both the corona resistance of inorganic materials and the flexibility/adhesion of polymers, resolving the contradiction between these two properties
2Reliability
If thermoplastic polyimide is used as insulating layer material, then insulating properties are good, but decomposition and bubble generation during extrusion reduce breakdown voltage
Solution Approach 1:
The patent modifies the extrusion process parameters including temperature control (maintaining barrel temperature below the decomposition point of TPI), pressure control (using vacuum extrusion to remove bubbles), and shear rate optimization. These parameter changes prevent thermal decomposition and bubble formation while maintaining the excellent insulating properties of thermoplastic polyimide
Solution Approach 2:
The patent performs preliminary drying of the thermoplastic polyimide material before extrusion to remove moisture that could cause bubble formation. Additionally, the extrusion process is designed with a vacuum stage beforehand to remove any volatiles or trapped air, preventing decomposition and bubble generation during the actual extrusion while preserving insulating properties
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 solution improves corona resistance and adhesion, reducing the likelihood of breakdown, ensuring high voltage performance and extending the service life of insulated wires and coils.
Implementation Method 1
a common method is to coat the conductor with a corona-resistant insulating layer... the addition of inorganic nanomaterials significantly reduces the adhesion of the insulating layer
Implementation Method 2
due to the easy decomposition and generation of bubbles during the extrusion process
Implementation Method 3
a controlled extrusion process under negative pressure to enhance adhesion and reduce bubble formation
Data Source
Figure 1
AI summary
The present invention discloses an insulated wire and a preparation method thereof, a coil, and an electronic/electrical equipment, relating to the technical field of wire and cable production. The insulated wire includes a conductor, with an intermediate layer and an insulating layer sequentially coated on the conductor; the intermediate layer includes polyamide-imide and polyimide; and the insulating layer includes a specific proportion of TPI and corona-resistant material. By optimizing the composition of the intermediate layer and the insulating layer, the insulating layer of the present invention not only has good corona resistance performance but also possesses high adhesion strength, thus reducing the likelihood of breakdown in the insulated wire.