Insulated Wire Bubble Layer Partial Discharge

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Solution Overview

Problem

Insulated wires for electrical equipment face challenges in achieving high partial discharge inception voltage, heat resistance, and durability due to limitations in insulating film thickness, adhesion, and corona discharge resistance, particularly in high-performance applications like aerospace and automotive systems.

Innovation Solution

Incorporating bubbles into the insulating film of enameled insulated wires by using a mixture of solvents with a high boiling point as a foaming agent, resulting in a thermosetting resin layer with fine bubbles, which enhances partial discharge inception voltage and heat resistance without compromising dielectric breakdown voltage or mechanical strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the insulating film is thickened to improve partial discharge inception voltage, then corona-discharge resistance improves, but the film thickness requirement cannot be met and production complexity increases

Engineering Contradiction:
Improvepartial discharge inception voltageVSAvoidinsulating film thickness
Core Design Contradiction:
ReliabilityVSLength of stationary object

Solution Approach 1:

The patent introduces a porous structure within the insulating film by forming microbubbles during the varnish baking process. This porous structure increases the partial discharge inception voltage by disrupting discharge paths while maintaining a thin overall film thickness, thus resolving the contradiction between improving corona-discharge resistance and meeting thickness requirements.

Inventive Principle:
Principle #31Porous materials

Solution Approach 2:

The patent creates a composite insulating film structure combining a resin matrix with dispersed microbubbles. This composite structure provides both the mechanical integrity of the resin and the electrical performance enhancement from the bubbles, achieving high partial discharge inception voltage without increasing film thickness.

Inventive Principle:
Principle #40Composite materials

2Reliability

If particles are blended into the insulating film to improve corona-discharge resistance, then erosion deterioration reduces, but flexibility lowers and film surface becomes rough

Engineering Contradiction:
Improvecorona-discharge resistanceVSAvoidflexibility and abrasion resistance
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The patent uses a porous microbubble structure instead of solid particles to improve corona-discharge resistance. The gas-filled bubbles provide electrical performance enhancement without the mechanical drawbacks of particle reinforcement, maintaining film flexibility and smooth surface finish.

Inventive Principle:
Principle #31Porous materials

Solution Approach 2:

The patent changes the physical state of the reinforcement phase from solid particles to gas bubbles. This parameter change fundamentally alters the interaction between the reinforcement and the resin matrix, providing electrical performance benefits without compromising mechanical properties like flexibility and surface smoothness.

Inventive Principle:
Principle #35Parameter changes

3Reliability

If the number of baking times is increased to thicken the insulating film, then partial discharge inception voltage improves, but coating film strength decreases due to copper oxide thickening

Engineering Contradiction:
Improvepartial discharge inception voltageVSAvoidadhesion between conductor and insulating film
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The patent forms microbubbles within the insulating film during a single or limited number of baking cycles. This internal porous structure provides the electrical performance enhancement that would otherwise require multiple thickening bakes, thereby avoiding excessive copper oxide formation and preserving adhesion strength.

Inventive Principle:
Principle #31Porous materials

Solution Approach 2:

The patent achieves the desired partial discharge inception voltage through a controlled porous structure formed in a single or limited baking process, rather than applying excessive baking cycles that would lead to copper oxide thickening and adhesion loss. The bubble structure provides sufficient electrical performance with minimal thermal exposure.

Inventive Principle:
Principle #16Partial or excessive action

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 provides insulated wires with improved partial discharge inception voltage, heat resistance, and abrasion resistance, making them suitable for high-performance electrical equipment with enhanced durability and reliability.

Implementation Method 1

Incorporating bubbles into the insulating film of enameled insulated wires by using a mixture of solvents with a high boiling point as a foaming agent, resulting in a thermosetting resin layer with fine bubbles

Methodology Applied
Scientific EffectFoaming: Foam

Implementation Method 2

a layer containing bubbles is formed as an insulating layer by baking a varnish of thermosetting resin

Methodology Applied
Scientific EffectEvaporation: Evaporation

Data Source

PatentEP2824674B1Insulated electric wire having bubble layer therein, electric device, and method for producing insulated electric wire having bubble layer therein
Publication Date: 2018.08.01 FURUKAWA ELECTRIC CO LTD
  • EP2824674B1 patent drawingFigure 1~2
  • EP2824674B1 patent drawingFigure 3~4(c)
  • EP2824674B1 patent drawing

AI summary

An insulated wire, containing: an insulating film made from a thermosetting resin disposed on a conductor directly or via an insulating layer interposed therebetween, in which the insulating film made from a thermosetting resin is a layer containing bubbles prepared by baking a varnish of thermosetting resin, and a layer containing no bubbles is formed as an upper or lower layer of the layer containing bubbles.