Semiconductive Insulating Layer for Rotating Electrical Machine Winding

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Solution Overview

Problem

In rotating electrical machines, thermal stress between the winding and core due to different coefficients of thermal expansion causes peeling or cracking in the insulating layers, leading to corona discharges and unstable support against electromagnetic forces, which results in vibration and noise.

Innovation Solution

A semiconductive insulating layer is formed using a center-folded continuous semiconductive sheet wrapped between the inter-layer and protective insulation, with a thermal stress relaxation layer to maintain electric continuity and mechanical stability, preventing corona discharges and ensuring stable support against electromagnetic forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a semiconductive insulating layer with a separated layer between two components is used, then corona discharge is suppressed at peeled parts, but the insulating layer becomes discontinuous and corona discharge cannot be completely suppressed

Engineering Contradiction:

Improvecorona discharge suppressionVSAvoidcontinuity of semiconductive insulating layer

Core Design Contradiction:

Object-affected harmful factorsVSStability of the object's composition

Solution Approach 1:

The semiconductive insulating layer is divided into two components: a groundwall insulating layer and a protective insulation layer, with a separating layer between them. This segmentation allows each layer to perform its specific function while maintaining overall effectiveness in preventing corona discharge.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A separating layer is introduced as an intermediary between the groundwall insulating layer and the protective insulation layer. This separating layer resolves the contradiction by allowing controlled discontinuity while maintaining electrical potential equilibrium through the semiconductive properties of the outer layer, preventing corona discharge even at discontinuous points.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If the semiconductive insulating layer is made discontinuous to allow thermal stress relaxation, then peeling and cracking are reduced, but unstable support against electromagnetic forces occurs causing vibration and noise

Engineering Contradiction:

Improveresistance to peeling and crackingVSAvoidstability against electromagnetic forces

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

Different regions of the insulating structure are assigned different properties: the groundwall insulating layer provides mechanical strength and continuity for electromagnetic force support, while the protective insulation layer with separating layer provides thermal stress relaxation and corona discharge prevention at critical interfaces.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The insulating structure uses a composite of multiple materials with different properties: the groundwall insulating layer uses materials with high mechanical strength, the protective insulation layer uses semiconductive materials for electrical stability, and the separating layer uses materials that accommodate thermal expansion differences. This composite structure resolves the contradiction between mechanical stability and thermal stress resistance.

Inventive Principle:

Principle #40Composite materials

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 effectively suppresses corona discharges and provides stable support against electromagnetic forces, preventing peeling and cracking, and maintaining insulation integrity by maintaining electric continuity and absorbing thermal stress.

Implementation Method 1

a thermal stress relaxation layer is formed inside the center-folded semiconductive sheet, the thermal stress relaxation layer relaxation thermal stress exerted in the thickness direction of the insulating layers

Methodology Applied

Scientific EffectThermal stress relaxation: Stress Relaxation

Implementation Method 2

even if peeling or a crack occurs in the separated layer, the interior of the semiconductive insulating layer is kept at approximately the same potential, so a corona discharge, which would otherwise rapidly deteriorate the insulation resin, does not occur at the peeled part or crack

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS7804218B2Rotating electrical machine winding, rotating electrical machine, and semiconductive insulating component used therein

Publication Date: 2010.09.28 MITSUBISHI GENERATOR CO LTD

AI summary

When a rotating electrical machine winding is inserted into a slot with a protective insulation intervening between them, a semiconductive insulating layer is lap-wound between an interlayer insulating layer of the rotating electrical machine winding and the protective insulation, the semiconductive insulating layer being formed by center-folding a continuous semiconductive sheet in the longitudinal direction. A thermal stress relaxation layer is provided inside the center-folded continuous semiconductive sheet so that thermal stress exerted in thickness direction of the insulating layers is absorbed.