Vacuum Switchgear Composite Overwrap Insulation

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Solution Overview

Problem

Vacuum switch or interrupter devices in high voltage switchgear face issues with thermal and mechanical stress, leading to premature failure due to differential expansion rates of materials, misalignment, and electrical stress, which affects reliability and operational efficiency.

Innovation Solution

A mounting structure and insulation system using a composite overwrap layer with similar thermal expansion coefficients to the ceramic insulator, eliminating the need for separate buffer materials and simplifying manufacturing, while providing robust mechanical and electrical isolation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a rigid casting encapsulates the vacuum bottle, then mechanical strength and positioning are improved, but thermal stress and material incompatibility cause breakage and premature failure

Engineering Contradiction:

Improvemechanical strengthVSAvoiddevice reliability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent introduces an elastomeric buffer material as an intermediary layer between the rigid casting and the vacuum bottle. This buffer material absorbs thermal expansion differences and mechanical stresses, preventing direct stress transmission to the brittle vacuum bottle while maintaining the structural support function of the casting.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs a composite structure combining rigid casting material (epoxy or rigid polymer) with elastomeric buffer material. This composite approach allows each material to perform its optimal function: the rigid casting provides overall structural strength and positioning, while the elastomeric buffer provides thermal and mechanical stress relief.

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If elastomeric buffer material is added to reduce thermal stress, then thermal compatibility is improved, but device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improvethermal compatibilityVSAvoidmanufacturing ease

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

The elastomeric buffer material is pre-formed as a separate component before assembly into the final device. This preliminary preparation allows for optimized manufacturing of each component independently, with the buffer material being molded to precise dimensions and then integrated into the casting-bottle assembly, simplifying the overall manufacturing process.

Inventive Principle:

Principle #10Preliminary action

3Ease of operation

If misalignment occurs between operating shaft and bottle axis, then ease of assembly is improved, but mechanical stress and binding increase causing operational failure

Engineering Contradiction:

Improveease of assemblyVSAvoidoperational reliability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The elastomeric buffer material serves as a pre-positioned cushioning element that compensates for potential misalignment between the operating shaft and bottle axis. This buffer absorbs minor alignment errors and prevents binding during operation, ensuring reliable contact movement without requiring extremely precise alignment during assembly.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

4Adaptability or versatility

If thermal cycling occurs during operation, then operational flexibility is improved, but cumulative thermal stress causes fatigue and premature failure

Engineering Contradiction:

Improveoperational flexibilityVSAvoidservice life

Core Design Contradiction:

Adaptability or versatilityVSDuration of action of stationary object

Solution Approach 1:

The patent explicitly accounts for thermal expansion by selecting an elastomeric buffer material with appropriate thermal expansion characteristics that match or complement the vacuum bottle and casting materials. This allows the buffer to expand and contract harmoniously with the surrounding components during thermal cycling, preventing stress concentration and fatigue failure.

Inventive Principle:

Principle #37Thermal expansion

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 enhances the structural integrity and reliability of vacuum switchgear by reducing thermal stress, improving alignment, and preventing electrical discharges, thus extending the device's lifespan and operational efficiency.

Implementation Method 1

The materials used to fabricate the casting and the bottle may have different thermal coefficients of expansion, and heat generated by making (closing the contacts), breaking the circuit (opening the contacts), and interrupting fault currents can be significant, which causes the materials to expand rapidly at different rates.

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

a vacuum switch or interrupter having a movable contact that engages or disengages a fixed contact within a vacuum chamber

Methodology Applied

Scientific EffectVacuum: Vacuum

Data Source

PatentUS7488916B2Vacuum switchgear assembly, system and method

Publication Date: 2009.02.10 EATON INTELLIGENT POWER LTD

AI summary

Insulated vacuum switchgear and active switchgear elements therefor are provided with a rigid support structure mechanically isolating a vacuum insulator from axial loads in use without reinforcing or insulating encapsulations. At least one of the elastomeric insulating housing and the support structure directly contacts an outer surface of the insulator. Systems and methods for assembling the switchgear are also provided.