Resin Insulated Coil Crack Control via Fabric Segmentation
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Solution Overview
Problem
Resinous insulating materials in electrical coil assemblies are prone to cracking due to thermal cycling and mechanical vibration, leading to potential fatigue cracking of coil wires and device failure, despite existing efforts to prevent crack occurrence.
Innovation Solution
Incorporating a fabric net embedded in the resin base matrix near the outer surface to divide it into segments, along with glass beads dispersed throughout, to increase crack initiation sites and prevent major crack formation, thereby generating multiple tiny cracks instead of larger ones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resinous insulating materials are used to encapsulate coil windings for electrical insulation and mechanical support, then electrical insulation and mechanical support are improved, but crack initiation and propagation occur under thermal cycling and vibration, leading to coil wire failure
Solution Approach 1:
The resin base matrix is segmented into multiple small compartments by embedding a fabric net, creating numerous small cells that distribute stress and prevent crack propagation. This segmentation transforms a single large crack risk into multiple small contained segments, resolving the contradiction between maintaining structural integrity and preventing crack propagation.
Solution Approach 2:
The invention creates a composite structure by combining the resin base matrix with an embedded fabric net reinforcement. This composite material approach enhances the resin's crack resistance while maintaining its electrical insulation properties, addressing both the reliability and strength requirements simultaneously.
2Length of stationary object
If the resin base matrix is made thicker to provide better insulation and mechanical support, then electrical insulation and mechanical support are improved, but the risk of major crack formation increases under thermal stress
Solution Approach 1:
By embedding a fabric net within the thick resin base matrix, the structure is divided into multiple small cells. This segmentation allows the thickness to be maintained for adequate insulation and support while preventing stress concentration that would lead to major cracks in a solid thick structure.
Solution Approach 2:
The fabric net provides localized reinforcement at critical stress points within the resin matrix, creating areas of enhanced crack resistance where needed most, while allowing the rest of the thick resin structure to maintain its insulating and supportive functions.
Data Source
AI summary
An electrically insulated coil assembly for use in a high vibration environment, such as with an aircraft engine, includes a coil of metal wires encompassed by a resin base matrix. A fabric is embedded in the resin matrix near an outer surface of the resin base matrix to divide a thin layer of the resin base matrix into a plurality of segments. In an embodiment, a notch blunting additive is provided in the resin to impede crack propagation.