Stator Insulating Coat Adhesion for Crack Prevention
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Solution Overview
Problem
Existing rotating electric machines face issues with vibration resistance and thermal stress, leading to cracking of insulating coats and potential puncture of electric wires due to high ambient temperatures and operational shocks, as the adhesion strength between resin adhesives and insulating coats is not adequately managed.
Innovation Solution
A stator design with a two-layer insulating coat structure, where the outer coat has a lower adhesion strength to the resin adhesive than the inner coat, preventing cracks from progressing to the electric conductors and ensuring reliable insulation, combined with varnish application to coil end parts for enhanced vibration resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If resin adhesive is applied to fix electric wires in slots, then vibration resistance is improved, but cracks in resin adhesive can propagate to insulating coats causing puncture
Solution Approach 1:
The insulating coat is divided into two layers: an inner coat with high adhesion strength to the resin adhesive, and an outer coat with low adhesion strength. This segmentation allows the inner coat to prevent crack propagation while the outer coat maintains insulation functionality.
Solution Approach 2:
Different portions of the insulating coat are given different adhesion characteristics. The inner coat has high adhesion strength to bond with the resin adhesive and prevent crack propagation, while the outer coat has low adhesion strength to allow controlled delamination and protect the electric conductor.
2Strength
If high adhesion strength between resin adhesive and insulating coat is used, then fixation strength is improved, but thermal stress causes cracks to propagate through the insulating coat
Solution Approach 1:
The two-layer insulating coat structure is designed in advance to cushion against thermal stress. The inner coat provides strong bonding while the outer coat with lower adhesion strength acts as a buffer that can delaminate controllably, preventing stress concentration and crack propagation to the electric conductor.
3Ease of manufacture
If single-layer insulating coat is used, then manufacturing complexity is reduced, but crack propagation leads to puncture risk
Solution Approach 1:
The insulating coat is segmented into two functional layers applied in sequence. The inner coat is applied first for strong adhesion, followed by the outer coat for crack protection. This segmentation enhances reliability while maintaining relatively simple manufacturing processes.
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 design effectively prevents cracks from reaching the electric conductors, thereby preventing puncture of the insulating coats and enhancing the vibration resistance and thermal stability of the stator coil, even under severe temperature and operational stress conditions.
Implementation Method 1
The adhesion strength of the outer coat to the resin adhesive is lower than the adhesion strength of the inner coat to the resin adhesive
Implementation Method 2
the cracking stress will act in such a manner as to break up the adhesion between the resin adhesive and the outer coats, thus preventing the cracks from progressing to the outer coats
Data Source
AI summary
A stator includes an annular stator core, a stator coil and a resin adhesive. The stator coil is comprised of a plurality of electric wires. The electric wires are partially received in slots of the stator core so that the stator coil has a pair of coil end parts protruding outside the slots respectively from opposite axial end faces of the stator core. The resin adhesive is filled in the slots of the stator core and/or applied to the coil end parts of the stator coil. Moreover, each of the electric wires includes an electric conductor and an insulating coat that covers an outer surface of the electric conductor. The insulating coat is two-layer structured to include an inner coat and an outer coat. The adhesion strength of the outer coat to the resin adhesive is lower than the adhesion strength of the inner coat to the resin adhesive.