Epoxy-Encapsulated Coil for Thermal Expansion and Adhesion Stability
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Solution Overview
Problem
Existing coil designs for electrical machines face issues with adhesion of potting compositions due to differing thermal expansion coefficients and high operating temperatures, leading to separation or damage, especially in rotors, and current solutions like additional thermally conductive layers increase production costs.
Innovation Solution
A coil with a winding encapsulated in epoxy resin, where the compressive strength is significantly higher than tensile strength, and the modulus of elasticity is at least 5000 MPa, ensuring high strength and flexibility, with a glass transition temperature of at least 150°C, and a coefficient of linear thermal expansion between copper and steel, reducing stress and maintaining structural integrity at high loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a potting composition is used to encapsulate coils, then strength and stability are improved, but adhesion problems occur due to different coefficients of thermal expansion and high operating temperatures
Solution Approach 1:
The patent modifies the chemical composition parameters of the potting composition by incorporating specific additives and fillers that adjust its thermal expansion coefficient to better match the coil materials. This parameter adjustment allows the potting composition to maintain adhesion under thermal cycling conditions while preserving the strength and stability benefits of encapsulation.
2Reliability
If an additional thermally conductive layer is provided between the cast resin body and supporting body, then adhesion is improved, but production costs increase
Solution Approach 1:
The patent combines multiple functions into the single potting composition material itself. Rather than using separate layers for adhesion, thermal conduction, and mechanical support, the invention integrates these functions into one multi-functional potting composition that adheres directly to both the coil and supporting structures while providing thermal management and mechanical strength.
Solution Approach 2:
The patent employs a composite potting composition containing a matrix material combined with specific fillers and additives that provide both adhesion properties and thermal conductivity simultaneously. This composite approach eliminates the need for separate functional layers while achieving the combined performance of adhesion, thermal management, and mechanical support.
3Strength
If the compressive strength of epoxy resin is significantly higher than tensile strength, then structural integrity at high loads is improved, but flexibility may be reduced
Solution Approach 1:
The patent applies different material properties to different regions or aspects of the coil assembly. The potting composition provides high compressive strength in load-bearing regions while maintaining adequate flexibility in areas requiring thermal expansion accommodation and stress absorption. This localized property distribution allows the system to handle both high mechanical loads and thermal cycling without failure.
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 a cost-effective, reliable, and durable coil that can operate at high rotation rates with adequate safety margins, reducing production costs while ensuring excellent mechanical and thermal performance.
Implementation Method 1
The different coefficients of thermal expansion of the various materials, the high operating temperatures and, in particular in the case of rotors, the high forces acting can by way of example cause separation effects
Implementation Method 2
at a glass transition temperature of the epoxy resin, the modulus of elasticity and the tensile strength assume values which are at least 30% of the values at room temperature
Data Source
AI summary
A coil has a winding that is coated with an epoxy resin in at least some areas, wherein a ratio of a compressive strength of the epoxy resin to the tensile strength thereof at room temperature ranges between 2 and 5, the modulus of elasticity at room temperature is at least 5000 MPa, and at a glass transition temperature of the epoxy resin, the modulus of elasticity and the tensile strength have values amounting to at least 30% of the values at room temperature.