High Temperature Coil Assemblies Using Ceramic Coated Aluminum Wire
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Solution Overview
Problem
Current high temperature electromagnetic coil assemblies face challenges in maintaining reliability and preventing electrical shorting due to the thin alumina shell of anodized aluminum wire, which abrades during coiling, and existing high temperature wires are either costly or less conductive, making them unsuitable for avionic applications.
Innovation Solution
A high temperature electromagnetic coil assembly is fabricated by applying a high thermal expansion ceramic coating over anodized aluminum wire, which is then coiled around a support structure and cured to form an electrically insulative ceramic body, reducing the likelihood of shorting and increasing breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If anodized aluminum wire with thin alumina shell is used, then cost and conductivity are improved, but the insulative coating abrades during winding causing shorting
Solution Approach 1:
The patent applies a multi-layer composite coating structure on aluminum wire: inner layer of alumina (from anodizing) providing base insulation, middle layer of organic-based material (e.g., polyimide) providing enhanced abrasion resistance, and outer layer of alumina providing heat resistance and additional insulation. This composite structure resolves the contradiction by combining materials with complementary properties to achieve both durability and cost-effectiveness.
Solution Approach 2:
The patent modifies the thickness and composition parameters of the insulative coating by applying multiple layers with varying properties. The inner alumina layer is relatively thin, the middle organic layer provides cushioning and abrasion resistance, and the outer alumina layer restores heat resistance. This parameter optimization allows the coating to withstand winding abrasion while maintaining thermal stability.
2Reliability
If organic-based coatings (e.g., polyimide) are applied to reduce coil-to-coil abrasion, then coating durability is improved, but the coating fails at temperatures exceeding 260°C
Solution Approach 1:
The patent uses a tri-layer composite coating where the middle organic-based material layer (e.g., polyimide) provides abrasion resistance, while the inner and outer alumina layers provide thermal stability. The organic layer is sandwiched between heat-resistant ceramic layers, allowing the system to withstand temperatures above 260°C while maintaining coating integrity through the protective alumina barriers.
Solution Approach 2:
Different layers of the coating serve different local functions: the inner alumina layer provides thermal stability and base insulation, the middle organic layer provides abrasion resistance where mechanical stress occurs during winding, and the outer alumina layer provides heat resistance and environmental protection. This local specialization of material properties resolves the contradiction between abrasion resistance and temperature tolerance.
3Temperature
If ceramic insulated wires are used to operate above 260°C, then temperature tolerance is improved, but cost becomes prohibitively high
Solution Approach 1:
The patent creates a composite coating structure combining inexpensive alumina (from anodizing) with organic-based materials and then firing the assembly to form a ceramic-enriched multi-layer coating. This process uses relatively low-cost aluminum wire and organic coatings, then transforms them into a high-temperature-resistant structure through controlled firing, achieving ceramic-like performance at lower cost than fully ceramic-insulated wires.
Solution Approach 2:
The patent replaces the need for expensive fully ceramic-insulated wires by using a chemical/thermal process (anodizing followed by organic coating application and firing) to create a ceramic-enriched composite structure on inexpensive aluminum wire. This substitution of manufacturing approach achieves high-temperature capability without requiring costly pre-formed ceramic-insulated wire products.
4Reliability
If non-aluminum metal cores (e.g., nickel, copper) are used, then conductivity is improved, but weight and cost increase
Solution Approach 1:
The patent optimizes the aluminum wire parameters by controlling the anodizing process to create a specific alumina shell thickness that provides adequate insulation while maintaining high conductivity of the aluminum core. The multi-layer coating structure further enhances insulation without significantly increasing weight, allowing aluminum to maintain its weight advantage while achieving sufficient electrical performance for high-temperature applications.
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 compact high temperature electromagnetic coil assembly capable of continuous operation above 260°C, minimizing mechanical stress and maintaining structural integrity in avionic applications.
Implementation Method 1
which can be anodized to form an insulative alumina shell over the wire's outer surface
Implementation Method 2
applying a high thermal expansion ceramic coating over an anodized aluminum wire
Implementation Method 3
curing the coated anodized aluminum wire around a support structure and curing the high thermal expansion ceramic coating after coiling
Data Source
AI summary
Embodiments of a high temperature electromagnetic coil assembly are provided, as are embodiments of a method for fabricating such a high temperature electromagnetic coil assembly. In one embodiment, the high temperature electromagnetic coil assembly includes a coiled anodized aluminum wire and an electrically-insulative, high thermal expansion ceramic body in which the coiled anodized aluminum wire is embedded. The electrically-insulative, high thermal expansion ceramic body has a coefficient of thermal expansion greater than 10 parts per million per degree Celsius and less than the coefficient of thermal expansion of the coiled anodized aluminum wire.