Thermally Conductive Foam for Electrical Machines
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Solution Overview
Problem
Conventional rigid foam systems used for thermal insulation and mechanical stabilization of electrical components face challenges such as cracking due to thermal expansion mismatch, limited spatial thermal connection, and complex processing, which restricts the size of thermal bridges and electrical insulation capabilities.
Innovation Solution
A rigid foam system with metallic particles added homogeneously, which expands significantly upon curing to create a solid state with enhanced thermal conductivity while remaining electrically insulating by maintaining the metallic particle concentration below the percolation threshold, allowing for larger thermal connections without electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid uncrosslinked thermosets are used for thermal bonding, then thermal conductivity can be improved, but the size of thermal bridges is limited to a few millimeters due to rheological properties
Solution Approach 1:
The patent changes the physical state parameter from liquid uncrosslinked thermoset to expandable foam (which expands to solid). This parameter change allows the material to flow into larger spaces in expandable state, then固化 to maintain structural integrity and thermal conduction paths over distances of several centimeters, resolving the limitation of thermal bridge size
Solution Approach 2:
The patent utilizes phase transition from liquid/expandable state to solid state. The foam expands during curing to fill the space between components, creating continuous thermal conduction paths. This phase transition enables thermal bonding over larger distances by allowing the material to adapt to the geometry and then solidify to maintain thermal contact
2Temperature
If metallic particles are added to increase thermal conductivity, then thermal conductivity is improved, but electrical conductivity increases above the percolation threshold
Solution Approach 1:
The patent carefully controls the concentration parameter of metallic particles to remain below the percolation threshold. This parameter control allows the material to maintain electrical insulation properties while still achieving enhanced thermal conductivity through the sub-threshold metallic particle network
Solution Approach 2:
The patent creates a composite material system combining expandable foam with metallic particles at controlled concentrations. This composite structure achieves thermal conductivity enhancement through the metallic particles while the foam matrix and sub-threshold particle concentration maintain electrical insulation properties
3Reliability
If conventional rigid foam systems are used, then electrical insulation is maintained, but thermal conductivity is insufficient for effective heat dissipation
Solution Approach 1:
The patent creates a composite material combining expandable foam with metallic particles. The foam matrix provides electrical insulation while the metallic particles dispersed within enhance thermal conductivity, achieving both requirements simultaneously through the composite structure
4Temperature
If liquid uncrosslinked thermosets are used for potting, then thermal bonding is possible, but the process is complex involving preheating, material preparation, dosing, and curing
Solution Approach 1:
The patent uses a single-component expandable foam that can be directly applied and then cures in place. This eliminates the need for complex multi-step processes involving preheating, material preparation, and dosing of multiple components. The material is applied in its expandable state and transforms to solid, providing thermal bonding without the complexity of conventional thermoset processing
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 system achieves higher thermal conductivity and mechanical stability with electrical insulation, enabling effective heat dissipation over larger distances and improved component integration in electrical machines.
Implementation Method 1
The volume of the rigid foam system in the second state is at least 5% greater than in the first state
Implementation Method 2
the homogeneous addition of metallic particles to the rigid foam system to increase its thermal conductivity
Data Source
AI summary
The invention relates to a rigid foam system (20) comprising a rigid foam (24) and being convertible from a first state into a second state. The first state is a liquid state and the second state is a solid state. The volume of the rigid foam system (20) in the second state is at least 5% larger than the volume in the first state. It is often desired, in electrical machines, that different components should be thermally interconnected while said components are maintained electrically isolated. For this reason, the rigid foam system (20) is characterised in that, in order to increase the thermal conductivity, metal particles (22) are homogeneously mixed into the system as an admixture, and at the same time, the concentration of the admixed metal particles (22) lies below the percolation threshold.