Conduction Cooled Magnetics Thermal Impedance Reduction
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Solution Overview
Problem
Conventional power processing systems face challenges in reducing the size and mass of magnetic components due to thermal limitations, with inefficient heat transfer coefficients in air cooling and limitations from electrical insulation materials, leading to increased size and cost in high-power systems.
Innovation Solution
A thermally conductive vessel with a cavity conforming to the component's shape, filled with a high thermal conductivity resin, and optimized winding structures such as edge windings and machined windings to minimize thermal impedance and enhance heat transfer, combined with features like external fins and internal cooling for improved heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional air cooling (free convection or forced-air cooling) is used, then the system is simple and cost-effective, but the heat transfer coefficient is limited (0.4 to 3.0 mW/cm2/°C), requiring larger magnetic components
Solution Approach 1:
The patent transitions from air cooling to liquid cooling using transformer oil or other liquid coolants circulated through the magnetic component. The liquid coolant system includes pumps, reservoirs, and cooling channels that enable heat transfer coefficients more than 10 times higher than air cooling, allowing significant reduction in component size while managing thermal loads effectively
Solution Approach 2:
The patent changes the physical state and properties of the cooling medium from gas (air) to liquid (transformer oil or other coolants). This parameter change enables dramatically improved heat transfer coefficients, allowing the magnetic components to be reduced in size by factors of 2 to 10 times while maintaining effective thermal management
2Volume of stationary object
If liquid cooling is used to improve heat transfer coefficient by more than a factor of ten, then magnetic components can be significantly reduced in size, but the inconvenience and economic cost of providing liquid coolant flow offsets this advantage
Solution Approach 1:
The patent combines the cooling function with the existing transformer oil that is already required for electrical insulation in high-voltage applications. By using the same transformer oil for both insulation and cooling purposes, the system eliminates the need for separate cooling systems, reducing complexity while achieving high heat transfer coefficients that enable significant component size reduction
Solution Approach 2:
The transformer oil serves dual functions: electrical insulation for high-voltage windings and thermal cooling for magnetic components. This multi-functional approach eliminates the need for separate cooling infrastructure, making the liquid cooling system practical for high-voltage power processing applications where transformer oil is already mandated
3Device complexity
If coolant contacts only the outer surface of the winding, then the cooling system is simple, but thermal resistance of the winding itself becomes the limiting factor
Solution Approach 1:
The patent segments the cooling approach by applying coolant directly to multiple surfaces of the magnetic component including the core and winding surfaces. The component is divided into multiple thermal zones with dedicated cooling channels contactting different surfaces, enabling heat removal from internal regions rather than relying solely on external convection from the outer winding surface
Solution Approach 2:
The patent introduces a thermally conductive potting compound as an intermediary material between the magnetic component surfaces and the coolant. This compound fills gaps and enhances thermal contact between the component and coolant, reducing thermal resistance at the interface and enabling more efficient heat transfer from the winding and core to the cooling system
4Reliability
If conventional potting compounds are used to encapsulate components, then environmental protection and electrical insulation are provided, but thermal conductivity is insufficient for efficient heat removal
Solution Approach 1:
The patent uses composite potting compounds with enhanced thermal conductivity, combining traditional epoxy or resin materials with thermally conductive fillers such as metal particles, ceramic beads, or other high-conductivity additives. This composite approach maintains the electrical insulation and environmental protection properties while dramatically improving thermal conductivity to enable efficient heat removal from the magnetic component
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
This approach results in reduced size, mass, and cost of power processing systems, enabling the use of high-flux density core materials and efficient heat removal, improving overall system performance and power density.
Implementation Method 1
A thermally conductive encapsulant, such as a resin or potting material fills the gap between the element and the vessel, further improving the cooling ability of the apparatus
Data Source
AI summary
An apparatus for cost-effective and efficient cooling of an active element. The active element may be a magnetic element such as an inductor or a transformer having windings and a core. A thermally conductive vessel has a cavity that is adapted to conform to a surface of the active element, with a small gap remaining between the surface of the active element and the surface of the cavity. The winding is adapted to have a uniform surface, by utilizing an edge winding or a machined winding fabricated from an extruded tube. A thermally conductive encapsulant fills gaps in the apparatus to further improve cooling.