Electromagnetic Coil Assembly with Segmented Core Air Gaps
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Solution Overview
Problem
Existing electromagnetic coils in chokes and transformers face issues such as saturation, nonlinear behavior, cumbersome manufacturing processes, and inefficient cooling due to insulation and eddy currents, particularly in high-frequency applications like switched-mode power supplies.
Innovation Solution
A packaged electromagnetic coil assembly comprising a thermally conductive holder with soft-magnetic elements, a non-insulated coil wound around it, and a thermally conductive, electrically insulating cover, which allows for precise air gap distribution and improved cooling without insulation, using materials that interact weakly with magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air gaps are manufactured in ferromagnetic core elements to prevent saturation, then saturation resistance is improved, but manufacturing precision and ease of manufacture deteriorate due to the need for precise grinding and complex processes
Solution Approach 1:
The magnetic core is divided into multiple separate ferromagnetic core elements (first core element, second core element, third core element) that are positioned around the coil. Air gaps are naturally formed between these segmented elements, eliminating the need for precise grinding of continuous cores. The segmentation allows air gaps to be created through simple positioning rather than complex machining operations.
Solution Approach 2:
A holder structure is introduced as an intermediary component to position and hold the ferromagnetic core elements. The holder provides a framework that maintains precise spacing between core elements, thereby creating consistent air gaps without requiring the core elements themselves to be precisely ground. This intermediary structure simplifies the manufacturing process while ensuring reliable air gap dimensions.
2Reliability
If Litz wire is used to reduce Skin effect and proximity effects, then electrical performance is improved, but ease of operation and manufacturing automation deteriorate due to manual winding requirements
Solution Approach 1:
The invention changes the wire configuration parameter from multi-strand Litz wire to single-strand insulated wire. This parameter change maintains electrical performance through the use of appropriate insulation and winding patterns, while dramatically simplifying the manufacturing process to enable full automation. The single-strand wire can be easily fed through automated winding machines without the complexity of handling multiple insulated strands.
Solution Approach 2:
The invention replaces the manual mechanical winding process required for Litz wire with an automated winding system. By using single-strand insulated wire instead of Litz wire, the mechanical complexity of handling multiple strands is eliminated, allowing standard automated winding machines to be used. This substitution enables industrial automation while maintaining acceptable electrical performance through proper insulation and winding design.
3Reliability
If multiple layers of Litz wire are wound around the ferrite core, then electrical performance is improved, but temperature gradient and heating of the ferrite core worsen
Solution Approach 1:
The invention changes the winding structure parameter from multiple layers of Litz wire to a single-layer or reduced-layer configuration using single-strand insulated wire. This parameter change reduces the radial thickness of the winding, thereby minimizing the temperature gradient between outer and inner layers. The single-strand wire with proper insulation maintains electrical performance while reducing heat accumulation and temperature differential.
4Reliability
If the entire choke is potted into an electrically insulating cover to insulate edgewise-wound coils, then electrical insulation is improved, but cooling efficiency deteriorates due to encapsulation
Solution Approach 1:
The invention extracts the electrical insulation function from the structural cover and assigns it to a dedicated insulation layer. The cover itself is made thermally conductive and is not fully encapsulating, allowing heat to dissipate. The insulation function is taken out and provided by a specific insulation layer positioned between the coil and the cover, separating the electrical insulation requirement from the thermal management requirement.
Solution Approach 2:
The cover is made from composite or composite-like material that combines thermal conductivity with electrical insulation properties. This allows the cover to serve dual functions: providing structural support and heat dissipation pathways while maintaining electrical insulation. The use of materials with these combined properties resolves the contradiction between electrical insulation and cooling efficiency.
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 enables efficient cooling, simplified manufacturing, and reduced nonlinear behavior, making it suitable for high-frequency applications with improved mechanical stability and thermal management.
Implementation Method 1
the holder is made of a first diamagnetic material or a first paramagnetic material... the cover is made of a second diamagnetic material or a second paramagnetic material
Implementation Method 2
the holder is made of a first diamagnetic material or a first paramagnetic material... the cover is made of a second diamagnetic material or a second paramagnetic material
Implementation Method 3
a thermally conductive holder with at least one soft-magnetic element... a thermally conductive and electrically insulating cover which at least partly encloses the coil
Implementation Method 4
A changing, in particular alternating, current flowing through a coil of a choke, for example, creates a changing, in particular alternating, magnetic field
Implementation Method 5
Both ferromagnetic and ferrimagnetic materials typically experience saturation behaviour when magnetic fields above a certain strength are applied to them
Implementation Method 6
at least one soft-magnetic element... the at least one soft-magnetic element is within the convex hull of the holder
Implementation Method 7
electromagnetic coils are wound on ferromagnetic or ferrimagnetic cores providing a magnetic circuit of one or more closed loop paths
Data Source
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AI summary
The invention relates to a packaged electromagnetic coil assembly (1, 1'-1‴‴), comprising (i) a thermally conductive holder (2) with at least one soft-magnetic element (3), wherein the at least one soft-magnetic element (3) is within the convex hull of the holder (2) and held by the holder (2), and wherein the holder (2) is made of a first diamagnetic material or a first paramagnetic material, (ii) a coil (4) formed of non-insulated wire and having a magnetic axis (5) and two ends (6), wherein the non-insulated wire is wound around the holder (2), and (iii) a thermally conductive and electrically insulating cover (7) which at least partly encloses the coil (4), wherein the cover (7) is made of a second diamagnetic material or a second paramagnetic material, wherein the holder (2) and the coil (4) are such that the magnetic axis (5) of the coil (4) passes through at least one air gap provided by the holder (2). The invention also relates to a method for manufacturing a packaged electromagnetic coil assembly (1, 1'-1""").