Magnetic Hat Structure for Reducing AC Losses in Power Transformers
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Solution Overview
Problem
In power transformers, especially those used in wireless/contactless power supplies, the increased air gap leads to higher AC resistance and losses due to perpendicular magnetic field lines cutting through copper windings, causing severe proximity effects, which are not effectively addressed by existing technologies.
Innovation Solution
The magnetic structures are designed with a central post having an inverted isosceles trapezoidal, hat, arcuate, or t-shape, increasing the top surface area to shield windings from the magnetic field, making the leakage field parallel to the windings and reducing air gap reluctance, thereby minimizing AC losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the air gap in the transformer increases, then the transformer can be used in wireless/contactless power supplies, but the AC losses increase due to perpendicular magnetic field lines cutting through the windings
Solution Approach 1:
The patent applies local quality by creating a non-uniform magnetic field distribution through the use of magnetic shields and specific winding arrangements. The magnetic shields are positioned to locally redirect field lines, ensuring that in the critical region near the windings, the field lines run parallel rather than perpendicular, thereby reducing AC losses in that specific location while maintaining the overall wireless power transfer function
Solution Approach 2:
The patent introduces magnetic shields as intermediary elements between the magnetic field source and the windings. These shields act as mediators that reshape the magnetic field distribution, causing field lines to follow a path that is parallel to the windings rather than cutting through them perpendicularly, thus reducing eddy current losses without compromising the wireless power transfer capability
2Reliability
If the windings are placed closer to the air gap, then the coupling is improved, but the proximity effects increase the AC resistance
Solution Approach 1:
The patent applies local quality by creating differentiated zones around the windings. Magnetic shields are strategically positioned to provide local field redistribution exactly where the windings are located, ensuring that in this specific region, the magnetic field lines run parallel to the winding surfaces. This localized field control allows the windings to remain close to the air gap for good coupling while preventing proximity effects in the critical vicinity of the windings
3Device complexity
If conventional magnetic structures are used, then the design is simple, but the magnetic field lines are perpendicular to the windings causing high AC losses
Solution Approach 1:
The patent introduces magnetic shields as intermediary elements that modify the magnetic field distribution. These shields are positioned between the magnetic core and the windings to redirect field lines, causing them to run parallel to the winding surfaces rather than perpendicular to them. This intermediary structure effectively reduces AC losses while adding only moderate complexity to the overall design
Solution Approach 2:
The patent addresses the field orientation problem by introducing a spatial dimensionality change. Instead of relying solely on the traditional planar arrangement where field lines naturally cut through windings perpendicularly, the magnetic shields create a three-dimensional field redistribution that redirects lines parallel to the windings, effectively changing the geometric relationship between field lines and winding surfaces
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 configuration significantly reduces AC losses and improves the efficiency of power transformers by ensuring more magnetic field lines are parallel to the windings, decreasing reluctance and enhancing overall system efficiency.
Implementation Method 1
The magnetic structures are designed with a central post having an inverted isosceles trapezoidal, hat, arcuate, or t-shape, increasing the top surface area to shield windings from the magnetic field
Implementation Method 2
decreasing reluctance between the central post and the outer edge
Data Source
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AI summary
Several new and useful features for a magnetic structure are provided. One feature is that the magnetic structures are configured to help minimize the winding's AC losses, improving the system's efficiency. Another feature is that the combination of different magnetic hats creates a shaping path for the magnetic field. Still another feature is that a magnetic hat concept can be applied to a variety of magnetic core shapes.