Transformer Core Leg Segmentation for High Leakage Inductance
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Solution Overview
Problem
Conventional transformers face challenges in achieving high leakage inductance without increasing size or adding additional components, as methods to enhance leakage inductance often result in increased losses or reduced efficiency due to magnetic field interactions and proximity effects.
Innovation Solution
A transformer design with a core that generates distinct magnetic fluxes at different legs, allowing for adjustable leakage inductance without additional components, by varying the cross-sectional area or number of turns of the primary winding legs and incorporating gaps to control magnetic flux, ensuring the flux does not intersect with the secondary winding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the transformer size is reduced, then the compactness is improved, but the leakage inductance becomes insufficient
Solution Approach 1:
The core is divided into multiple legs (first leg, second leg, third leg) with different functions. The first and second legs carry primary windings with different turn ratios, while the third leg provides a magnetic flux path that does not intersect the secondary winding. This segmentation allows independent control of magnetic fluxes to achieve high leakage inductance in a compact structure.
Solution Approach 2:
Different legs of the core are assigned different cross-sectional areas to create local quality differences. The first leg has a larger cross-sectional area than the third leg, allowing the first magnetic flux to be stronger than the second magnetic flux. This local variation in cross-sectional area enables precise control of leakage inductance without increasing overall transformer size.
2Reliability
If a magnet is added between primary and secondary windings to increase leakage inductance, then the leakage inductance is improved, but the loss increases and device complexity increases
Solution Approach 1:
The transformer core structure itself provides the leakage inductance function through its geometric configuration and magnetic flux paths. The difference in cross-sectional areas between legs creates different magnetic flux magnitudes, generating leakage inductance inherently without requiring additional magnetic components. This self-service approach eliminates the need for extra magnets while maintaining energy efficiency.
3Reliability
If the primary winding is wound around the middle leg alone to obtain leakage inductance, then the leakage inductance is improved, but the number of layers increases and efficiency decreases due to proximity effect
Solution Approach 1:
The primary winding is segmented into two separate windings (first primary winding and second primary winding) on different legs. This segmentation distributes the winding layers more evenly, reducing the number of layers on any single leg and minimizing proximity effects. The different turn ratios between the two windings also contribute to generating leakage inductance without excessive layering.
4Reliability
If the separation distance between primary and secondary windings is increased to obtain sufficient leakage inductance, then the leakage inductance is improved, but the transformer size increases
Solution Approach 1:
Instead of uniformly increasing the separation distance between windings, the invention uses local quality differences in the core structure (different cross-sectional areas of legs) to generate leakage inductance. This allows sufficient leakage inductance to be achieved through magnetic circuit design rather than physical spacing, maintaining a compact transformer size.
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 design achieves high leakage inductance without additional losses or efficiency reductions, enabling a sharp frequency characteristic and a wide range of output voltage control by adjusting the switching frequency, suitable for series resonant converters.
Implementation Method 1
a core 10 that forms a magnetic circuit, primary windings 11 that are input sides
Implementation Method 2
a resonant circuit realizes soft switching using the resonance of a resonant inductance Lr and a resonant capacitor Cr
Data Source
Figure 1~2(b)
Figure 3~4
Figure 5(a)~5(c)
AI summary
This transformer (1) is provided with: a core (10) which forms a magnetic circuit and has a middle leg (10a) and a plurality of side legs (10b, 10c) branched from the middle leg (10a); primary windings (11) respectively wound around a first winding leg (10a) and a second winding leg (10b), which are selected from the middle leg (10a) and the side legs (10b, 10c); and a secondary winding (12) wound around either of the first winding leg (10a) or the second winding leg (10b), wherein a first magnetic flux generated by the primary windings (11) from the first winding leg (10a) and a second magnetic flux generated by the primary windings (11) from the second winding leg (10b) differ from each other by a predetermined value or more at a position at which the fluxes do not intersect with the secondary winding (12).