Current-Dependent Inductor Flux Bifurcation for Lower Fringing Loss
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Solution Overview
Problem
Existing passive, current-dependent inductivities face challenges in minimizing losses while maintaining a compact size, as they suffer from increased magnetic field fringing and saturation issues that lead to inefficiencies and higher losses at higher currents.
Innovation Solution
A passive, current-dependent inductivity design featuring a magnetic core with a saturation region between the bank air gap and windings, where the magnetic flux bifurcates into paths with varying resistances, optimizing magnetic flux guidance and reducing losses by using materials with specific permeability characteristics and strategically placing air gaps to manage saturation effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a stepped air gap is used in the central leg to achieve current-dependent inductivity, then the inductivity value decreases with increasing current, but the magnetic field fringing causes high losses and requires increased distance between windings and central leg
Solution Approach 1:
The common bar is divided into a first section and a second section with different cross-sectional areas, creating distinct magnetic path segments. The first section has larger cross-section for low-current operation, while the second section with smaller cross-section activates at higher currents, providing segmented saturation behavior that reduces fringing losses
Solution Approach 2:
Different sections of the magnetic core are given different cross-sectional areas to create localized saturation characteristics. The first section maintains larger dimensions to guide flux away from windings, while the second section's smaller dimensions create controlled saturation that reduces fringing field interaction with windings at high currents
2Volume of moving object
If the first region acts as air gap at low currents to maintain compact size, then the inductivity is determined by this small region, but at saturation the combined air gap size increases fringing field reach and causes high losses
Solution Approach 1:
The air gap region is segmented into first and second sections with different cross-sectional areas. The first section provides the primary air gap effect for compact low-current operation, while the second section's smaller cross-section creates a bottleneck that limits fringing field expansion at high currents, reducing losses
Solution Approach 2:
The solution transitions from a single-dimensional air gap approach to a two-dimensional segmented structure with varying cross-sections. This dimensional complexity allows the first section to provide compactness while the second section's reduced dimensions constrain fringing fields, solving both size and loss issues
3Adaptability or versatility
If multiple air gaps of different sizes are used in parallel legs to achieve current-dependent inductivity, then the inductivity drops as current increases and legs saturate, but all air gaps are in immediate vicinity of windings causing fringing field interactions and losses
Solution Approach 1:
The harmful fringing field interaction is eliminated by extracting the air gap from the immediate vicinity of the windings. The air gap is placed in the common bar away from the winding window, so fringing fields do not interact with windings even when the air gap is effectively active at high currents
4Adaptability or versatility
If active current-dependent inductivity with control circuit is used to adapt inductivity, then great flexibility is achieved, but additional circuitry increases complexity, failure risk and costs
Solution Approach 1:
The inductivity adapts to current conditions automatically through the passive saturation characteristics of the segmented magnetic core. The first and second sections naturally transition between active states based on current magnitude, providing self-regulating current-dependent inductivity without external control circuits or active components
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 minimizes losses and maintains a compact size by effectively guiding the magnetic flux, reducing fringing field interactions with windings, and allowing for efficient operation across a range of currents, with clear transitions in inductance values facilitating circuit design and fault detection.
Implementation Method 1
The saturation region (5) is arranged such that a magnetic flux path bifurcates into a first path passing through the saturation region and into a second path passing through the bank air gap (4) and bypassing the saturation region (5). The magnetic resistance of the first path is lower than the magnetic resistance of the second path for winding currents below a first saturation current and whereby the magnetic resistance of the second path is lower than the magnetic resistance of the first path for winding currents above the first saturation current due to significant saturation effects occurring in the saturation region (5).
Data Source
AI summary
A passive, current dependent inductivity (1) comprises a magnetic core (2), windings (3) and at least one bank air gap (4). A saturation region (5) made of magnetic material is arranged between the bank air gap (4) and the windings (3). A magnetic flux path (6) bifurcates into a first path (61) passing through the saturation region (5) and into a second path (62) passing through the bank air gap (4) and bypassing the saturation region (5). The magnetic resistance of the first path (61) is lower than the magnetic resistance of the second path (62) for winding currents below a first saturation current (7a) and whereby the magnetic resistance of the second path (62) is lower than the magnetic resistance of the first path (61) for winding currents above the first saturation current (7a) due to saturation of the saturation region.