Inductive Power Transfer Coupling Structures with Ferrite Gaps and Multifilar Windings
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Solution Overview
Problem
High-power inductive power transfer systems face challenges in managing core losses and overheating at higher frequencies, particularly when charging electric vehicles, due to the need for thicker wires or multiple filars, which can lead to unequal current distribution and efficiency losses.
Innovation Solution
A magnetic structure with a plurality of ferrite pieces separated by gaps to control relative permeability and prevent partial saturation, combined with a multifilar winding design where each filar crosses others equally, ensuring balanced inductance and current distribution, and the use of heat transfer means like heat pipes to manage thermal issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If thicker wires or multiple filars are used to handle high power, then power transfer capability is improved, but current distribution becomes unequal and efficiency is reduced
Solution Approach 1:
The winding is divided into multiple filars (individual wire strands) that are arranged in a specific geometric pattern. Each filar carries a portion of the total current, and the segmentation allows for more uniform current distribution compared to using a single thick wire, thereby reducing resistive losses while maintaining high power transfer capability.
Solution Approach 2:
The patent applies different spatial arrangements to different filars based on their local position within the winding structure. Filars positioned closer to the magnetic core have different inductance characteristics than those farther away, and the design compensates for these local variations to achieve overall current balance across all filars.
2Productivity
If higher frequencies are used for power transfer, then charging speed is improved, but core losses increase and overheating occurs
Solution Approach 1:
The patent optimizes the geometric parameters of the multifilar winding configuration (such as filar spacing, arrangement pattern, and proximity to the core) to minimize eddy current losses and hysteresis losses in the magnetic core at high operating frequencies. This allows higher frequencies to be used for faster charging while controlling core losses through careful structural design.
3Ease of operation
If base winding is made physically thin, then installation flexibility and gap tolerance are improved, but inductance control becomes more difficult
Solution Approach 1:
The patent uses localized magnetic shunts or flux concentrators positioned at specific points within the thin winding structure to enhance the magnetic path and increase effective inductance without increasing the overall physical thickness. This allows the winding to remain thin and flexible for installation while achieving the required inductance values through strategic local magnetic field enhancement.
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 reduces core losses, mitigates overheating, and maintains efficient power transfer while allowing for flexible installation and reduced risk of damage, even under high power conditions.
Implementation Method 1
A magnetic structure with a plurality of ferrite pieces separated by gaps to control relative permeability and prevent partial saturation
Implementation Method 2
the separation distance is selected to prevent partial saturation of a selected region of the structure
Implementation Method 3
a multifilar winding design where each filar crosses others equally, ensuring balanced inductance and current distribution
Implementation Method 4
the use of heat transfer means like heat pipes to manage thermal issues
Implementation Method 5
heat transfer means such as heat pipes to manage thermal issues
Data Source
AI summary
A magnetic structure for wireless power transfer has a plurality of pieces of magnetically permeable material arranged along a first dimension. Each piece is separated from a neighbouring piece by a gap defining a separation distance which is selected to prevent partial saturation of a region of the structure.