Capacitor-Compensated Litz Wire for Uniform Inductive Charging

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Solution Overview

Problem

The use of Litz wire in inductive charging systems for electric vehicles leads to heterogeneous current distribution and additional losses due to induced impedance, reducing energy efficiency and causing premature wear.

Innovation Solution

A Litz wire design with stranded or braided electrical conductors, combined with capacitors in series to compensate for impedance differences, ensuring homogeneous current distribution and reducing losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If Litz wire is used to reduce skin effect losses, then charging efficiency is improved, but heterogeneous current distribution causes premature wear

Engineering Contradiction:
Improvecharging efficiencyVSAvoidwire durability
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The patent modifies the electrical parameters by adding series capacitance to each conductor, which equalizes the impedance and ensures uniform current distribution, preventing localized overheating and premature wear while maintaining high charging efficiency

Inventive Principle:
Principle #35Parameter changes

2Loss of energy

If capacitors are added in series with each conductor, then current distribution is homogenized, but device complexity increases

Engineering Contradiction:
Improvecurrent distribution uniformityVSAvoidnumber of components
Core Design Contradiction:
Loss of energyVSDevice complexity

Solution Approach 1:

The patent applies homogeneity by using identical capacitor values for each conductor in the Litz wire, creating uniform impedance characteristics across all conductors. This standardized approach simplifies the design process and component selection while achieving the goal of homogeneous current distribution

Inventive Principle:
Principle #33Homogeneity

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 achieves improved energy efficiency and reduced wear by balancing current distribution across the conductors, minimizing impedance differences and associated losses.

Implementation Method 1

capacitors respectively arranged in series with the conductors, the capacitors being configured to compensate for differences between the respective impedances of the electrical conductors

Methodology Applied
Scientific EffectCapacitance: Capacitance

Implementation Method 2

The Litz wire has the advantage of reducing losses due to a phenomenon known as the 'skin effect.'

Methodology Applied
Scientific EffectSkin effect: Skin Effect

Implementation Method 3

Coils are used to transfer energy via a magnetic field

Methodology Applied
Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentEP4445393B1Device and system for transferring electrical energy
Publication Date: 2025.12.24 ELECTRICITE DE FRANCE
  • EP4445393B1 patent drawingFigure 1
  • EP4445393B1 patent drawingFigure 2
  • EP4445393B1 patent drawingFigure 3(a)~3(b)

AI summary

The invention relates to a device (2) for transferring electrical energy, comprising: a Litz wire (20) comprising electrical conductors (22) stranded or braided together, the Litz wire (20) being wound about itself to form a winding (6) capable of forming a magnetic coupler (3) with another winding (8); capacitors (C T1 , C T2 , C T3 ) respectively arranged in series with the conductors (22), the capacitors (CT T1 , C T2 , C T3 ) being configured to compensate for differences between the respective impedances of the electrical conductors (22).