Modular Coil Array Phase Cancellation for EV Wireless Charging
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Solution Overview
Problem
Existing wireless power transfer systems using magnetic induction face challenges in efficiently controlling magnetic flux to minimize leakage and ensure safe exposure limits, particularly in high-power applications like electric vehicle charging.
Innovation Solution
A modular coil array system is introduced, comprising an n×m array of coil assemblies arranged in a rectilinear grid pattern. Each coil assembly generates a charging signal out-of-phase with neighboring coils, achieving destructive interference to reduce additive magnetic flux density within a defined exclusion zone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple coil assemblies are operated in-phase to increase power transfer, then power transfer efficiency is improved, but magnetic flux density accumulates and exceeds safety exposure limits
Solution Approach 1:
The patent applies destructive interference to convert the harmful effect of magnetic flux accumulation into a beneficial reduction. By operating coil assemblies out-of-phase, the magnetic flux densities from adjacent coils cancel each other in the far-field region, transforming what would be harmful additive flux into reduced exposure while maintaining power transfer capability
Solution Approach 2:
The patent changes the phase parameter of the charging signals from in-phase to out-of-phase operation. This parameter change fundamentally alters the magnetic flux distribution, causing destructive interference in the far-field region while maintaining efficient power transfer through the near-field coupling
2Object-affected harmful factors
If coil assemblies are operated out-of-phase to reduce magnetic flux leakage, then safety exposure limits are met, but power transfer efficiency may be compromised
Solution Approach 1:
The patent applies different phase relationships to different regions: out-of-phase operation for far-field coils to reduce leakage, and in-phase operation for near-field coils to maintain power transfer efficiency. This localized quality approach allows simultaneous optimization of both safety and performance
3Device complexity
If a single large coil assembly is used to charge the vehicle, then device complexity is reduced, but control over magnetic flux distribution is insufficient
Solution Approach 1:
The patent divides the charging system into multiple discrete coil assemblies arranged in arrays. This segmentation enables independent control of each coil's phase and amplitude, providing precise control over magnetic flux distribution to achieve destructive interference in the far-field while maintaining near-field coupling for power transfer
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 approach effectively reduces magnetic flux leakage, minimizing exposure beyond the exclusion zone while maintaining efficient power transfer, thus ensuring compliance with safety exposure limits and optimizing charging performance.
Implementation Method 1
Wireless Power Transfer (WPT) makes use of magnetic induction in an air core transformer
Implementation Method 2
a charging signal transmitted by a coil assembly destructively interferes with a charging signal transmitted by the neighboring coil assembly to reduce additive magnetic flux density
Data Source
AI summary
Modular coil assemblies for wireless charging of vehicles have coil geometries and communications designed to limit electromagnetic field (EMF) levels in regions where humans or other living objects may be present. The modular coil assemblies are designed with the ability to shape the magnetic field to be predominately within shielding provided by the auto chassis by, for example, providing side-by-side phase cancellation or diagonal versus front-to-back (for 1×3, 2×3 array configurations) phase cancellation. The power levels and frequency offset pairwise compensation of the respective coils may be controlled to improve cancellation and thus to reduce magnetic field exposure potential. The phase cancellation of the magnetic flux density from respective coil assemblies varies over a range to provide, for example, ˜50% cancellation at 125° offset and up to ˜100% cancellation at 180°. Charging profiles for vehicles and charging stations may be used to maximize the magnetic flux density cancellation during charging.