Modular Coil Array Phase Cancellation for EV Charging EMF Control
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Solution Overview
Problem
Wireless power transfer systems using magnetic induction face challenges in efficiently controlling magnetic flux to minimize leakage and ensure compliance with exposure guidelines, as existing methods either reduce power transfer efficiency or incur high costs and maintenance for active and passive shielding approaches.
Innovation Solution
A modular wireless power transfer coil system with a coil array configuration that includes n×m arrays of coil assemblies, where each coil generates a charging signal out-of-phase with neighboring coils to achieve destructive interference, reducing additive magnetic flux density within a defined exclusion zone for vehicles, and utilizing communication devices to adjust charging parameters based on vehicle-specific data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If magnetic flux control is implemented using traditional shielding methods, then magnetic flux leakage is reduced, but power transfer efficiency decreases and system complexity increases
Solution Approach 1:
The transmitting coil is divided into multiple independently controllable coil segments arranged in an array. Each segment can be individually controlled to generate magnetic flux patterns that cancel each other in specific regions while concentrating flux in the charging zone, thereby reducing magnetic flux leakage without traditional shielding materials that would impede power transfer.
Solution Approach 2:
The system dynamically adjusts the phase and amplitude parameters of each coil segment to create destructive interference patterns in regions where magnetic flux leakage occurs. By changing the phase relationship between adjacent coils (e.g., 180 degrees out of phase), the system reduces magnetic flux density in surrounding areas while maintaining efficient power transfer to the target device.
2Object-affected harmful factors
If active shielding systems are used to control magnetic flux, then exposure guidelines are met, but system complexity and maintenance requirements increase
Solution Approach 1:
The coil array system performs self-control of magnetic flux distribution through automated phase and amplitude adjustment of each coil segment. The system independently manages its own magnetic field patterns without requiring external active shielding components, sensors, or control systems, thereby meeting exposure guidelines while maintaining simple system architecture.
Solution Approach 2:
The same coil segments used for power transfer also serve the dual function of magnetic flux control and exposure mitigation. By programming the phase relationships between coils, the system simultaneously achieves efficient wireless power transfer and compliance with magnetic exposure guidelines, eliminating the need for separate active shielding systems.
3Object-affected harmful factors
If passive shielding materials are deployed, then magnetic flux leakage is minimized, but cost and system complexity increase
Solution Approach 1:
The system replaces passive mechanical shielding materials with an active electromagnetic control approach using the coil array. Instead of using ferromagnetic shields or other passive materials that would physically block and complicate the system, the invention uses controlled electromagnetic fields from the coil segments to cancel magnetic flux leakage through destructive interference, thereby minimizing leakage without adding mechanical shielding complexity.
4Object-affected harmful factors
If coil arrays with out-of-phase charging signals are used, then magnetic flux density in exclusion zone is reduced, but control precision requirements increase
Solution Approach 1:
The system incorporates feedback mechanisms that monitor the actual magnetic flux density distribution and automatically adjust the phase and amplitude of each coil segment to achieve optimal cancellation patterns. This closed-loop control compensates for manufacturing tolerances and ensures precise magnetic flux control without requiring extremely tight manufacturing precision on the coil segments themselves.
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 density within the exclusion zone, enhancing power transfer efficiency while ensuring compliance with exposure guidelines without the need for additional shielding or active control systems, thereby supporting high-power charging for electric vehicles.
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.