Coil Unit Capacitor Electrode Orientation for Eddy Current Suppression
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Solution Overview
Problem
Conventional non-contact power transmission systems for vehicles experience temperature rises due to eddy currents generated on metal surfaces within the coil unit, leading to reduced power transmission efficiency and increased size and weight to mitigate these issues.
Innovation Solution
The coil unit is designed with capacitors having metal electrodes arranged non-perpendicular to the coil's center axis, and capacitors are arranged obliquely along the axis with smaller inclination closer to the center, reducing the magnetic flux perpendicular to the electrodes and thus minimizing eddy currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If capacitors are arranged with electrodes perpendicular to the coil center axis to simplify structure, then device complexity is reduced, but eddy currents are generated on the metal electrode surfaces causing temperature rise and reduced power transmission efficiency
Solution Approach 1:
The patent applies asymmetry by arranging capacitor electrodes at non-perpendicular angles (specifically 45 degrees) relative to the coil center axis, breaking the symmetric perpendicular arrangement that causes eddy currents. This asymmetric orientation prevents magnetic flux from being perpendicular to the electrode surfaces, thereby suppressing eddy current generation while maintaining structural simplicity
Solution Approach 2:
The patent changes the geometric parameter of electrode orientation from perpendicular (90 degrees) to non-perpendicular (45 degrees) relative to the coil center axis. This parameter change fundamentally alters the interaction between magnetic flux and electrode surfaces, eliminating the condition that generates harmful eddy currents while preserving power transmission functionality
2Temperature
If capacitors are moved away from the coil or heat dissipation members are added to reduce temperature rise, then temperature control is improved, but device size and weight increase
Solution Approach 1:
The patent extracts the heat dissipation function from separate components (heat dissipation members) and integrates it into the capacitor arrangement configuration itself. By orienting electrodes at non-perpendicular angles, the structure inherently prevents eddy current generation and thus prevents heat generation at the source, eliminating the need for additional heat dissipation components
Solution Approach 2:
The patent applies preliminary action by designing the capacitor electrode orientation to prevent eddy current generation before heat can be generated. This preventive approach addresses the root cause (eddy currents) rather than treating the symptom (heat), thereby avoiding the need for reactive heat dissipation measures that would increase weight and size
3Loss of energy
If capacitor electrodes are arranged non-perpendicular to the coil center axis to suppress eddy currents, then power transmission efficiency is maintained, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a concrete parameter value (45 degrees) for the non-perpendicular arrangement of capacitor electrodes relative to the coil center axis. This specific angular parameter provides a clear manufacturing target that balances the need to suppress eddy currents with the practical requirements of manufacturing precision, making the design both effective and manufacturable
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 effectively suppresses temperature rises in capacitors, maintaining efficiency while reducing size and weight, and eliminating the need for additional heat dissipation measures.
Implementation Method 1
one of a pair of coils electromagnetically resonate with each other is installed on a ground surface of a supply equipment. The other one is mounted to a vehicle such that power is supplied in a non-contact manner from the coil installed on the ground surface of the power supply equipment to the coil mounted to the vehicle.
Implementation Method 2
the temperature rises due to an eddy current, which is generated on a metal surface, for example, an electrode of a capacitor or the like housed inside the case due to a magnetic field generated from the coil
Data Source
AI summary
A power-supply-side and the power-receiving-side units include power-supply-side and power-receiving-side coils each of which supplies or receives power in a non-contact manner; and a ceramic capacitor provided with an electrode being housed inside power-supply-side and power-receiving-side cases. The ceramic capacitor is arranged such that the electrode is non-perpendicular to each center axis direction of the power-supply-side and power-receiving-side coils.