Inductive Energy Transfer Foreign Body Detection
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Solution Overview
Problem
Existing inductive energy transmission systems for electric vehicles face safety hazards due to metallic foreign bodies inducing eddy currents, which can lead to heating and potential damage or injury, especially in publicly accessible areas with automated operations, where previous safety measures are insufficient.
Innovation Solution
A device with a regular two-dimensional arrangement of measuring inductances adjacent to the primary inductance, connected to impedance measuring and evaluation devices, detects the presence, size, and position of metallic objects by measuring impedance changes, allowing for the deactivation of energy transfer and warning signals to prevent hazards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If inductive energy transmission is used to charge electric vehicles, then contactless energy transfer is achieved, but metallic foreign bodies in the field area can be heated by eddy currents causing damage or injury
Solution Approach 1:
The system performs foreign body detection before initiating full power inductive energy transmission. The control unit checks the detection signal from the measuring inductance to determine if a metallic foreign body is present in the intermediate space, and only allows energy transmission when the area is clear, thus preventing harmful heating before it can occur.
Solution Approach 2:
A measuring inductance is introduced as an intermediary component between the primary inductance and the secondary inductance. This measuring inductance detects the presence of metallic foreign bodies through changes in its electrical impedance caused by eddy currents, providing early warning without requiring full power transmission.
2Reliability
If previous safety measures like brushes or manual inspection are used, then some foreign body detection is achieved, but these measures are insufficient for automated operation and high security requirements
Solution Approach 1:
The patent replaces mechanical detection methods (brushes, manual inspection) with an electromagnetic detection system. The measuring inductance uses electrical impedance changes to detect metallic foreign bodies automatically, enabling the system to meet high security requirements for automated operation without human intervention.
3Adaptability or versatility
If a large number of primary coils are used to eliminate precise alignment requirements, then alignment tolerance is improved, but the complexity of detecting foreign bodies increases
Solution Approach 1:
The detection system is segmented by using a separate measuring inductance distinct from the primary inductance used for energy transmission. This segmentation allows the detection function to operate independently with its own simple circuitry, avoiding the complexity that would arise from trying to integrate detection into a large array of primary coils.
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 solution enhances operational reliability by accurately detecting conductive foreign bodies, preventing overheating and ensuring safe operation, even in automated systems, by distinguishing between metallic objects and vehicles during inductive energy transfer.
Implementation Method 1
If objects made of metallic materials are brought into the area of such a field, eddy currents are induced in them, which lead to heating
Implementation Method 2
a magnetic field of high field strength and flux density is built up between a stationary primary coil and a vehicle-side secondary coil. This is necessary in order to induce a sufficiently high current in the secondary coil
Implementation Method 3
a magnetic field of high field strength and flux density is built up between a stationary primary coil and a vehicle-side secondary coil
Data Source
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AI summary
The invention relates to a device for the inductive transfer of electric energy from a stationary unit comprising at least one primary inductance to a vehicle that is adjacent to said unit and has at least one second inductance. The stationary unit has a device for detecting the presence of an electrically conductive object in a predetermined area that borders the primary inductance. In particular, said area can be the area lying between the primary inductance and the second inductance during the inductive energy transfer. The device has at least one measuring inductance, a measuring unit for measuring the impedance of the measuring inductance and an evaluation unit that is connected to the measuring unit. The measuring inductance can be identical to the primary inductance. Preferably, the device is equipped with a plurality of measuring inductances which form a regular two-dimensional arrangement extending approximately on one plane, said plane lying perpendicular to the main direction of the magnetic field that is generated by the primary inductance during operation.