Wireless Power Transfer Foreign Object Detection
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Solution Overview
Problem
Foreign objects, such as metal items, can interfere with the safety, reliability, and efficiency of wireless power transfer systems by affecting the magnetic field and inducing voltage differences, necessitating a detection system to prevent system failure.
Innovation Solution
A wireless power transfer system incorporating a transmitter with a pair of detection coils and a comparison system that generates reference voltages and detects voltage differences to declare the presence of foreign objects, triggering alarms or disabling the transmitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wireless power transfer is implemented using inductive coupling, then power can be transferred without physical contact, but foreign objects in the magnetic field can adversely affect safety, reliability, and efficiency
Solution Approach 1:
The system performs foreign object detection before initiating power transfer by monitoring the magnetic field characteristics. The detection coils measure impedance changes or voltage differences that indicate the presence of foreign objects, allowing the system to prevent unsafe power transfer operations in advance
Solution Approach 2:
The system continuously monitors the magnetic field during power transfer using detection coils and compares the measured values against reference thresholds. When foreign objects are detected through impedance changes or voltage differences, the system provides feedback to disable the transmitter, ensuring ongoing safety
2Reliability
If detection coils are added to detect foreign objects, then system safety is improved, but device complexity increases
Solution Approach 1:
The detection coils are designed to serve multiple functions: they detect foreign objects through impedance changes, verify receiver presence, and monitor power transfer status. The same coil structure used for power transmission also performs detection functions, reducing the need for entirely separate detection hardware
Solution Approach 2:
The patent combines the power transmission coil and detection coil into a single integrated structure where the coil serves both functions. The comparison system is merged with the existing control circuitry of the wireless power transfer system, eliminating the need for completely separate detection hardware
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
Effectively detects foreign objects by comparing induced voltages with reference voltages, ensuring system safety and reliability by preventing power transfer when foreign objects are present, and alerting operators through audible, visual, or mobile alerts.
Implementation Method 1
A wireless power transfer (WPT) system may use the mutual inductance between two inductive coils to provide power to the battery system of the HEV or EV. The electrical grid may provide a voltage to the first coil and, as a result of the inductive coupling between the first coil and the second coil, the second coil will induce a voltage
Implementation Method 2
The first detection coil is configured to generate a first voltage in response to the radiated power from the transmitting coil
Implementation Method 3
The second detection coil is configured to generate a second voltage in response to the radiated power from the transmitting coil
Data Source
AI summary
A wireless power transfer system includes a transmitter with a transmitting coil, a first detection coil, and a second detection coil. The transmitting coil receives and wirelessly radiates power from a power supply to a receiver of a vehicle. In response to the radiated power from the transmitting coil, the first detection coil generates a first voltage, and the second detection coil generates a second voltage. A comparison system is electrically coupled to the transmitter. The comparison system declares presence of a foreign object in proximity to the transmitter in response to a difference between the first voltage and a first reference voltage exceeding a threshold value. The comparison system declares the presence of the foreign object in response to a difference between the second voltage and a second reference voltage exceeding the threshold value. The transmitter is selectively disabled in response to presence of the foreign object being declared.