Abstract
Recently, wireless charging technologies for large moving objects, such as electric vehicles and robots, have been actively researched. The power transmitting and receiving coils in most large moving objects are structurally separated by a given distance, which exposes a high output power to the outside world. If a foreign metal object enters the area between these two coils during wireless power transfer, fire hazards or equipment damage may occur. Therefore, we propose a method for detecting foreign metal objects in the gap between the transmitting and receiving coils in a wireless high-power transfer system. A resonant detection coil set is used to exploit the change induced in electrical characteristics when a foreign metal object is inserted. The mutual inductance of the foreign metal object changes the impedance of the detection coil set. We developed a simple circuit to detect both the magnitude and phase change of the voltage signal according to the altered impedance. Additionally, we implemented a prototype of a wireless power transfer system with a detection system to verify that even small foreign metal objects can be detected effectively.
Highlights
Bryan Pong and Gus Cheng ZhangThe application of wireless charging technologies, used in small devices, such as smartphones, laptops, and game consoles, to large devices, such as electric vehicles and robots, has been extensively researched [1,2,3]
In the wireless charging system proposed by the SAE J295 standard, BMW, and Hyundai Motors, the distance between the transmitting and receiving coils is found to be approximately 15–30 cm because the transmitting and receiving pads for wireless charging are located on the floor and under the vehicle, respectively [5,6]
Foreign object detection (FOD) technology is an essential function that must be practiced in industry organization standards, such as the Wireless Power Consortium and SAE International
Summary
Bryan Pong and Gus Cheng ZhangThe application of wireless charging technologies, used in small devices, such as smartphones, laptops, and game consoles, to large devices, such as electric vehicles and robots, has been extensively researched [1,2,3]. In the wireless charging system proposed by the SAE J295 standard, BMW, and Hyundai Motors, the distance between the transmitting and receiving coils is found to be approximately 15–30 cm because the transmitting and receiving pads for wireless charging are located on the floor and under the vehicle, respectively [5,6]. Such systems primarily use the magnetic resonance method, which allows power transmission to occur at a few meters. Foreign object detection (FOD) technology is an essential function that must be practiced in industry organization standards, such as the Wireless Power Consortium and SAE International
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