Metal Object Detection in a Wireless High-Power Transfer System Using Phase-Magnitude Variation

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.

Automated summary

Research on wireless charging technologies for large moving objects like electric vehicles and robots has led to the proposal of a method to detect foreign metal objects in a wireless high-power transfer system, using a resonant detection coil set to exploit changes in electrical characteristics. This research successfully developed a simple circuit to detect both magnitude and phase changes in voltage signal, and implemented a prototype of a wireless power transfer system with a detection system to effectively detect even small foreign metal objects.