Influence Mechanism of Ferrite Foreign Object on Wireless Power Transmission System

In recent years, wireless power transfer (WPT) technology has entered the application stage. However, the inevitable presence of foreign objects (FO) in the magnetic coupling area during the operation of WPT systems, especially ferrite FO, may result in system detuning and safety incidents. To address this issue, this paper studies the mechanism by which the ferrite FO affects the WPT systems, providing a foundation for the future development of an FO detection device. Using a series–series topology WPT system as an example, a loop model incorporating ferrite FO is first developed to analyze the impact on the output power (OP) and transmission efficiency (TE) when the ferrite FO enters the magnetic coupling area. A 3D electromagnetic field simulation model of the magnetic coupling mechanism is then developed using finite element simulation software to study the impacts of FO of different sizes and positions within the magnetic coupling area on the WPT system. Finally, an experimental platform is constructed for experimental analysis and validation. An approach to detect the ferrite FO is provided by measuring the input power (IP) and TE. The WPT system is protected immediately by shuting down the transmitter if IP and TE sharply change over 15% in a few seconds.