The transmitting and receiving coils used in wireless power transfer (WPT) systems in electric vehicles (EVs) have a larger air gap (~300 mm) and higher transmission power (kW) than those in typical WPT systems used in electrical appliances. However, this could weaken the magnetic field, reduce transfer efficiency, and lead to a public concern regarding potential adverse health effects related to electromagnetic field (EMF) exposure. Therefore, the assessment of compliance with product safety standards, based on international exposure guidelines such as the International Commission on Non-Ionizing Radiation Protection (ICNIRP), is crucial. This study uses the finite element method to analyze a commonly used core-less and core-based WPT system using a composite core material in EVs and scalar potential finite difference method for assessment of human protection. Based on the computational results, two core structures using different types of intermediate insert blocks were analyzed to reduce external magnetic fields and mitigate the human EMF exposure. The WPT system with a core structure improved the transfer efficiency by 34% for a 300 mm air gap over the core-less system. Moreover, this effectively reduced magnetic field leakage by 91.6% and induced electric field by 98.3%, resulting in the reduction of induced electric field in anatomical human body model. The results demonstrated that a WPT system with a composite core can simultaneously improve the transfer efficiency and protect humans from EMF exposure.

Wireless power transfer (WPT) systems have attracted considerable attention in relation to providing a reliable and convenient power supply. Among the challenges in this area are maintaining the performance of the WPT system with the presence of a human body and minimizing the induced physical quantities in the human body. This study proposes a magnetic resonant coupling WPT (MRC-WPT) system that utilizes a resonator with a grounded loop to mitigate its interaction with a human body and achieve a high-efficiency power transfer at a short range. Our proposed system is based on a grounded loop to reduce the leakage of the electric field, resulting in less interaction with the human body. As a result, a transmission efficiency higher than 70% is achieved at a transmission distance of approximately 25 cm. Under the maximum-efficiency conditions of the WPT system, the use of a resonator with a grounded loop reduces the induced electric field, the peak spatial-average specific absorption rate (psSAR), and the whole-body averaged SAR by 43.6%, 69.7%, and 65.6%, respectively. The maximum permissible input power values for the proposed WPT systems are 40 and 33.5 kW, as prescribed in the International Commission of Non-Ionizing Radiation Protection (ICNIRP) guidelines to comply with the limits for local and whole-body average SAR.