Study on the Influence of the Magnetic Field and the Induced Electrical Field in Human Bodies by EV/PHEV Wireless Charging Systems

Wireless charging systems for electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) employing the resonant magnetic coupling method and using induction coils have been intensively studied in recent years. Since this method requires kW class high power to be transmitted using resonant magnetic coupling in the high frequency range, it is necessary to pay attention to the leakage of the magnetic field generated by the coil current, and to its influence on surrounding objects, particularly human bodies. Noting that acceptable values for human body exposure to electromagnetic fields have previously been issued by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) as guidelines, we have developed a method for predicting product compliance with those guidelines at the basic design development stage. This method calculates the magnetic field generated by the induction coil current and predicts the value of the electric field induced in the human body. Once we calculate the surrounding magnetic field of the vehicle, this method makes it possible to evaluate induced electric field values when a human body is present in various locations. Using this method, we analyzed the magnetic field distribution and electric field of a 3.7 kW charging system operating at a resonant frequency of 85 kHz while taking into consideration induction coil positions under, at the rear, at the center, and in front of the vehicle. The results show that the induced electric field in the human body is much smaller than the basic restrictions imposed by the ICNIRP guidelines.