Wireless power transfer (WPT) system for an electric vehicle (EV): how to shield the car from the magnetic field generated by two planar coils
This paper deals with the numerical evaluation of the magnetic field emitted by a wireless power system (WPT) in an electric
vehicle (EV). The numerical investigation is carried out using a finite element method (FEM) code with a transition boundary
condition (TBC) to model conductive materials. First, the TBC has been validated by comparison with the exact solution in
simple computational domains with conductive panels at frequencies used in WPT automotive. Then, the FEM with TBC has
been used to predict the field in an electric car assuming the chassis made by three different materials: steel, aluminum, and
fiber composite. The magnetic field source is given by a WPT system with 7.7 kW power level operating at frequencies of 85 or
150 kHz. The calculated magnetic field has been compared with the International Commission on Non-Ionizing Radiation
Protection (ICNIRP) reference level demonstrating compliance for an EV with metallic (steel or aluminum) chassis. On the
contrary, a fiber composite chassis is much more penetrable by magnetic fields and the reference level is exceeded.