Wireless charger for electric vehicles

The wireless charging of electric vehicles can be accomplished with two different technologies:
  1. For the Inductive Power Transfer (IPT) one primary and one secondary coil as well as a rectifier are required. The primary coil is thereby located on the ground beneath the vehicle and fed by alternating current. Due to the generated alternating magnetic field an alternating voltage is induced in the secondary coil which is positioned underneath the vehicle. The rectifier then converts the AC power into DC power before storage. Sometimes the vehicle has to be lowered for the sake of a more efficient energy transmission.
  2. For Magnetic Resonance Coupling (MRC) four instead of two coils are necessary: each two are located underneath the vehicle and inside the vehicle. The outer coils with each one turn are brought into resonance by an oscillating current and consequently generate an oscillating magnetic field which induces a voltage in the two inner coils with multiple turns. Thereby the wireless charging process can be performed up to distances of ten times the diameter of a coil.
Typical measurement values can be found in the database of exposure sources.
Demonstration of wireless charging during parking at the Tokyo Motor Show 2011
photo: NJo, license: CC BY-SA 3.0, via Wikimedia Commons