A wireless power transfer device includes an inverter configured to convert DC input to an AC waveform that drives a resonant circuit, a primary coil configured to generate a magnetic field, a shield material placed below the primary coil, a current sensor configured to monitor current in the primary coil, and a communications and control unit configured to communicate with a wireless power receiver device and control power transfer, wherein the primary coil consists of a single layer of which a number of turns is 12, and consists of 105 strands Litz wire of which the diameter is 0.08 mm, wherein the shield material is at least 1.5 mm thick and extends at least 2.5 mm beyond the outside of the primary coil, and wherein the primary coil and the shield material has a self-inductance 10.0 μH.