Attenuation of Stray Magnetic Field in Inductive Power Transfer by Controlling Phases of Windings' Currents

Significant stray magnetic field exists around the inductive-power-transfer (IPT) coils owning to the large gap between transmitter and receiver. In this paper, the field is attenuated by controlling the phases of windings' currents. The relationship between magnetic field and windings' currents is analyzed according to the diagrams of phasors. The dual-side-controlled converter is used for circuit realization, in which the inverter and rectifier with MOSFETs bridges are implemented on both the transmitter side and receiver side. The pulsewidths of the voltages for the inverter and rectifier control the currents magnitudes, whereas the phases of the voltages control the currents phases. The effectiveness of field attenuation with this method was verified in both simulation and experiment, for the IPT system with series-series compensation. The stray magnetic field was reduced by up to 30% when the phase difference is 50 degrees between transmitter current and receiver current, compared to the conventional case with passive rectifier when the phase difference is 90 degrees. The increase of winding losses is also analyzed.