Field attenuation around inductive-power-transfer coils with dual-side-controlled converter

The stray magnetic field around inductive-power-transfer coils is influenced by the phases of the transmitter's and receiver's currents. This influence is analyzed with the diagrams of phasors for the currents and magnetic fields. The dual-side-controlled converter is applied for the circuit realization, in which the bridges with MOSFETs are used for the inverter on the transmitter side and rectifier on the receiver side. The magnitudes of windings' currents are controlled by the pulse-widths of the inverter voltage and rectifier voltage, and the currents' phases are controlled by the phases of the voltages. The field attenuation of this method was verified in finite-element simulation, with a series-series inductive power transfer system designed for 3.3 kW power transfer. In the conventional case with passive rectifier, the phase difference is 90° between the currents of transmitter and receiver. When the phase difference is decreased to 50° using the dual-side-controlled converter, the stray magnetic field is reduced by up to 30%.