Rotational Magnetic Field Regulation Featuring High Spatial Freedom for Wireless Power Transfer System

In this paper, a dual-input single-output high spatial freedom wireless power transfer system (WPT) is proposed, in which two orthogonal DD coils with the same size are used as the planar transmitting coil. Based on circuit modeling, the transfer characteristics of the proposed system are investigated. It is found that the stable equivalent mutual inductance can be achieved by designing the phase difference of the excitation current of the two transmitting coils. When the phase difference is π/2, the magnetic field trajectory of the transmitting coil is an ellipsoid, and the magnetic field captured by the receiving coil is uniform. Six rotation modes of the receiving coil are considered, including fixed-radius and variable-radius rotation patterns, and the impact of rotation angle is studied. Simulation results demonstrate that fluctuation of the equivalent mutual inductance is small when the receiver rotates at the six different modes. Experimental verification is carried out and the result shows that the output stability can be well kept when the receiving coil rotates in the range of [0°, 360°] at mode 1, mode 2, and mode 3. The output voltage can remain stable at 92 V, accompanied by a maximum efficiency of 87% in mode 1.