As wireless wireless power transfer systems getting widely used, the loss of energy due to coil offset needs to be solved urgently. Changing the coil structure, which can affect the magnetic field, is a generally adopted method and research hotspot. ANSYS Maxwell is used for simulation, both typical and newly-designed coil model, in order to research the influence on mutual inductance coefficient when coil moves and observe the excited magnetic field distribution. The wireless charging circuit with new coil can verify the result after experiment and calculation. Offset effect at uniform magnetic field is verified that it is relatively small, but the magnetic field of classical cross coupling coil is not uniform as expected. The newly-designed quadruple-connected cross coupling coil achieves a range of uniform magnetic field in the center and less change mutual inductance coefficient while offsetting (see Figure 1). The new coil reduces the loss of transmission efficiency while offsetting, which can be used when the position of coil cannot be accurately controlled, like wireless charging of electric vehicles. It also has potential to realize wireless charging of multiple mobile phones at one port.

Wireless power transfer.,coupling coil,offset,coil structure,Electromagnetic field simulation