Analysis of Modified Tri-axial Circular Helmholtz Coil in Wireless Power Transfer System

Stable and high-efficiency transmission performance is of great significance for wireless power transfer (WPT) system. Despite of some approaches, such as improving the quality factor (Q), regulating current distribution and achieving the impedance matching, can minimize the unfavorable influence and improve the system performance, the uniformity of electromagnetic field need further consideration. This paper proposes a modified spatial tri-axial circular Helmholtz coil (MTHC) to shape the homogeneous magnetic field over a large range in the three-dimensional direction of space so as to improve the flexibility of receiving coil position. The designed MTHC coil is to add a pair of compensation coils on each dimension. And the structural characteristics of the traditional Helmholtz coil, the improved compensated Helmholtz coil, and the spatial Tri-axial circular helmholtz coil are analyzed through theory and simulation, results show that the traditional Helmholtz coil structure has a uniform magnetic field area on the coaxial axis, but the uniform magnetic field area is small; the improved four-coil Helmholtz structure increases the uniform magnetic field area on the coaxial axis; the designed spatial Tri-axial circular Helmholtz coil structure is in the three-dimensional direction generating a wide uniform magnetic field.