The extraneous electromagnetic field produced by a wireless power transfer system employing dd polarized couplers

Magnetic field wireless power transfer (WPT) systems for vehicular applications are rapidly becoming standardized in order to facilitate interoperability. One somewhat unconventional coupler (winding assembly) design, the DD topology, has been shown to provide good performance in terms of efficiency, maximum separation, and tolerance to misalignment. However, the extraneous electromagnetic field of this topology has not been extensively investigated. Therefore, we provide quantitative analysis of the extraneous electromagnetic field of a representative WPT system employing DD coupler designs as specified by the SAE in the J2954 TIR. It is shown that the DD coupler, like the more conventional solenoidal polarized coupler, primarily produces a horizontal magnetic dipole moment with the axis of the dipole coinciding with a line connecting the centers of the two constituent spiral windings. The dominant horizontal magnetic dipole moment is enhanced by conducting ground due to a constructive image. However, the fields of the DD coupler are somewhat more complex and contain higher-order magnetic multipoles. This causes the near field pattern to deviate from that of a pure horizontal magnetic dipole.