The Electromagnetic Field of a High-Power, Air-Core DD Coupler for DWPT

Dynamic wireless power transfer (DWPT) requires a track in lieu of the single primary or ground assembly (GA) used in static wireless power transfer. The track is embedded in the roadway and is subject to repetitive stress from vehicles traveling over it, thermal cycling, moisture, and chemical exposure, especially de-icing agents. Therefore, some DWPT tracks employ couplers without ferrite cores despite the performance improvement ferrite provides. The DD coupler is widely used as a GA coupler for such DWPT systems. The original design of the DD coupler employed a flat ferrite core backed by a conducting plate to implement a so-called single-sided coupler. Here, we analyze the effect of eliminating the magnetic core and the backing conductive plate from the DD coupler. It is shown that the equivalent multiple representation of the DD coupler changes markedly with the removal of the ferrite core and further with the removal of the conducting plate. It is shown that not only is the magnetic coupling is diminished, but additionally the nature of the extraneous electromagnetic field is fundamentally altered. A new approach is given for recovering the ferrite-driven performance, based on replacing the Amperian currents representing the ferrite with a third winding.