Innovative 5-m-Off-Distance Inductive Power Transfer Systems With Optimally Shaped Dipole Coils

5-m-off-distance inductive power transfer systems that have optimally shaped cores in the primary and secondary coils are proposed. Instead of conventional-loop-type coils for magnetic resonance scheme, magnetic dipole type coils with cores are used for drastic reduction in deployment space and quite long wireless power transfer. An optimized stepped core structure is also proposed, where a strong magnetic field section is so thick that magnetic field density may be even. Thus, the proposed optimized stepped core has only 41% core loss compared with an unoptimized even core but delivers 2.1 times more wireless power for a given amount of core. Experimentally obtained maximum output powers and primary-coil-to-load-power efficiencies for 3, 4, and 5 m at 20 kHz were 1403, 471, 209 W, and 29%, 16%, 8%, respectively.