Inductive power transfer apparatus
An IPT system magnetic flux pad includes two substantially planar coils ( 17 ) in close proximity to each other above a magnetically permeable core ( 14 ). The coils ( 17 ) each define a pole area ( 11, 12 ) and the distance between one or more adjacent turns of the coils ( 17 ) located in a region between the pole areas ( 11, 12 ) being different from the distance between one or more adjacent turns of the coils ( 17 ) located outside the region between the pole areas ( 11, 12 ).
1. A device configured to generate or receive magnetic flux, the device comprising two substantially co-planar coils in close proximity to each other, and a magnetically permeable core, wherein the two substantially co-planar coils are series wound from a length of wire and magnetically associated with core.
2. The device of claim 1 , wherein the device comprises a third substantially planar coil, and the third substantially planar coil overlaps the two substantially co-planar coils.
3. The device of claim 2 , wherein the two substantially co-planar coils and the third substantially planar coil are parallel tuned for resonance at a single frequency.
4. The device of claim 2 , wherein two substantially co-planar coils each define a pole area, and the third substantially planar coil overlaps the pole areas of the two substantially co-planar coils.
5. The device of claim 2 , wherein the third substantially planar coil is wound from wire, and the third substantially planar coil has about the same number of turns as the two substantially co-planar coils.
6. The device of claim 1 , wherein the device is configured to reflect an impedance onto an inductively coupled pad that compensates for a change in the inductance in the inductively coupled pad caused by the device.
7. The device of claim 1 , wherein the two substantially co-planar coils are wound from a single length of wire.
8. The device of claim 1 , wherein the two substantially co-planar coils are partially series compensated to compensate for variations in alignment between the device and an inductively coupled pad.
9. A device comprising two substantially planar coils in close proximity to each other, wherein the two substantially planar coils each define a pole area, and the device comprises a magnetically permeable core extending between the pole areas, wherein turns of the two substantially planar coils that are located in a region between the pole areas are more closely magnetically associated with the magnetically permeable core than turns of the two substantially planar coils located outside the region between the pole areas.
10. The device of claim 9 , wherein the device comprises a third substantially planar coil, and the third substantially planar coil overlaps the two substantially planar coils.
11. The device of claim 10 , wherein the third substantially planar coil is in spatial quadrature to the two substantially planar coils.
12. The device of claim 10 , wherein the two substantially planar coils and the third substantially planar coil are wound from wire, and windings of the third substantially planar coil pass through the center of each of the two substantially planar coils.
13. The device of claim 10 , wherein the two substantially planar coils and the third substantially planar coil are tuned to resonate at the same frequency.
14. The device of claim 9 , wherein the two substantially planar coils are connected in series.
15. The device of claim 9 , wherein the device is configured to have an uncompensated power that is substantially the same around a defined radius of misalignment of the device with an inductively coupled pad.