Magnetic shield
A magnetic shield for shielding adjacent coils of an ICPT system. One or more conductors are configured to distribute induced eddy currents from the surface of the shield to below the surface and thus reduce heating due to eddy currents. The magnetic shield may be employed to transfer power over rotary couplings, such as the shaft of a wind turbine.
1. An ICPT system including a transmitting coil and a receiving coil wherein at least one coil is at least partly shielded by a magnetic shield formed of a plurality of elongate insulated conductors wherein the shield has a surface which in use is exposed to an incident magnetic field and wherein the elongate insulated conductors are arranged to distribute eddy currents from said exposure along a path length that is long with respect to the size of the shield.
2. The ICPT system as claimed in claim 1 wherein the elongate insulated conductors have an average thickness of about 1 to 3 skin depths in a plane transverse to the surface cross section.
3. The ICPT system as claimed in claim 1 wherein the elongate insulated conductors are arranged in a generally circular path.
4. The ICPT system as claimed in claim 1 wherein the elongate insulated conductors are arranged in a generally spiral path.
5. The ICPT system as claimed in claim 1 wherein the elongate insulated conductors are arranged in a semicircle.
6. The ICPT system as claimed in claim 1 wherein the elongate insulated conductors are arranged in a curved sheet.
7. The ICPT system as claimed in claim 1 wherein the elongate insulated conductors are capacitively loaded.
8. The ICPT system as claimed in claim 1 wherein the elongate insulated conductors are inductively loaded.
9. The ICPT system as claimed in claim 7 wherein the magnetic shield is tuned to screen a magnetic field oscillating at a desired frequency.
10. The ICPT system as claimed in claim 9 in the form of a disc.
11. The ICPT system as claimed in claim 1 , wherein the at least one coil is at least partly shielded from its surrounds.
12. The ICPT system as claimed in claim 11 , wherein the at least one coil is at least partly shielded from surrounding metallic elements.
13. The ICPT systems as claimed in claim 12 , wherein the at least one coil is at least partly shielded from an adjacent coil.
14. A wind turbine including an ICPT system as claimed in claim 1 .