Patent ID: 7239110

Claim:
A primary unit having a power transfer area in or over which a secondary device, separable from the primary unit, can be placed in a stationary working disposition to receive power from the primary unit without requiring direct electrical conductive contacts between the primary unit and the secondary device, the primary unit comprising: first and second field generators, each arranged substantially in parallel with said power transfer area and each configured so that if driven individually the generator generates an electromagnetic field having field lines which extend generally in a predetermined direction across at least part of said power transfer area and which have significant resolved components parallel to the power transfer area, said predetermined direction of said first field generator being different from said predetermined direction of said second field generator; and a driving unit for applying electrical drive signals to said first and second field generators such that the first and second field generators cooperate to generate, in or over said at least one part of the power transfer area, field lines which, when resolved onto the power transfer area, change in direction over time.