Modeling and experimentation of loosely-coupled coils with transmitter having orthogonally-placed windings

It is sometimes unavoidable to use loosely-coupled coils in applications, such as biomedical devices, for transferring electric energy wirelessly. However, coil misalignment would cause unwanted degradation of the power transfer efficiency. A coil structure that consists of two orthogonally-placed windings in the transmitter is investigated in this paper. Such structure lessens the variation of the coupling between the transmitting and receiving coil sets under the misalignment situations. A driving mechanism for maximizing the power transfer efficiency will be discussed. An experimental prototype has been built and evaluated under lateral and angular misalignments. Experimental results confirm the merits and are in close agreement with the theoretical predictions.