Evaluation of intermediate coils in IPT systems under magnetic coupler displacements

This paper evaluates the use of an intermediate coupler in a series-series resonant configuration under different magnetic coupler displacements via mathematical and simulation analysis. The circular design was selected and different intermediate coil arrangements were simulated using a 3D FEM software. A variable inductor (VI) is inserted in the transmitter circuit to compensate the extra reactance in a misaligned scenario. The use of a VI boosts the power transferred and keeps the switching losses in the transmitter inverter to a minimum. A new ferrite-less circular design with an intermediate coil is proposed with in an efficiency of 90.36% when transferring 4 kW over an air gap of 150 mm and with a horizontal displacement equivalent to 46% the diameter of the circular coupler. The inclusion of the VI, in the same conditions, boosts the power transferred by a factor of 8.94.