Analysis of co-planar intermediate coil structures in inductive power transfer systems

Intermediate couplers have been shown to increase the coupling from primary to secondary pads in inductive power transfer (IPT) systems. This paper investigates embedding a co-planar intermediate coupler coil, with the primary coil inside the primary pad, to boost coupling to the secondary pad given there have been recent works indicating this will have similar benefits. Several coil designs are simulated and a mathematical model is developed to evaluate the efficiency of the parallel-parallel tuned system. As shown, there appears to be no benefit in having a co-planar, independently tuned intermediate coupler with parallelparallel tuned systems. Boosts in coupling and efficiency are a result of adding extra current carrying windings to the primary pad and simulations show that operating the system as a traditional two coil IPT system is simpler for the same performance. An experimental system was also constructed to validate the simulations.