A comparative study on overall efficiency of two-dimensional wireless power transfer systems using rotational and directional methods

Abstract

Two-dimensional (2-D) wireless power transfer (WPT) systems can be controlled by either the directional method or the rotational method. The rotational method refers to the use of omnidirectional transmitter generating rotational flux regardless of the load positions, while the directional method refers to the use of omnidirectional transmitter generating magnetic flux directly toward the power-consuming load directions. This article compares the overall efficiency of the two methods for 2-D WPT systems. Theoretical analysis reveals that the directional WPT can be more efficient than the rotational WPT with either single or multiple loads when the magnetic field vector is controlled within the feasible zones; and the efficiency difference between the two methods are more significant when the dimensions of the receiver coils are smaller. Both simulation and experimental results are consistent in validating the two discoveries. They indicate that the averaged efficiency of the directional method is at least 5% higher than that of the rotational one.