A z-Axis-Tolerant Inductive Power Transfer System Using a Bipolar Double D Receiver Coil Structure

Abstract

This paper presents a solution to a limitation of wireless power transfer that arises when using two D-shaped transmitter and receiver coils. Double D, or DD, coils are well known to have a polar, directional magnetic field, which increases the misalignment tolerance in one of the directions. The misalignment tolerance is nonsymmetric, and it is significantly better in one of the directions, which can also be considered a shortcoming. An additional shortcoming of the DD coil is that it is dependent on the rotation around the z-axis, due to the directional magnetic field. This is not a problem when using classic planar spiral coils, which do not generate a directional magnetic field. Therefore, DD coils are not suitable for applications in which the z-axis orientation is not determined and fixed to specific angle and direction. This paper presents a unique design of a transmitter coil, based on a double DD coil. The transmitter coil consists of two DD coils which are perpendicular to each other. The proposed transmitter structure can excite the receiver DD coil in a way that the efficiency of the power transfer is the highest, regardless of the orientation. The proposed transmitter structure can, therefore, solve the problem with rotation of a single DD coil. The proposed system structure was tested on the small-scale experimental setup.