In this study, a high-efficiency wireless power transfer (WPT) coil that is robust against interoperability and misalignment was developed by applying an inductive power transfer system to a drone. The transmitting coil had a ferrite plate applied to a helical structure that included the receiving part. The receiving coil was a guard-type receiving part applied to the ferrite sheet. To analyze the spiral and helical coils according to the winding method, the z-axis magnetic field vector was analyzed. A suitable WPT model was developed for each drone by analyzing the mutual inductance based on whether the ferrite was attached to the transmitter or receiver and the ferrite sheet's location. The electrical characteristics of the coil were derived using Ansys Electronics Maxwell, and a comparative analysis was performed using the measured values of the fabricated coil. The mutual inductance change due to misalignment between the coils of the transmitter and receiver of the proposed model was analyzed. It was demonstrated that the magnetic field distribution was uniform according to the misalignment error.

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