Contents I. Introduction
In recent years, wireless power transmission (WPT) technology using magnetic resonance coupling has attracted much attention [1]. Accordingly, research and development of dynamic wireless power transfer (DWPT) have been actively conducted, and it is expected to solve the problems such as high cost and cable charging of electric vehicles [2]~[8]. Transmitter coils for DWPT utilizing magnetic field resonance are often used in rectangular circular coils, in which the conductors winding in a spiral shape. In contrast, DD coils, which look like two D's in the alphabet, are also used [9]~[12]. These coils are connected to external resonant capacitors to adjust the operating frequency to the international standard of 85 kHz band. The resonant capacitor must have a high withstand voltage due to the high voltage applied in DWPT. This is a factor that increases the cost of the transmitter coil units. The elimination of the resonant capacitors also reduces the number of components in the transmitter coil units, which is advantageous from an infrastructure standpoint because it reduces the risk of failure. Previous studies have proposed 85 kHz self-resonant coils that do not require external resonant capacitors [13]~[15]. Thus, although various types of coils have been proposed for transmitter coils in DWPT, no comparative investigation of the circular coil, DD coil, and 85 kHz self-resonant coil has been conducted, and no evaluation under actual road conditions has been found. Therefore, this study compares these three types. Evaluate under ideal conditions on the ground side and under road conditions. Based on these evaluation results, an excellent coil is selected.
