Wireless power transmission based on the double two-way spiral coil

Magnetically coupled resonant (MCR) wireless power transmission (WPT) has the advantages of high efficiency, large transmission power and so on. It is suitable for medium-distance power supply. However, the traditional MCR WPT system based on the single one-way spiral coil (SOSC) will suffer frequency splitting due to the over-coupling between the transmitting and receiving coils during short-distance transmission. After analyzing the effect of coupling coefficient on the transmission efficiency of such systems, this paper proposed a double two-way spiral coil (DTSC) design method. This method used the structural features of the designed spiral coil to counteract the increased coupling coefficient due to short-distance transmission, thereby weakening the over-coupling between the transmitting coil and the receiving coil, narrowing the over-coupling region of the system, and compensating the effect of frequency splitting on the transmission efficiency during short-distance WPT. This method narrowed the system’s frequency splitting region and improved the system’s short-distance transmission efficiency. This paper analyzed the effect of the inner and the outer radius, the number of turns, and the pitch of the DTSC on the efficiency of the WPT system. This study showed that compared with the WPT system based on the SOSC, the WPT system based on the DTSC could narrow the frequency splitting region and significantly improve the short-distance transmission efficiency of the system. The correctness of the theoretical analysis has been verified by simulations and experiments.