The Selection and Comparison of Multi-coil Wireless Power Transmission Solutions via Magnetic Resonances

Multi-coil links are generally introduced to improve the efficiency and extend the energy transmission distance. However, most of them are relay solutions which are equivalent to reduce the distance. In this paper, two kinds of 3- and three kinds of 4-coil links unchanging the energy transmission distance are proposed respectively. Among these links, by comparing the characteristics, the appropriate coil arrangements of 3-, 4-coil links are selected. Through analyzing the reflected impedance Z(R2), it is pointed out that 3-coil link improves the efficiency by increasing Z(R2) compared with 2-coil link, and the 4-coil link, remaining the increased reflected impedance ZR2 of 3-coil link, has another flexibility with the added power coil to adjust the efficiency and output power. Finally, two prototypes with different power levers are fabricated in the lab. The experimental results of the small power prototype can verify the analysis and comparison of efficiency, output power and voltage gain of 2-, 3-and 4-coil links. The big power prototype improves the efficiency from 50.0% in 2-coil link to 85.1% in 3-coil link with P-o = 508.8W and d(23)=25cm.