In this paper, a three dimensional multi-load wireless power transfer (WPT) system is designed and optimized for the sensor network which has the characteristics of large number, low power consumption, and wide spatial distribution. Firstly, a new structure of three-dimensional multi-load WPT system is proposed and its circuit model is established, and the influencing factors of transmission efficiency and power are analyzed. Then, the magnetic coupling structure is specifically designed, and a toroidal spiral coil structure is proposed, which is used as repeating coil and several receiving coils nested to form the receiving side. The magnetic field simulation of the new coil structure is analyzed by Ansys. The 3D WPT system prototype can transmit power up to 2 W at a transmission distance of 20 cm. When the receiving side is connected to a single load, the maximum transmission efficiency is 44%, and the fluctuation of transmission efficiency with revolution is reduced by changing the current phase, and the energy transmission blind area is eliminated. When the receiving side is connected to multiple loads, the output power of each load reaches 2 W at 92% test points in the spherical space of the transmitting side, which meets the power consumption requirements of the sensor equipment. [ABSTRACT FROM AUTHOR]

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