| The application of wireless sensor network(WSN) can greatly improve the monitoring level of the coal mine. However, the stability of wireless sensor network is constrained by the battery capacity of wireless sensor nodes. Currently, the wireless power transfer(WPT) based on magnetic coupling resonance has been developed rapidly. The advantages of this new technology are cableless, long transfer distance and high security, which make it possible to charge the wireless sensor nodes.This paper briefly introduced the basic principle of WPT with two resonance coils. The transmission characteristics and the disadvantages in the application of the system were also analyzed. In order to increase the transmission distance and improve the received power, the WPT model with four resonance coils was established. First, the expression of the received power and the transmission efficiency were derived by the detail analysis of equivalent circuit of the WPT model and the usage of circuit coupling principle. Then, the key factors that affect the received power and transmission efficiency were simulated. The simulation results show that received power and transmission efficiency can’t reach the maximum value at the same situation and the input frequency affects the transmission characteristic greatly. At last, the improved circuit was discussed to reduce the influence of system frequency.According to the actual application, the improved wireless power transmission system was established. The influence factors such as transmission distance and coils deviation of received power and transmission efficiency were simulated and tested. The results show that the received power and the transmission efficiency can’t reach the maximum value at the same situation. The designed transmission system can get 5.6W, when the distance is 35 cm. The maximum transmission efficiency is 75% when the distance is 40 cm. |
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