Design Of Power Transmission System In Complex Metallic Environment

Combined with the key project of application and development of Chongqing “The key technology and design of RFID system in complex metallic environment”, this paper designed wireless power transmission system in complex metallic environment. The designed system is also called inductive power setting system, which transmits power through electromagnetic coupling among transmitting coil and receiving coil. To realize wireless power transmission with larger power in metallic environment, this paper mainly set to study from three parts, such as the circuit design of wireless power transmission system, the design of transmitting coil and receiving coil, and the influence of metallic environment on power transmission. The main works in this paper include:According to the real work situation of the project, the design plane for inductive power setting system was determined and the circuit design was completed. This paper proposed a new design scheme based on Royer oscillator for inductive power setting system, determined the structure of transmitting coil and the operating frequency, according to the system requirements that the energy storage capacitor of 200 u F is charged to 13 V in 65 milliseconds while the receiver and transmitter are 3cm apart in complex metallic environment. The transmitter generates AC voltage with enough power after self-excited oscillation and power amplifier. The AC voltage drives the transmitting coil to produce alternating magnetic fields. The receiving coil in the alternating magnetic field produces an AC voltage on the same frequency by induction, and then it is converted into DC voltage through rectifier and voltage regulator circuit to charge the energy storage capacitor. It has been verified from the simulation and measurement that the designed system circuit meets the requirement of the system.The transmitting coil was designed. In order to improve the energy coupled by receiving coil as much as possible, we should increase magnetic induction at the position of receiving coil. Because the transmitting coil and receiving coil cannot be coaxial, so this paper adopted axis-curved spiral coil with magnetic core as the transmitting coil. The results of MATLAB simulation and Finite-element analysis by Ansoft indicate that axis-curved spiral coil as the transmitting coil can enhance the magnetic field at the receiving coil and improve the power efficiency of the system. Moreover, the axis-curved spiral transmitting coil with cobalt-based amorphous alloy magnetic core can largely enhance the magnetic field around it.This paper presented the design method of the best coil turns of receiving coil. As the receiving coil locates in the metallic cavity, its position and size are limited. Simulation results by MATLAB show that the receiving coil has a best inductance for the maximum under the same situation at the transmitter. When the resonant frequency of the system is certain, the best value is only confirmed by the resistance of receiving coil and load resistance. Meanwhile, this paper analyzed the effects of the parameter of receiving coil on resistance and inductance, and the effect on received voltage, such as the diameter of receiving coil and the diameter of its wire, and later presented that when the diameter of receiving coil and its wire is certain, we can determine the maximum of the received voltage through by determining the coil turns.The metallic material of the fuse was determined. Because metal will produce eddy current in the high frequency magnetic field, the coil wire will generate skin effect, which makes AC resistance of coil is higher than its DC resistance, and increases power loss of the system. Besides, the eddy current effect of metal will absorb a part of electromagnetic wave in complex metallic environment. Absorption of electromagnetic wave on four metals like aluminum, iron, silver, and stainless-steel is different, among them iron has much greater power loss than other several metals, followed by stainless-steel, and then aluminum and silver, So we choose aluminum as the metal material of the fuse or the material plated with silver. But the eddy current produced by induction in stainless-steel plate is lowest, so the reaction on magnetic field of original coils in it is also smallest and there is a largest reaction in iron plate, and it is perfectly acceptable used stainless-steel as metal material of the metallic cavity.According to the theoretical analysis and simulation results, a wireless power transmission with larger power in complex metallic environment was designed in this paper, which was made of the system circuit based on the topology structure of Royer oscillator, the axis-curved spiral transmitting coil with the cobalt-based alloy core, the receiving coil that is designed to the optimal turns and the metal material of the fuse with the lowest absorption of electromagnetic wave was choose. It has been verified from experiments that the designed system meets the requirements proposed in the project and achieves the expected goal.