This paper introduces scaling-factor and design guidelines for shielded-capacitive power transfer (shielded-CPT) systems, offering a simplified design process, coupling-structure optimization, and consideration of safety. A novel scaling-factor-analysis method is proposed by determining the configuration of the coupling structure that improves system safety and increases operating efficiency while minimizing the gap between the shield and the coupler plate. The inductor-series resistance is also analyzed to study the loss efficiency in the shielded-CPT system. The relationship among the shield-coupler gap, distance between the couplers, conductive-plate size, and delivered power is examined and presented. The proposed method is validated by implementing the shielded-CPT system with hardware and the result suggests that the proposed method can be used to design shielded-CPT systems with scaling-factor and safety considerations.
A capacitive power transfer (CPT) system wirelessly transfers energy between coupling plates and performance issues related to CPT systems are resonance conditions, matching impedance, voltage stress, and power loss. A generalized circuit model is proposed for shielded capacitive power transfer (S-CPT) using an algebraic method. The proposed generalized S-CPT model is analyzed based on the symmetric and asymmetric configurations, and the relationship between the parameters of S-CPT is obtained with respect to the resonance condition, matching impedance, voltage stress, and efficiency. The best configuration of a symmetric S-CPT is recommended, and an asymmetric S-CPT is proposed based on the analysis results. Asymmetric-S-CPT hardware was constructed and demonstrated an operating frequency of 13.56 MHz. The hardware experimental result shows the validity and effectiveness of the proposed generalized model for designing S-CPT.
Grounding of electrical installation is primarily concern with ensuring safety. The main purpose of grounding is to channel the fault current straightly to earth. To produce a good grounding system, the value of earth resistance must be reduce as low as possible. Otherwise, current may flow through to those who touch the damage electrical equipment instead of flowing through grounding system. In this project, a variety diameter of copper rod and galvanized iron rod were installed to build grounding system. The aim of this project is to find if there exists significance difference in the value of resistance when different diameter and different type of rod were used. Single rod testing and parallel rod testing were performed with fall of potential method to measure the value of earth resistance. Result shows that different types of rod with different diameter size produce different resistivity value which also depends on installation technique and soil condition.
A preliminary study of Class-E radio frequency power amplifier for wireless capacitive power transfer (CPT) system is presented in this paper. Due to a limitation in coupling capacitance value, a high frequency operation of switching power inverter is necessary for the CPT system. A GaN MOSFET offers reliability and performance in a high frequency operation with an improved efficiency over a silicon device. Design specification related to the parallel load parameter, LC impedance matching and experimental analysis of the amplifier is explored. An experimental setup for the proposed inverter and its integration with the CPT system is provided, and the power efficiency is investigated. As a result, by utilizing a 6.78 MHz resonant frequency and a 50 Ω resistive load, 50 W of power has been transmitted successfully with an end to end system efficiency over 81 %. Additionally, above 17 W wireless power transfer was demonstrated successfully in the CPT system under 6 pF coupling with the efficiency over 70 %.
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